Applied mineralogy in the study of historical lime mortars

8. Appendices: Published and Submitted Works 75 8.Appendices Published and Submitted Works (cc)2020 GRACIELA PONCE ANTON (cc by 4.0) Applied Mineralogy in the Study of Historical Lime Mortars 76 8. Appendices: Published and Submitted Works 77 APPENDIX I Accurate Mineralogical Characterization to Assess the Radiocarbon Dating of Historical Lime Mortars Applied Mineralogy in the Study of Historical Lime Mortars 78 8. Appendices: Published and Submitted Works 79 APPENDIX I.1 Hydrotalcite and Hydrocalumite in Mortar Binders from the Medieval Castle of Portilla (Álava, North Spain): Accurate Mineralogical Control to Achieve More Reliable Chronological Ages Graciela Ponce-Antón, Luis Angel Ortega, Maria Cruz Zuluaga, Ainhoa Alonso-Olazabal, Jose Luis Solaun Minerals 2018; 8(8):326 Applied Mineralogy in the Study of Historical Lime Mortars 80 8. Appendices: Published and Submitted Works 81 Article Metrics 9 Journal Citation Reports Citations: 1 Impact Factor 2018 5 Years 2.25 2.453 JCR® Rank Classification Quartile Percentile Mineralogy 12 of 29 Q2 60.345 Mining & Mineral Processing 6 of 19 Q2 70.053 9 Scopus Citations: 3 CiteScore 2018 2.46 SJR 2018 0.427 SNIP 2018 0.966 CiteScore Rank Classification Percentile Earth and Planetary Sciences (Geotechnical Engineering and Engineering Geology) 39 of 176 78 Earth and Planetary Sciences (Geology) 47 of 217 78 9 Google Academic Citations: 7 Applied Mineralogy in the Study of Historical Lime Mortars 82 minerals Article Hydrotalcite and Hydrocalumite in Mortar Binders from the Medieval Castle of Portilla (Álava, North Spain): Accurate Mineralogical Control to Achieve More Reliable Chronological Ages Graciela Ponce-Antón1,*ID , Luis Angel Ortega 1ID , Maria Cruz Zuluaga 1, Ainhoa Alonso-Olazabal 1and Jose Luis Solaun 2ID 1Department of Mineralogy and Petrology, Science and Technology Faculty, University of the Basque Country-UPV/EHU, Sarriena s/n, 48940 Leioa, Bizkaia, Spain; [email protected] (L.A.O.); [email protected] (M.C.Z.); [email protected] (A.A.-O.) 2Department of Geography, Prehistory and Archaeology, Faculty of Arts, University of the Basque Country-UPV/EHU, Paseo de la Universidad, 5, 01006 Vitoria-Gasteiz, Spain; [email protected] *Correspondence: [email protected]; Tel.: +34-946-015-456 Received: 8 June 2018; Accepted: 26 July 2018; Published: 29 July 2018 !"#!$%&'(! !"#$%&' Abstract: Mortars from different stratigraphic units at Portilla Castle (Alava, North Spain) have been analyzed for mineralogical characterization before radiocarbon dating. The mortar binder at Portilla Castle is composed not only of neoformation calcite but also of double-layered hydroxide (LDH) minerals such as hydrotalcite and hydrocalumite. The mineralogy of several fractions of the binder has been analyzed to determine the granulometric distribution of minerals in the binder. The continuous monitoring of mineralogy during the extraction of different grain size fractions has been performed by using a scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analyses (TGA). Hydrotalcite and hydrocalumite-bearing mortar binders give older ages than expected since they introduce dead carbon into the system. Keywords: mortar; binder; hydrotalcite; hydrocalumite; radiocarbon dating 1. Introduction One of the main goals in building archaeology is to determine the age of the structures discovered. In the absence of written records or other archaeological evidence to establish the chronology of the building, traditionally wooden timbers are used in radiocarbon dating [ 1 ]. Through this way, the date obtained may point to older ages due to material reuse or long storage. Therefore, it is vital to determine that the historical remains are not affected by the use of older construction materials since the reuse of wood materials leads to an in-built age defined as the difference between the time when the wood formed and the date of the event of interest [2–5]. In this framework, mortars can provide a potential dating solution. Archaeological mortars are artificial materials composed of a mixture of lime or plaster as binder and sand or other kinds of organic or inorganic additive as aggregates. The ease of preparation as well as the availability of raw materials and their durability have contributed to make mortars ubiquitous materials at sites from the Neolithic period onwards, which becomes an important source of information in archaeological sites [6,7]. Archaeological mortars have been dated by using radiocarbon methods since the 1960s as a way to determine the age of historical/archaeological structures. As such, the application of radiocarbon dating of mortars has been described by several authors [ 8 – 21 ]. Many studies have used charcoal Minerals 2018,8, 326; doi:10.3390/min8080326 www.mdpi.com/journal/minerals 8. Appendices: Published and Submitted Works 83 Minerals 2018,8, 326 8 of 17 Minerals 2018, 8, x FOR PEER REVIEW 7 of 16 fine fraction (<2 µm), magnesium calcite was identified as the main component of all samples while quartz, hydrotalcite [Mg6Al2(CO3)(OH)16·4(H2O)], and hydrocalumite [Ca4Al2(Cl,CO3,OH)2(OH)12·4H2O] are also present in minor amounts (Figure 5). The low intensity of hydrotalcite and hydrocalumite reflections indicates not only low abundance but also the low degree of crystallization of these mineral phases [49]. Figure 4. Photomicrographs showing the textural heterogeneity of historic lime mortars from Portilla Castle. (a) Mortar with rock fragments, lumps, and quartz grains. (b) Fragments of unburnt limestone and angular quartz grains. (c) Mortar with limestone fragments and quartz bearing lumps. (d) Mortar with a pure lump and charcoal fragment. Rx: rock fragment, Qtz: quartz, L: lump, U: unburnt, C: charcoal. Figure 5. X-ray diffraction patterns of extracted binder fractions. ( a ) Fine fraction, ( b ) ultrafine fraction, and ( c ) target fraction. HC: hydrocalumite, HT: hydrotalcite, Qtz: quartz, Mg-Cal: magnesium calcite. These LDH mineral phases are formed as a result of the slaking process and identification and characterization is crucial due to their very high ability to fix carbonate anions [ 68 ]. During the rehydration process, CO 32 from the partial washing of unburnt fragments of limestone is fixed in the crystalline structure of HT-like minerals. The captured CO 32 introduces dead carbon in the system and ages the radiometric dates. A new step was introduced in the extraction procedure in order to remove the potential contaminant HT-like mineral phases in the ultrafine fraction (<0.5 µm). SEM observations of fine fraction (<2 µ m) of the binder confirm the presence of very small HT-like particles embedded in a calcitic matrix (Figure 6). Irregular and hexagonal crystals of <0.5 µ m grain size, corresponding to Ca-enriched or Mg-enriched anion clays, can be observed in Figure 6b. The Energy Dispersive X-ray (EDX) analyses indicate that well-formed or euhedral crystals correspond to Ca-enriched HT-like particles (point 1 in Figure 7) while the irregular or anhedral crystals correspond to Mg-enriched HT-like particles (point 2 in Figure 7). Therefore, Ca-enriched particles correspond to hydrocalumite and Mg-enriched particles to hydrotalcite. In fact, hydrotalcite is more likely to be present as a non-well-formed phase compared with hydrocalumite [ 44 ]. The EDX analysis also shows the presence of silica that has been attributed to the presence of microcrystalline quartz. The SEM images of ultrafine fraction (<0.5 µ m) show a homogeneous matrix composed only of hydrotalcite and hydrocalumite phases of a <0.5 µ m grain size. The SEM-EDX analysis supports that the extraction of HT-like minerals from the fine fraction was successful (Figure 6c). Applied Mineralogy in the Study of Historical Lime Mortars 90 Minerals 2018,8, 326 9 of 17 Minerals 2018, 8, x FOR PEER REVIEW 8 of 16 Figure 5. X-ray diffraction patterns of extracted binder fractions. (a) Fine fraction, (b) ultrafine fraction, and (c) target fraction. HC: hydrocalumite, HT: hydrotalcite, Qtz: quartz, Mg-Cal: magnesium calcite. These LDH mineral phases are formed as a result of the slaking process and identification and characterization is crucial due to their very high ability to fix carbonate anions [68]. During the rehydration process, CO32− from the partial washing of unburnt fragments of limestone is fixed in the crystalline structure of HT-like minerals. The captured CO32− introduces dead carbon in the system and ages the radiometric dates. A new step was introduced in the extraction procedure in order to remove the potential contaminant HT-like mineral phases in the ultrafine fraction (<0.5 µm). SEM observations of fine fraction (<2 µm) of the binder confirm the presence of very small HT-like particles embedded in a calcitic matrix (Figure 6). Irregular and hexagonal crystals of <0.5 µm grain size, corresponding to Ca-enriched or Mg-enriched anion clays, can be observed in Figure 6b. The Energy Dispersive X-ray (EDX) analyses indicate that well-formed or euhedral crystals correspond to Ca-enriched HT-like particles (point 1 in Figure 7) while the irregular or anhedral crystals correspond to Mg-enriched HT-like particles (point 2 in Figure 7). Therefore, Ca-enriched particles correspond to hydrocalumite and Mg-enriched particles to hydrotalcite. In fact, hydrotalcite is more likely to be present as a non-well-formed phase compared with hydrocalumite [44]. The EDX analysis also shows the presence of silica that has been attributed to the presence of microcrystalline quartz. The SEM images of ultrafine fraction (<0.5 µm) show a homogeneous matrix composed only of hydrotalcite and hydrocalumite phases of a <0.5 µm grain size. The SEM-EDX analysis supports that the extraction of HT-like minerals from the fine fraction was successful (Figure 6c). Figure 6. Scanning Electron Microscopy images of binder mortar: (a,b) fine fraction and (c) ultrafine fraction. Point 1 and point 2 indicate the particles analysed by EDX. Figure 7. Energy dispersive X-ray analyses results of layered double hydroxides (LDH) of the fine fraction shown in Figure 6b. Point 1 is Ca-enriched anion clay (i.e., hydrocalumite) and point 2 is Ca-enriched anion clay (i.e., hydrotalcite). Petrographic, XRD, and SEM-EDX analyses show that the raw material used to obtain lime was impure limestone and/or partially dolomitized limestone. When limestones enriched in calcium magnesium are calcined, magnesium minerals should be considered in the mortar binder. Figure 6. Scanning Electron Microscopy images of binder mortar: ( a , b ) fine fraction and ( c ) ultrafine fraction. Point 1 and point 2 indicate the particles analysed by EDX. Minerals 2018, 8, x FOR PEER REVIEW 8 of 16 Figure 5. X-ray diffraction patterns of extracted binder fractions. (a) Fine fraction, (b) ultrafine fraction, and (c) target fraction. HC: hydrocalumite, HT: hydrotalcite, Qtz: quartz, Mg-Cal: magnesium calcite. These LDH mineral phases are formed as a result of the slaking process and identification and characterization is crucial due to their very high ability to fix carbonate anions [68]. During the rehydration process, CO32− from the partial washing of unburnt fragments of limestone is fixed in the crystalline structure of HT-like minerals. The captured CO32− introduces dead carbon in the system and ages the radiometric dates. A new step was introduced in the extraction procedure in order to remove the potential contaminant HT-like mineral phases in the ultrafine fraction (<0.5 µm). SEM observations of fine fraction (<2 µm) of the binder confirm the presence of very small HT-like particles embedded in a calcitic matrix (Figure 6). Irregular and hexagonal crystals of <0.5 µm grain size, corresponding to Ca-enriched or Mg-enriched anion clays, can be observed in Figure 6b. The Energy Dispersive X-ray (EDX) analyses indicate that well-formed or euhedral crystals correspond to Ca-enriched HT-like particles (point 1 in Figure 7) while the irregular or anhedral crystals correspond to Mg-enriched HT-like particles (point 2 in Figure 7). Therefore, Ca-enriched particles correspond to hydrocalumite and Mg-enriched particles to hydrotalcite. In fact, hydrotalcite is more likely to be present as a non-well-formed phase compared with hydrocalumite [44]. The EDX analysis also shows the presence of silica that has been attributed to the presence of microcrystalline quartz. The SEM images of ultrafine fraction (<0.5 µm) show a homogeneous matrix composed only of hydrotalcite and hydrocalumite phases of a <0.5 µm grain size. The SEM-EDX analysis supports that the extraction of HT-like minerals from the fine fraction was successful (Figure 6c). Figure 6. Scanning Electron Microscopy images of binder mortar: (a,b) fine fraction and (c) ultrafine fraction. Point 1 and point 2 indicate the particles analysed by EDX. Figure 7. Energy dispersive X-ray analyses results of layered double hydroxides (LDH) of the fine fraction shown in Figure 6b. Point 1 is Ca-enriched anion clay (i.e., hydrocalumite) and point 2 is Ca-enriched anion clay (i.e., hydrotalcite). Petrographic, XRD, and SEM-EDX analyses show that the raw material used to obtain lime was impure limestone and/or partially dolomitized limestone. When limestones enriched in calcium magnesium are calcined, magnesium minerals should be considered in the mortar binder. Figure 7. Energy dispersive X-ray analyses results of layered double hydroxides (LDH) of the fine fraction shown in Figure 6b. Point 1 is Ca-enriched anion clay (i.e., hydrocalumite) and point 2 is Ca-enriched anion clay (i.e., hydrotalcite). Petrographic, XRD, and SEM-EDX analyses show that the raw material used to obtain lime was impure limestone and/or partially dolomitized limestone. When limestones enriched in calcium magnesium are calcined, magnesium minerals should be considered in the mortar binder. Magnesium oxide (MgO) is formed as well as calcium oxide (CaO) during the calcination of dolomitic rocks due to the dolomitic cycle, which differs from the typical lime cycle (Figure 8). Considering that the LDH mineral phases constitute a potential contaminant in radiocarbon dating, the grain size fraction <0.5 µ m (i.e., ultrafine fraction) is extracted in order to eliminate these phases. XRD patterns of UF show significant increases of reflexions at d = 7.86 Å (11.2  2 ✓ ), d = 7.69 Å (11.4  2 ✓ ), d = 3.83 Å (23.2  2 ✓ ), and d = 2.58 Å (34.4  2 ✓ ) corresponding to hydrotalcite and indicate a large enrichment of LDH mineral phases in the ultrafine fraction (Figure 5b). As a result of the LDH minerals phase being removed, the target fraction (TF) corresponds to the grain size fraction between 0.5 µ m to 2 µ m. An XRD pattern of the TF fraction shows an increase in magnesium calcite reflections while hydrotalcite reflections disappear (Figure 5c). Nevertheless, an extraction procedure of the target fraction has to be checked in each mortar sample. Figure 9 shows XRD patterns of the target fraction of several samples. The presence and the intensity of characteristic reflections of LDH minerals in some XRD patterns suggest different levels of refinement in the extraction procedure, which indicates different amounts of LDH minerals in each sample. As can be observed, CP-2-TF, CP-4-TF, and CP-19-TF samples exhibit low intensity hydrotalcite reflections while CP-13-3-TF, CP-13-6-TF, CP-13-8-TF, and CP-13-10-TF samples still present significant LDH mineral reflections. 8. Appendices: Published and Submitted Works 91 Minerals 2018,8, 326 10 of 17 Minerals 2018, 8, x FOR PEER REVIEW 9 of 16 Magnesium oxide (MgO) is formed as well as calcium oxide (CaO) during the calcination of dolomitic rocks due to the dolomitic cycle, which differs from the typical lime cycle (Figure 8). Figure 8. Lime binder cycles. (a) lime cycle and (b) proposal of dolomitic lime cycle of impure dolostone. Considering that the LDH mineral phases constitute a potential contaminant in radiocarbon dating, the grain size fraction <0.5 µm (i.e., ultrafine fraction) is extracted in order to eliminate these phases. XRD patterns of UF show significant increases of reflexions at d = 7.86 Å (11.2° 2θ), d = 7.69 Å (11.4° 2θ), d = 3.83 Å (23.2° 2θ), and d = 2.58 Å (34.4° 2θ) corresponding to hydrotalcite and indicate a large enrichment of LDH mineral phases in the ultrafine fraction (Figure 5b). As a result of the LDH minerals phase being removed, the target fraction (TF) corresponds to the grain size fraction between 0.5 µm to 2 µm. An XRD pattern of the TF fraction shows an increase in magnesium calcite reflections while hydrotalcite reflections disappear (Figure 5c). Nevertheless, an extraction procedure of the target fraction has to be checked in each mortar sample. Figure 9 shows XRD patterns of the target fraction of several samples. The presence and the intensity of characteristic reflections of LDH minerals in some XRD patterns suggest different levels of refinement in the extraction procedure, which indicates different amounts of LDH minerals in each sample. As can be observed, CP-2-TF, CP-4-TF, and CP-19-TF samples exhibit low intensity hydrotalcite reflections while CP-13-3-TF, CP-13-6-TF, CP-13-8-TF, and CP-13-10-TF samples still present significant LDH mineral reflections. Table 2 summarizes the mineralogical assemblages and the semi-quantitative values (expressed in percentages) of identified phases in the ultrafine (<0.5 µm) and target (0.5 µm to 2 µm) factions. XRD results of target fraction show the persistent presence of LDH phases in small variable amounts in all samples. Nevertheless, XRD analysis does not always detect the presence of LDH phases when the amount remains near or under the detection limit. To check the extraction of the target fraction, even when the LDHs are not detected by XRD analysis, thermo-gravimetric analysis (TGA) is performed. Figure 8. Lime binder cycles. ( a )limecycleand( b )proposalofdolomiticlimecycleofimpuredolostone. Minerals 2018, 8, x FOR PEER REVIEW 10 of 16 Figure 9. X-ray diffraction patterns of target fractions of different mortar binders. HC: hydrocalumite, HT: hydrotalcite, Mg-Cal: magnesium calcite, Qtz: quartz. Table 2. Semi-quantitative data results (%) of X-ray diffraction analyses of target and ultrafine fractions of mortar binders. Sample Target Fraction (%) Ultrafine Fraction (%) Mg-Cal HT HC Qtz Total LDHs Mg-Cal HT HC Qtz Total LDHs CP-2 88 3 6 3 9 64 12 24 - 36 CP-4 84 8 8 - 16 58 16 26 - 42 CP-13-6 62 10 28 - 38 38 28 34 - 62 CP-13-8 79 9 10 2 19 48 28 24 - 52 CP-13-10 85 4 10 1 14 55 22 23 - 45 CP-19 89 5 5 1 10 55 24 20 - 44 CP-13-3 68 13 18 1 31 61 11 28 - 39 Mg-Cal: magnesium calcite, HT: hydrotalcite, HC: hydrocalumite, Qtz: quartz, LDHs: layered double hydroxides. The temperature ranges and relative weight loss observed in TGA analysis are reliable for the characterization of these materials. The first weight loss below 120 °C is attributed to the presence of adsorption water in the inter-particle pore. The second weight loss occurs between 120 and 200 °C and is attributed to the crystallization water or the interlayer water. The weight loss between 200 °C to 600 °C is attributed to structural OH−, which corresponds to the dehydration of the Ca(OH)2 of pure carbonates. Lastly, at temperatures above 600 °C, the loss of CO2 takes place due to the decomposition of the carbonate [69–71]. However, in the third decomposition step (200 °C to 600 °C) of target fraction (0.5 µm to 2 µm) from Portilla Castle samples, the TGA curve shows two weight loss steps (Figure 10). These weight losses correspond to the decomposition of LDH phases and are attributed to the loss of the OH− groups bonded to Al3+ and to Mg2+ in Mg-Al-CO3 compounds [72,73]. The thermos-gravimetric analyses of the target fraction show two different patterns, which are representative of TGA curves. These patterns are shown in Figure 10. The pattern type-A corresponds to samples with little weight loss in the 200 °C to 600 °C range (CP-2-TF, CP-4-TF, and CP-19-TF) while pattern type-B displays a pronounced stepped weight loss (CP-13-3-TF, CP-13-6-TF, CP-13-8-TF, and CP-13-10-TF). Table 3 summarizes the weight loss percentages of the target fraction in each temperature range. Samples show weight loss between 1.5% and 2.9% due to adsorbed Figure 9. X-ray diffraction patterns of target fractions of different mortar binders. HC: hydrocalumite, HT: hydrotalcite, Mg-Cal: magnesium calcite, Qtz: quartz. Table 2summarizes the mineralogical assemblages and the semi-quantitative values (expressed in percentages) of identified phases in the ultrafine (<0.5 µ m) and target (0.5 µ m to 2 µ m) factions. XRD results of target fraction show the persistent presence of LDH phases in small variable amounts in all samples. Nevertheless, XRD analysis does not always detect the presence of LDH phases when the amount remains near or under the detection limit. To check the extraction of the target fraction, even when the LDHs are not detected by XRD analysis, thermo-gravimetric analysis (TGA) is performed. Applied Mineralogy in the Study of Historical Lime Mortars 92 Minerals 2018,8, 326 11 of 17 Table 2. Semi-quantitative data results (%) of X-ray diffraction analyses of target and ultrafine fractions of mortar binders. Sample Target Fraction (%) Ultrafine Fraction (%) Mg-Cal HT HC Qtz Total LDHs Mg-Cal HT HC Qtz Total LDHs CP-2 88 3 6 3 9 64 12 24 - 36 CP-4 84 8 8 - 16 58 16 26 - 42 CP-13-6 62 10 28 - 38 38 28 34 - 62 CP-13-8 79 9 10 2 19 48 28 24 - 52 CP-13-10 85 4 10 1 14 55 22 23 - 45 CP-19 89 5 5 1 10 55 24 20 - 44 CP-13-3 68 13 18 1 31 61 11 28 - 39 Mg-Cal: magnesium calcite, HT: hydrotalcite, HC: hydrocalumite, Qtz: quartz, LDHs: layered double hydroxides. The temperature ranges and relative weight loss observed in TGA analysis are reliable for the characterization of these materials. The first weight loss below 120  C is attributed to the presence of adsorption water in the inter-particle pore. The second weight loss occurs between 120 and 200  C and is attributed to the crystallization water or the interlayer water. The weight loss between 200  C to 600  C is attributed to structural OH  , which corresponds to the dehydration of the Ca(OH) 2 of pure carbonates. Lastly, at temperatures above 600  C, the loss of CO 2 takes place due to the decomposition of the carbonate [ 69 – 71 ]. However, in the third decomposition step (200  C to 600  C) of target fraction (0.5 µ m to 2 µ m) from Portilla Castle samples, the TGA curve shows two weight loss steps (Figure 10). These weight losses correspond to the decomposition of LDH phases and are attributed to the loss of the OHgroups bonded to Al3+ and to Mg2+ in Mg-Al-CO3compounds [72,73]. Minerals 2018, 8, x FOR PEER REVIEW 11 of 16 water. The lower weight loss of water molecules from the interlayer space corresponds to type-A patterns and higher to type-B patterns. The weight loss between 200 °C and 600 °C temperature range corresponding to the dehydroxylation processes shows larger variations in the TG curves. Type-A pattern curves show weight loss varying from 10.3% to 12.8% while the weight loss in the type-B patterns varies from 13.6% to 19.6%. Weight loss in dehydroxylation processes shows larger contents of LDH minerals in the type-B samples than in samples with a type-A pattern. When over 600 °C, carbonates decompose and CO2 content ranges between 16.3% and 23.5%. The weight loss of pure calcium carbonate decomposition is 44% and lower percentages of weight loss indicate variable amounts of other compounds as LDH minerals. Therefore, mortars with no or little structurally-bound water (OH−) and high carbon dioxide content are potentially adequate for radiocarbon dating since they reflect the absence of other carbonate phases apart from calcite. Therefore, CP-2 and CP-19 are the most suitable mortars for radiocarbon dating since they display lower structurally-bound water and higher carbon dioxide content (Table 3). Figure 10. Thermo-gravimetric analyses of target fractions of representative mortar binders. (A) Binder samples with little weight loss and (B) binder samples with clear stepped weight loss in the 200 °C to 600 °C range. Table 3. Thermo-gravimetric analysis results (wt %) of target fractions of mortar binders. Sample Pattern Type H2O(Itp) H2O(Itl) OH− CO32− CP-2-TF A 1.46 1.35 10.40 23.47 CP-4-TF A 2.86 1.82 12.8 16.28 CP-13-6-TF B 2.30 2.78 19.64 18.46 CP-13-8-TF B 1.89 2.28 15.41 23.04 CP-13-10-TF B 1.89 2.12 17.01 21.83 CP-19-TF A 2.54 1.41 10.31 23.29 CP-13-3-TF B 2.77 2.45 13.56 18.06 Itp: interparticle, Itl: interlayer, TF: target fraction. Pattern type as referred in Figure 10. Since sample CP-19 shows the lowest weight loss of structurally-bound water corresponding to the decomposition of LDH phases, it has been selected instead of sample CP-2. In order to verify the contaminant potential of LDHs, both fine fraction (particle size <2 µm) and target fraction (particle size between 0.5 and 2 µm) have been dated (Table 4). The result of 14C dating of CP-19-FF is 2180 ± 40 BP corresponding to the calendar age of Cal BC 380–160 (Figure 11a) and the radiocarbon age of CP-19-TF is 1370 ± 30 BP, which corresponds to the calendar age of Cal AD 640–675 (Figure 11b). The obtained dates are older than expected since the first written chronicle of Portilla Castle is dated in 1040 AD. The age interval between the Figure 10. Thermo-gravimetric analyses of target fractions of representative mortar binders. ( A ) Binder samples with little weight loss and ( B ) binder samples with clear stepped weight loss in the 200  C to 600 C range. The thermos-gravimetric analyses of the target fraction show two different patterns, which are representative of TGA curves. These patterns are shown in Figure 10. The pattern type-A corresponds to samples with little weight loss in the 200  C to 600  C range (CP-2-TF, CP-4-TF, and CP-19-TF) while pattern type-B displays a pronounced stepped weight loss (CP-13-3-TF, CP-13-6-TF, CP-13-8-TF, and CP-13-10-TF). Table 3summarizes the weight loss percentages of the target fraction in each temperature range. Samples show weight loss between 1.5% and 2.9% due to adsorbed water. The lower weight loss of water molecules from the interlayer space corresponds to type-A patterns and higher to type-B patterns. The weight loss between 200  C and 600  C temperature range corresponding to the 8. Appendices: Published and Submitted Works 93 Minerals 2018,8, 326 12 of 17 dehydroxylation processes shows larger variations in the TG curves. Type-A pattern curves show weight loss varying from 10.3% to 12.8% while the weight loss in the type-B patterns varies from 13.6% to 19.6%. Weight loss in dehydroxylation processes shows larger contents of LDH minerals in the type-B samples than in samples with a type-A pattern. When over 600  C, carbonates decompose and CO 2 content ranges between 16.3% and 23.5%. The weight loss of pure calcium carbonate decomposition is 44% and lower percentages of weight loss indicate variable amounts of other compounds as LDH minerals. Therefore, mortars with no or little structurally-bound water (OH  ) and high carbon dioxide content are potentially adequate for radiocarbon dating since they reflect the absence of other carbonate phases apart from calcite. Therefore, CP-2 and CP-19 are the most suitable mortars for radiocarbon dating since they display lower structurally-bound water and higher carbon dioxide content (Table 3). Table 3. Thermo-gravimetric analysis results (wt %) of target fractions of mortar binders. Sample Pattern Type H2O(Itp) H2O(Itl) OHCO32 CP-2-TF A 1.46 1.35 10.40 23.47 CP-4-TF A 2.86 1.82 12.8 16.28 CP-13-6-TF B 2.30 2.78 19.64 18.46 CP-13-8-TF B 1.89 2.28 15.41 23.04 CP-13-10-TF B 1.89 2.12 17.01 21.83 CP-19-TF A 2.54 1.41 10.31 23.29 CP-13-3-TF B 2.77 2.45 13.56 18.06 Itp: interparticle, Itl: interlayer, TF: target fraction. Pattern type as referred in Figure 10. Since sample CP-19 shows the lowest weight loss of structurally-bound water corresponding to the decomposition of LDH phases, it has been selected instead of sample CP-2. In order to verify the contaminant potential of LDHs, both fine fraction (particle size <2 µ m) and target fraction (particle size between 0.5 and 2 µm) have been dated (Table 4). Table 4. Results of AMS 14C dates for different grain-size fractions of mortar binder. Lab Code Sample Binder Grain-Size Conventional Age 13CCalibrate Age (95.4%) BETA375404 CP-19-TF 0.5–2 µm 1370 ±30 BP 16.5 Cal AD 640–675 BETA343295 CP-19-FF <2 µm 2180 ±40 BP 21.3 Cal BC 380–160 TF: target fraction, FF: fine fraction. The result of 14 C dating of CP-19-FF is 2180 ± 40 BP corresponding to the calendar age of Cal BC 380–160 (Figure 11a) and the radiocarbon age of CP-19-TF is 1370 ± 30 BP, which corresponds to the calendar age of Cal AD 640–675 (Figure 11b). The obtained dates are older than expected since the first written chronicle of Portilla Castle is dated in 1040 AD. The age interval between the archaeological age and radiocarbon ages of the target fraction reflects the persistent presence of dead carbon contamination related with the CO32anion of hydrotalcite and hydrocalumite. Applied Mineralogy in the Study of Historical Lime Mortars 94 Minerals 2018,8, 326 13 of 17 Minerals 2018, 8, x FOR PEER REVIEW 12 of 16 archaeological age and radiocarbon ages of the target fraction reflects the persistent presence of dead carbon contamination related with the CO32−anion of hydrotalcite and hydrocalumite. Figure 11. Calibrated 14C dates of two fraction-sizes of the same lime mortar from Portilla Castle, (a) fine fraction (FF), and (b) target fraction (TF) obtained with OxCal v 4.1.7 [63] and IntCal09 atmospheric data [64]. Table 4. Results of AMS 14C dates for different grain-size fractions of mortar binder. Lab Code Sample Binder Grain-Size Conventional Age δ13C Calibrate Age (95.4%) BETA375404 CP-19-TF 0.5–2 µm 1370 ± 30 BP −16.5 Cal AD 640–675 BETA343295 CP-19-FF <2 µm 2180 ± 40 BP −21.3 Cal BC 380–160 TF: target fraction, FF: fine fraction. The mineralogical composition of carbonate phases of the mortar binder and the granulometric distribution has determined the particle size to be extracted for radiocarbon dating. The selection of fine-grain size fraction (<2 µm) is only useful when the mortar binder is formed solely by calcite, e.g., Ortega et al. [28]. In contrast, when the binder includes hydrotalcite and hydrocalumite besides neo-formation calcite, as in Portilla Castle, which determines the granulometric distribution of carbonate minerals is essential in selecting effective thresholds. Once the granulometric distribution is determined, the most suitable preconditioning method should be established for each sample in order to isolate the adequate fraction for radiocarbon dating. Therefore, dating of mortars without a comprehensive mineralogical study can lead to meaningless results. 5. Conclusions Portilla Castle mortars are formed by calcitic binder and quartz, limestone fragments, some partially dolomitized, and unburnt limestone remains as aggregates. The presence of hydrotalcite and hydrocalumite in the fine grain fraction of binder indicates the use of impure limestone and/or partially dolomitized limestones in the lime production. These raw materials provide magnesium and aluminium ions and under hyper-alkaline conditions lead to the formation of LDHs phases during the slaking process. The continuous mineralogical control of the extraction procedure allows a better mineralogical characterization of the finest grain fractions (<2 µm) of the binder. Only the study of these fractions allows the identification of hydrotalcite and hydrocalumite in lime mortars. In this contribution, additional steps in the extraction process to remove small grain size particles enriched in LDHs has been performed making the obtained radiocarbon dates closer to the archaeological ages. The occurrence of hydrotalcite and hydrocalumite mainly in the grain size is smaller than 0.5 µm in the Portilla Castle mortars, which adds dead carbon to the system and explains older ages than expected. Therefore, hydrotalcite and hydrocalumite constitute crucial contaminant mineral phases in mortar dating issues. Mineralogical studies are essential to select the samples for dating and reject unsuitable samples since they allow the mineralogical nature of the contaminants and the grain size distribution within Figure 11. Calibrated 14 C dates of two fraction-sizes of the same lime mortar from Portilla Castle, ( a ) fine fraction (FF), and ( b ) target fraction (TF) obtained with OxCal v 4.1.7 [ 63 ] and IntCal09 atmospheric data [64]. The mineralogical composition of carbonate phases of the mortar binder and the granulometric distribution has determined the particle size to be extracted for radiocarbon dating. The selection of fine-grain size fraction (<2 µ m) is only useful when the mortar binder is formed solely by calcite, e.g., Ortega et al. [ 28 ]. In contrast, when the binder includes hydrotalcite and hydrocalumite besides neo-formation calcite, as in Portilla Castle, which determines the granulometric distribution of carbonate minerals is essential in selecting effective thresholds. Once the granulometric distribution is determined, the most suitable preconditioning method should be established for each sample in order to isolate the adequate fraction for radiocarbon dating. Therefore, dating of mortars without a comprehensive mineralogical study can lead to meaningless results. 5. Conclusions Portilla Castle mortars are formed by calcitic binder and quartz, limestone fragments, some partially dolomitized, and unburnt limestone remains as aggregates. The presence of hydrotalcite and hydrocalumite in the fine grain fraction of binder indicates the use of impure limestone and/or partially dolomitized limestones in the lime production. These raw materials provide magnesium and aluminium ions and under hyper-alkaline conditions lead to the formation of LDHs phases during the slaking process. The continuous mineralogical control of the extraction procedure allows a better mineralogical characterization of the finest grain fractions (<2 µ m) of the binder. Only the study of these fractions allows the identification of hydrotalcite and hydrocalumite in lime mortars. In this contribution, additional steps in the extraction process to remove small grain size particles enriched in LDHs has been performed making the obtained radiocarbon dates closer to the archaeological ages. The occurrence of hydrotalcite and hydrocalumite mainly in the grain size is smaller than 0.5 µ m in the Portilla Castle mortars, which adds dead carbon to the system and explains older ages than expected. Therefore, hydrotalcite and hydrocalumite constitute crucial contaminant mineral phases in mortar dating issues. Mineralogical studies are essential to select the samples for dating and reject unsuitable samples since they allow the mineralogical nature of the contaminants and the grain size distribution within the binder to be determined. Mineralogical studies of the binder have to develop tailored purification procedures for each sample. Author Contributions: L.A.O. and M.C.Z. conceived and designed the experiments; J.L.S., G.P-A. and L.A.O. selected archaeological materials, G.P.-A. performed the experiments; G.P.-A., L.A.O. and M.C.Z. analyzed the data; A.A.-O. contributed to the discussion; G.P.-A., L.A.O. and M.C.Z. wrote the paper. Funding: This research was possible thanks to the financial support of SAI13/106 research project of Basque Country Government. 8. Appendices: Published and Submitted Works 95 Minerals 2018,8, 326 14 of 17 Acknowledgments: The authors would like to thank the anonymous referees for their comments and suggestions on the manuscript. GPA also acknowledges the PhD research grant of the Basque Country Government (2015-1-02-35). They also would like to thank Peter Smith for reviewing the use of English in the manuscript. Conflicts of Interest: The authors declare no conflict of interest. References 1. Schiffer, M. Radiocarbon Dating and the “Old Wood” Problem: The Case of the Hohokam Chronology; Elsevier: New York, NY, USA, 1986; Volume 13, pp. 13–30. 2. Mc Fadgen, B.G. Dating New Zealand archaeology by radiocarbon. N. Z. J. Sci. 1982,25, 379–392. 3. Gavin, D.G. Estimation of inbuilt age in radiocarbon ages of soil charcoal for fire history studies. Radiocarbon 2001,43, 27–44. [CrossRef] 4. Bowman, S. Radiocarbon Dating; British Museum Press: London, UK, 1990. 5. Taylor, R.; Bar-Yosef, O. Radiocarbon Dating: An Archaeological Perspective; Left Coast Press: Walnut Creek, CA, USA, 2014. 6. Boaretto, E.; Poduska, K.M. Materials science challenges in radiocarbon dating: The case of archaeological plasters. J. Mater. 2013,65, 481–488. [CrossRef] 7. Kingery, D.W.; Pamela, B.V.; Martha, P. The Beginnings of Pyrotechnology, Part II: Production and Use of Lime and Gypsum Plaster in the Pre-Pottery Neolithic Near East; Taylor and Francis: New York, NY, USA, 1988; Volume 15, pp. 219–243. 8. Labeyrie, J.; Delibrias, G. Dating of old mortar by Carbon-14 method. Nature 1964 ,201, 742–743. [CrossRef] 9. Stuiver, M.; Smith, C.S. Radiocarbon Dating of Ancient Mortar and Plaster, Proceedings of the 6th International 14 C Conference, Montreal, Canada, 8–15 September 1965; Chatters, R.M., Olson, C.A., Eds.; Clearinghouse for Federal Scientific and Technical Information: Springfield, IL, USA; pp. 338–343. 10. Pachiaudi, C.; Marechal, J.; Van Strydonck, M.; Dupas, M.; Dauchotdehon, M. Isotopic fractionation of carbon during CO2absorption by mortar. Radiocarbon 1986,28, 691–697. [CrossRef] 11. Ambers, J. Stable carbon isotope ratios and their relevance to the determination of accurate radiocarbon dates for lime mortars. J. Archaeol. Sci. 1987,14, 569–576. [CrossRef] 12. Baxter, M.S.; Walton, A. Radiocarbon dating of mortars. Nature 1970,225, 937–938. [CrossRef][PubMed] 13. Folk, R.L.; Valastro, S.J. Successful technique for dating of lime mortar by carbon-14. J. Field Archaeol. 1976 ,3, 203–208. [CrossRef] 14. Van Strydonck, M.; Dupas, M.; Dauchot-Dehon, M. Radiocarbon dating of old mortars, 14 C and Archaeology, Proceedings; Mook, W.G., Waterbolk, H.T., Eds.; PACT: Phnom Penh, Cambodia, 1983; pp. 337–343. 15. Van Strydonck, M.; Dupas, M.; Dauchotdehon, M.; Pachiaudi, C.; Marechal, J. The influence of contaminating (fossil) carbonate and the variations of delta-C-13 in mortar dating. Radiocarbon 1986 ,28, 702–710. [CrossRef] 16. Van Strydonck, M.J.Y.; Van der Borg, K.; De Jong, A.F.M.; Keppens, E. Radiocarbon dating of lime fractions and organic material from buildings. Radiocarbon 1992,34, 873–879. [CrossRef] 17. Lindroos, A.; Heinemeier, J.; Ringbom, Å.; Braskén, M.; Sveinbjörnsdóttir, Á. Mortar dating using AMS 14 C and sequential dissolution: Examples from medieval, non-hydraulic lime mortars from the Åland Islands, SW Finland. Radiocarbon 2007,49, 47–67. [CrossRef] 18. Sonninen, E.; Jungner, H. An improvement in preparation of mortar for radiocarbon dating. Radiocarbon 2001,43, 271–273. [CrossRef] 19. Hale, J.; Heinemeier, J.; Lancaster, L.; Lindroos, A.; Ringbom, Å. Dating ancient mortar. Am. Sci. 2003 ,91, 130–137. [CrossRef] 20. Nawrocka, D.; Michniewicz, J.; Pawlyta, J.; Pazdur, A. Application of radiocarbon method for dating of lime mortars. Geochronometria 2005,24, 109–115. 21. Heinemeier, J.; Jungner, H.G.; Lindroos, A.; Ringbom, S.; von Konow, T.; Rud, N. AMS 14 C dating of lime mortar. Nucl. Instrum. Methods Phys. Res. Sect. B Beam Interact. Mater. Atoms 1997,123, 487–495. [CrossRef] 22. Tubbs, L.E.; Kinder, T.N. The use of AMS for the dating of lime mortars. Nucl. Instrum. Methods Phys. Res. Sect. B Beam Interact. Mater. Atoms. 1990,52, 438. [CrossRef] 23. Toffolo, M.; Maeir, A.M.; Chadwick, J.R.; Boaretto, E. Characterization of contexts for radiocarbon dating: Results from the early Iron Age at Tell es-Safi/Gath, Israel. Radiocarbon 2012,54, 371–390. [CrossRef] Applied Mineralogy in the Study of Historical Lime Mortars 96 Minerals 2018,8, 326 15 of 17 24. Asscher, Y.; Lehmann, G.; Rosen, S.A.; Weiner, S.; Boaretto, E. Absolute dating of the late bronze to iron age transition and the appearance of philistine culture in qubur el-walaydah, southern Levant. Radiocarbon 2015 , 57, 77–97. [CrossRef] 25. Rodriguez-Navarro, C.; Hansen, E.; Ginell, W.S. Calcium hydroxide crystal evolution upon aging of lime putty. J. Am. Ceram. Soc. 1998,81, 3032–3034. [CrossRef] 26. Boynton, R.S. Chemistry and Technology of Lime and Limestone; John Wiley & Sons, Inc.: New York, NY, USA, 1980. 27. Zouridakis, N.M.; Saliege, J.F.; Person, A.; Filippakis, S.E. Radiocarbon dating of mortars from ancient greek palaces. Archaeometry 1987,29, 60–68. [CrossRef] 28. Ortega, L.A.; Zuluaga, M.C.; Alonso-Olazabal, A.; Murelaga, X.; Insausti, M.; Ibañez-Etxeberria, A. Historic lime-mortar 14 C dating of Santa María la Real (Zarautz, northern Spain): Extraction of suitable grain size for reliable 14C dating. Radiocarbon 2012,54, 23–36. [CrossRef] 29. Marzaioli, F.; Lubritto, C.; Nonni, S.; Passariello, I.; Capano, M.; Terrasi, F. Mortar radiocarbon dating: Preliminary accuracy evaluation of a novel methodology. Anal. Chem. 2011 ,83, 2038–2045. [CrossRef] [PubMed] 30. Marzaioli, F.; Nonni, S.; Passariello, I.; Capano, M.; Ricci, P.; Lubritto, C.; De Cesare, N.; Eramo, G.; Quirós Castillo, J.A.; Terrasi, F. Accelerator mass spectrometry 14 C dating of lime mortars: Methodological aspects and field study applications at CIRCE (Italy). Nucl. Instrum. Methods Phys. Res. Sect. B Beam Interact. Mater. Atoms 2013,294, 246–251. [CrossRef] 31. Folk, R.L.; Valastro, S. Successful Technique for Dating of Lime Mortar by Carbon-14. J. Field Archaeol. 1976 , 3, 203–208. [CrossRef] 32. Goslar, T.; Nawrocka, D.; Czernik, J. Foraminiferous limestone in C-14 dating of mortar. Radiocarbon 2009 ,51, 987–993. [CrossRef] 33. Heinemeier, J.; Ringbom, A.; Lindroos, A.; Sveinbjornsdottir, A.E. Successful AMS 14 C dating of non-hydraulic lime mortars from the medieval churches of the Aland Islands, Finland. Radiocarbon 2010 ,52, 171–204. [CrossRef] 34. Al-Bashaireh, K. Plaster and mortar radiocarbon dating of Nabatean and Islamic structures, South Jordan. Archaeometry 2013,55, 329–354. [CrossRef] 35. Ringbom, A.; Lindroos, A.; Heinemeier, J.; Sonck-Koota, P. 19 years of mortar dating: Learning from experience. Radiocarbon 2014,56, 619–635. [CrossRef] 36. Nonni, S.; Marzaioli, F.; Secco, M.; Passariello, I.; Capano, M.; Lubritto, C.; Mignardi, S.; Tonghini, C.; Terrasi, F. 14C mortar dating: The case of the medieval shayzar citadel, Syria. Radiocarbon 2013,55, 514–525. [CrossRef] 37. Pesce, G.; Quarta, G.; Calcagnile, L.; D’Elia, M.; Cavaciocchi, P.; Lastrico, C.; Guastella, R. Radiocarbon dating of lumps from aerial lime mortars and plasters: Methodological issues and results from San Nicolòof Capodimonte church (Camogli, Genoa, Italy). Radiocarbon 2009,51, 867–872. [CrossRef] 38. Pesce, G.L.A.; Ball, R.J.; Quarta, G.; Calcagnile, L. Identification, extraction, and preparation of reliable lime samples for 14 C dating of plasters and mortars with the “pure lime lumps” technique. Radiocarbon 2012 ,54, 933–942. [CrossRef] 39. Beruto, D.T.; Vecchiattini, R.; Giordani, M. Solid products and rate-limiting step in the thermal half decomposition of natural dolomite in a CO 2 (g) atmosphere. Thermochim. Acta 2003 ,405, 183–194. [CrossRef] 40. Schork, J. Dolomitic Lime in the US. J. Archit. Conserv. 2012,18, 7–25. [CrossRef] 41. Kuzel, H.-J.; Baier, H. Hydration of calcium aluminate cements in the presence of calcium carbonate. Eur. J. Mineral. 1996, 129–142. [CrossRef] 42. Evans, D.G.; Slade, R.C.T. Structural aspects of layered double hydroxides. In Layered Double Hydroxides; Duan, X., Evans, D.G., Eds.; Springer: Berlin/Heidelberg, Germany, 2006; pp. 1–87. 43. Forano, C.; Hibino, T.; Leroux, F.; Taviot-Guého, C. Chapter 13.1 layered double hydroxides. Dev. Clay Sci. 2006,1, 1021–1095. 44. Guo, Q.; Reardon, E.J. Calcined dolomite: Alternative to lime for minimizing undesirable element leachability from fly ash. Ind. Eng. Chem. Res. 2012,51, 9106–9116. [CrossRef] 45. Miyata, S.; Okada, A. Synthesis of hydrotalcite-like compounds and their physico-chemical properties—The systems Mg 2+ -Al 3+ -SO 42 - and Mg 2+ -Al 3+ -CrO 42 .Clays Clay Min. 1977 ,25, 14–18. [CrossRef] 8. Appendices: Published and Submitted Works 97 Minerals 2018,8, 326 16 of 17 46. Miyata, S. Physico-chemical properties of synthetic hydrotalcites in relation to composition. Clays Clay Min. 1980,28, 50–56. [CrossRef] 47. Miyata, S. Anion-exchange properties of hydrotalcite-like compounds. Clays Clay Min. 1983 ,31, 305–311. [CrossRef] 48. Reichle, W.T. Synthesis of anionic clay minerals (mixed metal hydroxides, hydrotalcite). Solid State Ionics 1986,22, 135–141. [CrossRef] 49. Cavani, F.; Trifirò, F.; Vaccari, A. Hydrotalcite type anionic clays, preparation, properties and applications. Catal. Today 1991,11, 173–301. [CrossRef] 50. Mills, S.J.; Christy, A.G.; Génin, J.-M.R.; Kameda, T.; Colombo, F. Nomenclature of the hydrotalcite supergroup: Natural layered double hydroxides. Mineral. Mag. 2012,76, 1289–1336. [CrossRef] 51. Kutus, B.; Gacsi, A.; Pallagi, A.; Palinko, I.; Peintler, G.; Sipos, P. A comprehensive study on the dominant formation of the dissolved Ca(OH) 2 (aq) in strongly alkaline solutions saturated by Ca(ii). RSC Adv. 2016 ,6, 45231–45240. [CrossRef] 52. Pallagi, A.; Tasi, A.; Gácsi, A.; Csáti, M.; Pálinkó, I.; Peintler, G.; Sipos, P. The solubility of Ca(OH) 2 in extremely concentrated NaOH solutions at 25 C. Cent. Eur. J. Chem. 2012,10, 332–337. [CrossRef] 53. Reardon, E.J.; Della Valle, S. Anion sequestering by the formation of anionic clays: Lime treatment of fly ash slurries. Environ. Sci. Technol. 1997,31, 1218–1223. [CrossRef] 54. Rosenberg, S.P.; Armstrong, L. Layered double hydroxides in the Bayer process: Past, present and future. In Essential Readings in Light Metals; Springer: Berlin, Germany, 2005; pp. 157–161. 55. Sipos, P. The structure of Al (III) in strongly alkaline aluminate solutions—A review. J. Mol. Liq. 2009 ,146, 1–14. [CrossRef] 56. Gácsi, A.; Kutus, B.; Kónya, Z.; Kukovecz, Á.; Pálinkó, I.; Sipos, P. Estimation of the solubility product of hydrocalumite-hydroxide, a layered double hydroxide with the formula of [Ca 2 Al(OH) 6 ]OH · nH 2 O. J. Phys. Chem. Solids 2016,98, 167–173. [CrossRef] 57. Artioli, G.; Secco, M.; Addis, A.; Bellotto, M. 5 Role of hydrotalcite-type layered double hydroxides in delayed pozzolanic reactions and their bearing on mortar dating. In Cementitious Materials: Composition, Properties, Application; Walter de Gruyter: Berlin, Germany, 2017. 58. Siedel, H.; Michalski, S.; Ullrich, B. Characterisation of dolomitic lime mortars from the Benedictine monastery in Riesa, Saxony (Germany). In Historic Mortars; Springer: Dordrecht, The Netherlands, 2012; pp. 115–124. 59. Brandon, C.J.; Hohlfelder, R.L.; Jackson, M.D.; Oleson, J.P. Building for Eternity: The History and Technology of Roman Concrete Engineering in the Sea; Oxbow Books: Oxford, UK; Philadelphia, PA, USA, 2014. 60. Massazza, F. Pozzolana and pozzolanic cements. In Lea’s Chemistry of Cement and Concrete, 4th ed.; Hewlett, P., Ed.; Elsevier-Butterworth-Heinemann: Oxford, UK, 1998; pp. 471–635. 61. Sagredo, I. Navarra: Castillos que Defendieron el Reino (Tomo III) La Navarra Occidental, la Frontera del Mar Álava, Bizkaia, el Duranguesado, Guipuzkoa; PAMIELA: Pamplona, Spain, 2007. 62. Solaun, J.L.; Azcárate, A. El castillo de Portilla (Zambrana, Alava). Origen y significado de una fortaleza plenomedieval en territorio alavés (siglos XI-XII). Munibe Antropol.-Arkeol. 2016,67, 167–183. 63. Ramsey, C.B.; Scott, M.; van der Plicht, H. Calibration for archaeological and environmental terrestrial samples in the time range 26–50 ka cal BP. Radiocarbon 2013,55, 2021–2027. [CrossRef] 64. Reimer, P.J.; Bard, E.; Bayliss, A.; Beck, J.W.; Blackwell, P.G.; Ramsey, C.B.; Buck, C.E.; Cheng, H.; Edwards, R.L.; Friedrich, M.; et al. IntCal13 and marine13 radiocarbon age calibration curves 0–50,000 years cal BP. Radiocarbon 2013,55, 1869–1887. [CrossRef] 65. Casadio, F.; Chiari, G.; Simon, S. Evaluation of binder/aggregate ratios in archaeological lime mortars with carbonate aggregate: A comparative assessment of chemical, mechanical and microscopic approaches. Archaeometry 2005,47, 671–689. [CrossRef] 66. Warkentin, B.P.; Maeda, T. Physical and mechanical characteristics of andisols. In Soils with Variable Charge; Theng, B.K.G., Ed.; New Zealand Society of Soil Science: Lower Hutt, New Zealand, 1980; pp. 281–302. 67. Langmuir, D. Aqueous Environmental Geochemistry; Prentice Hall: London, UK, 1997. 68. Grover, K.; Komarneni, S.; Katsuki, H. Synthetic hydrotalcite-type and hydrocalumite-type layered double hydroxides for arsenate uptake. Appl. Clay Sci. 2010,48, 631–637. [CrossRef] 69. Bakolas, A.; Biscontin, G.; Moropoulou, A.; Zendri, E. Characterization of structural byzantine mortars by thermogravimetric analysis. Thermochim. Acta 1998,321, 151–160. [CrossRef] Applied Mineralogy in the Study of Historical Lime Mortars 98 Minerals 2018,8, 326 17 of 17 70. Paama, L.; Pitkänen, I.; Rönkkömäki, H.; Perämäki, P. Thermal and infrared spectroscopic characterization of historical mortars. Thermochim. Acta 1998,320, 127–133. [CrossRef] 71. Moropoulou, A.; Bakolas, A.; Anagnostopoulou, S. Composite materials in ancient structures. Cem. Concr. Compos. 2005,27, 295–300. [CrossRef] 72. Yang, W.; Kim, Y.; Liu, P.K.T.; Sahimi, M.; Tsotsis, T.T. A study by in situ techniques of the thermal evolution of the structure of a Mg-Al-CO3layered double hydroxide. Chem. Eng. Sci. 2002,57, 2945–2953. [CrossRef] 73. León, M.; Díaz, E.; Bennici, S.; Vega, A.; Ordóñez, S.; Auroux, A. Adsorption of CO 2 on hydrotalcite-derived mixed oxides: Sorption mechanisms and consequences for adsorption irreversibility. Ind. Eng. Chem. Res. 2010,49, 3663–3671. [CrossRef] © 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). 8. Appendices: Published and Submitted Works 99 Applied Mineralogy in the Study of Historical Lime Mortars 106 Fig. 3. Location of studied samples in the Tower Keep at Irulegi Castle (modified from Ponce-Antón et al., 2019). Table 1. List of sample fractions analysed by X-ray diffraction (XRD), thermogramimetric analyses (TGA) and cathodoluminiscence (CL). Sample Code [i.e. CI-T-9B.1]: CI: Irulegi Castle, T: Tower, 9: Number of sample, B: grain-size (B: 46-75 µm grain-size window, T: 0.5-2 µm grain-size window); .1: The final number in the sample code corresponds to the number of the CO2 fraction obtained by sequential solution. Bulk mortar Bulk mortar fraction (46-75 µm) CO 2 fraction of Bulk mortar fraction Binder mortar fraction (0.5-2 µm) CO 2 fraction of Binder mortar fraction CI-T-9B CI-T-9B.1 CI-T-9T.1 CI-T-9T.2 CI-T-9 CI-T-9B.2 CI-T-9T CI-T-9B.3 CI-T-10B.1 CI-T-10T.1 CI-T-10T.2 CI-T-10 CI-T-10B CI-T-10B.2 CI-T-10T CI-T-10B.3 CI-T-13B.1 CI-T-13T.1 CI-T-13T.2 CI-T-13 CI-T-13B CI-T-13B.2 CI-T-13T CI-T-13B.3 3.2. Sample preparation In order to isolate the neoformed calcite from the mortar binder, two sample preparation procedures were performed. Both sample preparations aim to avoid contamination due to carbonated aggregates and/or unburned limestone relicts present in the mortar. One of the sample preparations was based on the settling of mortar binder and the other on the sieving of crushed mortar (Fig.4). Selected preparation products from each procedure were hydrolysed by a sequential dissolution process (Fig.5). The elementary principles of the procedures are widely described and detailed in Ortega et al. (2012b) and Ponce-Antón et al. (2018) for sample preparation by the settling process and in Lindroos et al. (2007) and Heinemeier et al. (2010) for sample preparation by the sieving process and a sequential dissolution process. Before carrying out both processes, the upper surface of all mortar samples was removed using a scraper to eliminate the organic coating of inorganic crusts formed by atmospheric exposure and avoid additional contamination problems. 8. Appendices: Published and Submitted Works 107 Fig. 4. Sample preparation procedures for mortar radiocarbon dating. (a) Sample preparation by the settling process (modified from Ponce-Antón et al., 2018). CF: coarse fraction, FF: fine fraction, UF: ultrafine fraction, TF: target fraction. Selected fraction corresponds to the 0.5-2 µm grain-size window (b) Sample preparation by the sieving process. Selected fraction corresponds to the 46-75 µm grain-size window. 3.2.1. Sample preparation procedure by a settling process Sample preparation procedure by the settling process was performed in the Clay Minerals Laboratory at the University of the Basque Country (UPV/EHU) (Leioa, Spain). The procedure is based on a particle-fractionation technique used in soil and clay mineralogical studies (Laird and Dowdy, 1994; Soukup et al., 2008). Mortar samples were first manually disaggregated to avoid mechanical crumbling, preventing the homogenization of the grain size distribution and the formation of potential contaminating small grain-size particles of carbonated aggregates (de Groot, 2004). The organic components found embedded in the mortar were picked out, removed and preserved separately. Thereafter, to improve gentle sample disaggregation the ultrasonic bath for wet samples was used preserving the original grain-size. Different grain-size fractions were extracted by differential settling of the particles in ultrapure water buffered at pH = 8 by adding pure NH4OH (Fig.4a). The 0.5-2 µm grainsize fraction of mortar binder was selected to perform sample hydrolysis by sequential dissolution for radiocarbon dating. Extraction procedure is repeated until sufficient binder is obtained for chemical-mineralogical and AMS analyses. Samples obtained by the settling preparation procedure have been named with a “T” at the end (Table 1). 3.2.2. Sample preparation procedure by a sieving process Sample preparation procedure by the sieving process was performed in the Geology and Mineralogy Laboratory at Åbo Akademi University (Turku, Finland). Mortar samples were covered with a plastic film and crushed with pliers while dry. The crushed material was sieved in a sieve series with decreasing mesh size ranging between 20 and 500 µm (Fig.4b).The 46-75 µm grain-size fraction of bulk mortar was flushed with ultrapure water and selected to perform sample hydrolysis by sequential dissolution for radiocarbon dating. Samples obtained by the settling preparation procedure have been named with a “B” at the end (Table 1). 3.2.3. Sample hydrolysis by sequential dissolution Between 38 and 44 mg of sample obtained by the settling process (0.5-2 µm grain-size window) and 80 mg of sample obtained by the sieving process (46-75 µm grain-size windows) were used for sample hydrolysis by sequential dissolution (Fig.5). Preparation products from each procedure were digested in 5 ml of 85% phosphoric acid (H3PO4) at room temperature (from 20 to 25°C). The CO2 generated by the chemical reaction was isolated in several fractions. The time of dissolution for each fraction varies until a minimum of 0.2 mg Applied Mineralogy in the Study of Historical Lime Mortars 108 of C is reached in the vial. For samples obtained by the settling process the first two successive CO2 fractions (a total of six CO2 fractions) were isolated, and for samples obtained by sieving the first three successive CO2 fractions (a total of nine CO2 fractions) were isolated. The isolated CO2 fractions were used for radiocarbon dating. Fig. 5. Preparation line for sample hydrolysis by sequential dissolution (modified from Ringbom et al., 2014). 3.3. Methods Hand sample observations were carried out by means of a Dino-Lite Premier AM7013MZT digital handheld microscope provided with a Microtouch II sensor for better observation of organic components embedded in the mortar. Magnification working distance was up to 200x and both measurements, acquisition and calibrations were carried out using DinoCapture 2.0 software. A Nikon Eclipse LV100POL microscope equipped with a DS F-11digital camera and DS L2 camera control unit was used for the petrographic studies of mortars. Mineralogical and microtextural characteristics of samples were analysed on polished thin-sections using both plane and crossed-polarized light modes. The mineralogical composition of samples was determined by means of X-ray diffraction (XRD) using a Philips X’Pert diffractometer (Malvern PANalytical, Almelo, The Netherlands) in polycrystalline powder samples. The diffractometer was provided with a monochromatic Cu-kα1 X-radiation operating at 40 kV and 20 mA. The data collection was made by a continuous scan in the range 5-70º 2θ, at an acquisition rate of 0.02° per second. Mineral phases identification was carried out with X’Pert HighScore Plus 3.0 software by PANalytical. Thermogravimetric analysis (TGA) were carried out in a TA SDT 2960 TG-DSC thermogravimetric analyser (TA Instruments, New Castle, DE, USA) by heating 10 mg of powder sample at 10°C min-1 from room temperature (from 20 to 25°C) to 900 °C under air atmosphere in a Pt crucible. Cathodoluminescence (CL) was performed in powder sample by using a Technosyn Cold Cathode unit–luminescence 8200 MK II attached to an Olympus BH–II microscope equipped with an Olympus Camedia C 7070 camera. The carbonation test was carried out for the visual assessment of the mortar carbonation degree using a phenolphthalein indicator solution (2% in ethanol). Radiocarbon dating of samples was performed by means of Accelerator Mass Spectrometry (AMS) in the Laboratory for Ion Beam Physics ETH (Zurich, Switzerland) (Synal, 2013; Synal et al., 2007) following the procedure described by Hajdas (2008). A charcoal fragment found embedded in the mortar was also dated in the Aarhus AMS Centre (AARAMS), Aarhus University (Aarhus, Denmark). Charcoal was pre-treated by the acidalkali-acid (AAA) method prior to conversion to CO2 (Bird et al., 1999). The 14C ages are 8. Appendices: Published and Submitted Works 109 reported in conventional radiocarbon years BP (Before Present = AD 1950) according to the international convention (Stuiver and Polach, 1977). Calculated 14C ages were corrected for natural isotopic fractionation based on the 14C/13C ratio measurement to be equivalent to the standard δ13C value of -25‰ VPDB. The conventional 14C ages were calibrated to calendar ages using the IntCal13 atmospheric calibration curve (Reimer et al., 2013) by means of OxCal v4.2.3 calibration software (Bronk Ramsey, 2017). The probability method was used to calculate the calibrated age ranges and will be reported at the 95.4 % confidence level (2σ). The reported δ13C values are AMS derived values. Collagen from a tooth found embedded in the mortar was extracted for radiocarbon dating using pre-cleaned ultra-filters of the Millipore Amicon Ultra-4 type with MW=30 kDa at the AARAMS (Brown et al., 1988). 4. Results and Discussion Macroscopically all mortar samples showed a heterogeneous texture with small charcoal fragments dispersed in the binder-matrix (Fig.6a). Small bone fragments (Figs. 6b and c) and an animal tooth (Fig.7) visible to the naked eye were also found in Sample CI-T-13. The tooth was identified as a lower right first or second molar (M1, M2) of a sheep/goat (J. Rofes, pers. comm., January 2019). Fig. 6. Organic fragments embedded in the Irulegi Castle lime mortars. (a) Representative charcoal fragment. (b) and (c) bone fragment from the Sample CI-T-13. Fig. 7. (a) Animal tooth embedded in the Sample CI-T-13. Images of the different faces of the tooth found embedded in the mortar binder matrix: (b) Occlusal face. (c) Apical face. (d) Buccal face. (e) Lingual face. (f) Mesial face. (g) Distal face. Applied Mineralogy in the Study of Historical Lime Mortars 110 Fig. 8. Thin section photomicrographs in cross-polarized light, XPL and plane-polarized light, PPL. The most representative textures showing the heterogeneous binder matrix-supported texture of historic lime mortars from Irulegi Castle. (a) Subangular sandstone fragment (XPL). (b) Bryozoan fragment (XPL). (c) Sandstone aggregate showing microcline crystals (XPL). (d) Microcline crystal embedded in the binder-matrix (XPL). (e) Lime lumps embedded in the binder-matrix (XPL). (f) Rounded ceramic fragment embedded in the binder-matrix (XPL). (g) Charcoal fragment (PPL). (h) Secondary calcite crystals filling cavities (XPL). Qtz: quartz, Rx: Rock fragment, Fsl: fossil; Mc: microcline, L: Lump, C: ceramic, Ch: charcoal. 8. Appendices: Published and Submitted Works 111 Thin sections of archaeological mortars were subjected to petrographic analyses under polarized-light microscopy in order to observe the overall mortar texture and to identify the binder and aggregates nature. All samples show a heterogeneous binder matrix-supported texture. All mortars are composed by a micritic calcite binder and angular to subangular quartz grains and heterometric fragments of sandstones, marls and calcarenites as aggregates (Fig. 8). Bioclast fragments (e.g. echinoderm plates, foraminifers and molluscs) and angular microcline crystals (K-feldspar) are observed scattered in the binder-matrix as a result of crushing the rocks used as aggregates, (Fig. 8a, b, c and d). Lumps < 1 mm in size, rounded ceramic fragments < 5 mm in size and charcoal fragments are also observed dispersed in the binder-matrix (Fig. 8e, f, g). The use of lime lumps for mortar radiocarbon dating (Lindroos et al., 2007; Lindroos et al., 2014; Lindroos et al., 2018; Pesce et al., 2009; Pesce et al., 2012; Van Strydonck et al., 1992) was not possible in Irulegi Castle mortars. The lime lumps were not sufficiently abundant or large enough to achieve the required amount of sample to ensure a reliable radiocarbon date. Additionally, secondary calcite crystals have been observed filling cavities, particularly in Sample CI-T-9 (Fig. 8h). Sample CI-T-13 shows scarce and small bone fragments as was also observed macroscopically (Fig. 9). Fig. 9. Thin section photomicrographs of bone fragments in Sample CI-T-13. (a) in crossed-polarized light (b) in plane polarized light. (c) on the left in crossed-polarized light and on the right in plane polarized light. Bx: bone fragment. To check sample alkalinity, the carbonation test was also carried out to assess the mortar carbonation degree visually since alkaline samples are problematic for mortar radiocarbon dating (Lichtenberger et al., 2015). According to the test results, samples were fullycarbonated since they remained colourless after reacting with the phenolphthalein, indicating a non-alkaline pH and therefore the absence of portlandite in the binder. Table 1 summarizes the sample fractions obtained both by the sieving process (46-75 µm grain-size window named with a B) and settling process (0.5-2 µm grain-size window named with a T). Carbonation test was performed in all sample fractions before analyzing them by means of X-ray diffraction (XRD), thermogravimetric analyses (TGA), cathodoluminescence analysis (CL) and AMS analysis. Calcite and quartz were the main mineral phases identified by XRD in all extracted fractions while K-feldspar and plagioclase were identified in minor amounts in samples CI-T-9B, CI-T-10B and CI-T-13B and as traces in Sample CI-T-9T (Fig. 10, Table 2). Traces of illite-like phyllosilicates were also present in Samples CI-T-9B, CI-T-10B and CI-T-13B and in minor amounts in Samples CI-T-9T, CI-T-10T and CI-T-13T. Samples in the 46-75 µm grain-size window show higher amounts of quartz, K-feldspar and plagioclase compared with samples in the 0.5-2 µm grain-size window. K-feldspars and plagioclases come from the rock fragments used as aggregates (Fig. 8c). The larger amount of these phases indicates the presence of aggregate remains in the 46-75 µm grain-size window. Aggregate remains could be attributed to the small aggregate fragments mixed with the lime Applied Mineralogy in the Study of Historical Lime Mortars 112 putty in the mixing process and to the aggregate fragments resulting from bulk mortar crushing in the sample preparation by sieving. Moreover, it should be noted that layered double hydroxide phases (LDHs) were not identified by XRD in either of the grain-size windows. LDHs have a high CO32anion capture capacity due to their ion-exchange properties that could improve the carbonation resistance of mortar (Ma et al., 2019; Miyata, 1983). Nevertheless, the identification of LDHs in samples for radiocarbon dating is essential. The high CO32affinity of LDHs makes them a potentially contaminating mineral phase group in mortar radiocarbon dating since they could incorporate CO32from the aggregates and introduce dead carbon into the system, thus ageing radiocarbon dates (Grover et al., 2010; Miyata, 1983; Ponce-Antón et al., 2018). Fig. 10. X-ray diffraction patterns of the representative samples obtained by sieving and settling processes (a) sample obtained by sieving (46-75 µm grain-size window), (b) sample obtained by settling (0.5-2 µm grain-size window). Qtz: quartz, Cal:Calcite; Plg: plagioclase, K-Fsp: potassium feldspar, Fsp: feldspars s.l., Phy: illite-like phyllosilicates. Fig. 11. Thermo-gravimetric analyses (TGA) of the different bulk mortar fractions and binder fractions obtained by sieving (46-75 µm grain-size window) and by settling (0.5-2 µm grain-size window), respectively. Thermogravimetric analyses (TGA) of studied fractions show a continuous thermogravimetric profile with four main weight losses (Fig.11). Initial weight loss takes place between room temperature (from 20 to 25°C) and 120 ºC due to the presence of adsorption water (inter-particle water) while the second weight loss between 120 ºC and 8. Appendices: Published and Submitted Works 113 200 ºC was attributed to the crystallization water (interlayer water). The third weight loss between 200 ºC and 600ºC corresponds to dehydroxylation resulting from the loss of the structural hydroxyl groups (OH-). The fourth and most important weight loss occurs at temperatures above 600 ºC when the CO2 is lost due to the carbonates decomposition (Bakolas et al., 1998; Moropoulou et al., 2005; Paama et al., 1998). Samples in the 0.5-2 µm grain-size window (CI-T-9T, CI-T-10T and CI-T-13T) show a total weight loss varying from 22% to 26.1%, while samples in the 46-75 µm grain-size window (CI-T-9B, CI-T-10B and CI-T-13B) from 25.4% to 27.1%. The presence of the phyllosilicates identified by XRD was confirmed by TGA. The weight loss in the temperature range of 400 ºC to 550 ºC in the thermogravimetric curve is associated with phyllosilicate dehydroxylation and varies with structure and composition (Cheng and Heidari, 2017; Drits and McCarty, 2007; Grim, 1962). Water-retention capacity of phyllosilicates has led to a high weight loss of the adsorption water and interlayer water varying from 7.1% to 8.7% in samples in the 0.5-2 µm grain-size window, while the weight loss in the 46-75 µm grain-size window ranges from 2.4% to 3.5%. Above 600 ºC, the weight loss related to carbonates decomposition ranges between 7.4% and 12.11% for samples in the 0.5-2 µm grain-size window and from 18.9% to 21.9% for samples in the 46-75 µm grain-size window. LDHs have not been identified by XRD because they could be under the detection limit of the analytical method. Nevertheless, the TGA confirms the absence of LDHs in all studied samples. The two continuous weight losses between 200 and 500 ºC related to OHgroups loss bonded to Al3+ and to Mg2+ corresponding to the LDHs thermal decomposition were not observed (Ficicilar and Dogu, 2006; León et al., 2010; Ma et al., 2019; Yang et al., 2002). Fig. 12. Cathodoluminescence (CL) photomicrographs of bulk mortar fractions and binder mortar fractions. (a) Sample CI-T-9B. (b) Sample CI-T-10B. (c) Sample CI-T-13B. (d) Sample CI-T-9T. (e) Sample CI-T-10T. (f) Sample CI-T-13T. Blue: quartz or K-feldspar. Greenish-yellow: plagioclase. Tile-red: binder calcite. Red-orange: carbonated aggregates of geogenic origin The CL analyses support the mineralogical composition determined by XRD and verified by TGA. Calcitic mortar binders of fractions obtained by settling and sieving show a tile-red to dark brown luminescence colour in CL (Fig. 12). Grains with a bright red-orange luminescence colour associated with carbonated aggregates of geogenic origin are observed in the 46-75 µm bulk mortar fraction samples (Fig.12a, b and c) while in the 0.5-2 µm binder fraction samples they are not observed (Fig. 12d, e and f). The blue luminescence of K-feldspar differs from the greenish-yellow colour of plagioclases (Götze et al., 2000) but blue luminescence can also be related to quartz grains. Samples CI-T-10T and CI-T-13T show Applied Mineralogy in the Study of Historical Lime Mortars 114 a scarce presence or even absence of carbonated aggregates, quartz, K-feldspar and plagioclase grains. The use of CL microscopy alone is not sufficient for mineral determination (Pagel et al., 2000). Colour observation in CL makes mineralogical interpretation difficult since differences in luminescence colours can also be a result of small variations in the composition of a mineral (Marshall, 1988). Nevertheless, CL was useful to identify the carbonated aggregate remains (bright orange luminescence) since by XRD and TGA the calcite from carbonated aggregates (geogenic calcite) cannot be differentiated from the neoformed calcite. The CL analyses show the presence of geogenic calcite in the bulk mortar fraction samples in the 46-75 µm grain-size window obtained by sieving but not in the binder fraction samples in the 0.5-2 µm grain-size window obtained by settling. The presence of geogenic calcite (carbonated aggregates) in samples in the 46-75 µm grain-size window would explain the higher carbonate content in the TGA analyses (Fig. 11). Geogenic calcite contributes to sample contamination since during sample hydrolysis it incorporates geological carbon into the system resulting in an ageing of radiocarbon dates. Table 2. Results of the mineralogical composition of bulk mortar fractions and binder mortar fractions determined by X-ray diffraction. Cal: calcite, Qz: quartz, Fsp: feldspars s.l.; Phy: illite-like phyllosilicates ****: predominant compounds; ***: high proportion; **: medium proportion; *: low proportion; tr: trace; -: undetected. Sample Mineralogy CI-T-9B CI-T-10B CI-T-13B CI-T-9T CI-T-10T CI-T-13T Size fraction 46-75 µm Size fraction 0.5-2 µm Cal *** *** *** **** **** **** Qz ** ** ** * * * Fsp * * * tr - - Phy tr tr tr * * * Bulk mortar fractions (46-75 µm grain-size window) and binder mortar fractions (0.5-2 µm) were hydrolysed and three and two CO2 fractions were obtained, respectively (Table 2, Fig. 5). Each isolated CO2 fraction was analysed by AMS for radiocarbon dating. A total of fifteen AMS 14C measurements from three mortar samples from the Tower Keep of the Irulegi Castle were performed, six from bulk mortar fractions obtained by settling and nine from mortar binder fractions obtained by sieving. Fig. 13. 14C age profiles of obtained fractions from three mortar samples from the Tower Keep at Irulegi Castle. Grey bars along the abscissas show the relative size of each CO2 increment. F: dissolution progress (scale 0 to 1 instead of 0 to 100%). The 14C age profiles are named as B-profiles for samples in the 46-75 µm grain-size window and T-profiles for samples in the 0.5-2 µm grain-size window (Fig. 13). The B-profiles show a vertical trend whereas T-profiles display a more horizontal trend. The 14C age profiles with more horizontal trends indicate less contamination in the samples 8. Appendices: Published and Submitted Works 115 (Heinemeier et al., 2010; Lindroos et al., 2007). Since the T-profiles are flatter than the B-profiles it would show that more contaminants were removed by settling than by sieving, as was observed by CL analyses (Fig. 12). Table 3 and Figure 14 show the obtained radiocarbon dating results in conventional radiocarbon ages (BP), calibrated into calendar ages (AD) and reported at the 95.4 % confidence level (2σ). Fig. 14. Calendar calibration of AMS 14C dates of bulk mortar fractions, binder mortar fractions and a charcoal fragment. In red, the military campaign of Abd Al-Rahman III in 924. In blue, the different repairs carried out in the Tower Keep and the decade of castle defence renovation. Sample code explanation in Table 1. Secondary calcite observed within the mortar could explain the rejuvenated dates (Fig. 8h). Presence of portlandite (Ca(OH)2) would indicate the alkaline nature of the sample which would react with the more recent atmospheric carbon dioxide forming secondary calcite that would yield rejuvenated radiocarbon dates. Nevertheless portlandite was not detected in the alkalinity test nor identified by XRD. Furthermore, natural meteoric water incorporates atmospheric CO2, leading to a decrease in pH and the acidification of water. Applied Mineralogy in the Study of Historical Lime Mortars 122 8. Appendices: Published and Submitted Works 123 APPENDIX II.1 Mineralogical, Textural and Physical Characterisation to Determine Deterioration Susceptibility of Irulegi Castle Lime Mortars (Navarre, Spain) Graciela Ponce-Antón, Anna Arizzi, Maria Cruz Zuluaga, Giuseppe Cultrone, Luis Angel Ortega, Juantxo Agirre Mauleon Materials 2019; 12(4):584 Applied Mineralogy in the Study of Historical Lime Mortars 124 8. Appendices: Published and Submitted Works 125 Article Metrics 9 Journal Citation Reports Citations: 3 Impact Factor 2018 5 Years 2.972 3.532 JCR® Rank Classification Quartile Percentile Materials Science Multidisciplinary 102 of 293 Q2 65.358 9 Scopus Citations: 2 CiteScore 2018 3.26 SJR 2018 0.686 SNIP 2018 1.200 CiteScore Rank Classification Percentile Materials Science (General Materials Science) 97 of 438 77 9 Google Academic Citations: 3 Applied Mineralogy in the Study of Historical Lime Mortars 126 materials Article Mineralogical, Textural and Physical Characterisation to Determine Deterioration Susceptibility of Irulegi Castle Lime Mortars (Navarre, Spain) Graciela Ponce-Antón1,* , Anna Arizzi 2, Maria Cruz Zuluaga 1, Giuseppe Cultrone 2, Luis Angel Ortega 1and Juantxo Agirre Mauleon 3 1Department of Mineralogy and Petrology, Faculty of Science and Technology, University of the Basque Country-UPV/EHU, Sarriena s/n, 48940 Leioa, Bizkaia, Spain; [email protected] (M.C.Z.); [email protected] (L.A.O.) 2Department of Mineralogy and Petrology, Faculty of Sciences, University of Granada, Avda. Fuentenueva s/n, 18002 Granada, Spain; [email protected] (A.A.); [email protected] (G.C.) 3Aranzadi Society of Sciences, Zorroagagaina 11, 20014 Donostia-San Sebastián, Gipuzkoa, Spain; [email protected] *Correspondence: [email protected]; Tel.: +34-946-015-456 Received: 29 January 2019; Accepted: 12 February 2019; Published: 15 February 2019 !"#!$%&'(! !"#$%&' Abstract: Archaeological lime mortars from the Tower Keep and West perimeter wall of Irulegi Castle (Navarre, Spain) were analysed to determine susceptibility to deterioration. Chemical, mineralogical, textural and physical characterisation was performed by different tests and multianalysis techniques in order to determine the intrinsic features of the original historical mortars at the castle. Samples from the Tower Keep are more prone to deteriorate compared with the West perimeter wall due to high water absorption capacity and high porosity. A high degree of pore interconnection, high desorption index and the presence of high pore volume in the 0.01 to 1 µ m size range affect the mortar durability since pores retain water longer inside the mortar. Local environment conditions with persistent annual rainfall, high humidity and temperature variations contribute to the decay process of the original mortar. Characterisation of historical mortars not only allows better understanding of susceptibility to deterioration but also helps the design of compatible and durable repair mortar for future interventions on historical heritage. Compatibility of new materials with the historical mortar will be ensured by studying mortar characteristics and properties. Keywords: lime mortar; mineralogy; texture; durability; deterioration; hydric behaviour; pore system 1. Introduction The preservation of built heritage requires suitable materials and techniques to enable effective restoration interventions [ 1 ]. The characterisation of original historical mortars is an important step before carrying out any repair interventions since the characteristics of the new mortar must be as similar as possible to those of the ancient mortar [ 2 ]. Differences in the material properties lead to a lack of compatibility between the new and original mortar reducing their durability [ 3 ]. Several authors have carried out chemical, mineralogical and physical analyses prior to the formulation of repair mortars [ 4 – 7 ]. Comparative studies using different limes and additives also have been carried out [ 8 – 10 ]. In addition, the material is exposed to different environmental conditions to determine how they affect the mortar properties and which factors are involved in their decay [ 11 – 15 ]. Studies of the repair material properties are performed in order to select the most suitable mortar mixture for restoration work [16]. Materials 2019,12, 584; doi:10.3390/ma12040584 www.mdpi.com/journal/materials 8. Appendices: Published and Submitted Works 127 Materials 2019,12, 584 2 of 17 Environmental factors condition material deterioration processes [ 11 , 17 ]. Water, in liquid or vapour form (e.g., as humidity), favours the irreversible phenomenon of decay, giving place to different physical, chemical and biological deterioration processes [ 18 , 19 ]. Chemical degradation of mortars takes place mainly due to hydrolysis, hydration or oxidation processes. Volume increase within the pores, by such processes as crystallization of water into ice or swelling of some clay minerals, leads to physical degradation of the material [ 20 ]. Furthermore, water can incorporate dissolved salts into the material that may crystallize after water evaporation, as well as gaseous species such as CO 2 that can dissolve the calcareous materials under specific conditions [21]. Durability of materials does not only depend on the environmental factors but also on their intrinsic mineralogical and textural features [ 22 , 23 ]. The pore system plays an important role in mortar durability since weathering processes often depend on the circulation of water inside the pores, accelerating the physical, chemical and biological deterioration [ 24 ]. Studies on hydric behaviour have been carried out to understand water deterioration mechanisms in building materials since the parameters associated with fluid uptake and transport inside the pores directly influence material deterioration [ 3 , 5 ]. Water circulation through the material is also conditioned by the presence of anisotropies and the interconnection degree between the pores [17,25]. Not only compatibility but also authenticity of the restoration material with the original mortar is one of the main goals in heritage conservation. Achieving aesthetic features in terms of visual appearance (e.g., texture and colour) is another important requirement in the restoration process [ 2 , 26 ]. Colour is a sensorial perception between the object, the lighting and the observer, so visual variations in colour between restored and original materials is an issue of interest in restoration [ 27 , 28 ]. In addition to chemical, mineralogical, physical and aesthetic characterisation, the workability is another important feature to consider in mortar formulation [26]. Irulegi Castle (Navarre, northern Spain) was built in a defensible site. Geographically the castle is located in a mid-latitude climate zone with a suboceanic west coastal maritime climate [ 29 ]. Regional climate is characterised by a moderately warm climate with cool summers and abundant rainfall well distributed throughout the year, although with two dry months. The aim of this study is to assess the hydric behaviours of lime-based archaeological mortars from Irulegi Castle in order to establish their susceptibility to deterioration. Taking into account the climatic conditions to which historical mortars are exposed, knowledge of chemical, mineralogical and physical properties will allow the formulation of an adequate repair mortar to ensure the compatibility and authenticity of the restoration material with the original mortar. 2. Archaeological Background The medieval archaeological site of Irulegi Castle is on the eastern border of the Pamplona Basin (Figure 1). It is a rock castle on Irulegi Mountain in the east of Aranguren mountain range (Navarre, Spain). The historical strategic emplacement of the castle allowed visual control of the Navarre kingdom capital and the routes to the pass over the Pyrenees along the Izagaondoa valley. The walled archaeological site is characterised by a rectangular floor 39 m ⇥ 15 m in size with an area of approximately 460 m 2 . Within the castle structures, mortars from the Tower Keep and the West perimeter wall were studied. The Tower Keep presents pseudoisodom bonding with high quality ashlars. The absence of compositional differences in the tower ashlars indicates that all the structure was built in the same construction period [ 30 ]. Nevertheless important renovations in the defensive elements of the castle were undertaken as a result of the constructive techniques developed over time. The remodelling of the Tower Keep resulted in the dismantling of the south outer wall and the original rectangular floor was transformed into the current polygonal floor with a vertex-shaped structure. This remodelling increased the floor area from 90 m 2 to 105 m 2 . The west perimeter wall shows lower-quality irregular bonding and has average dimensions of 1.25 m width and 11.35 m length (Figure 2). A continuous settlement sequence from the Late Bronze Age to the Late Middle Ages has been recognised in the archaeological site. However, the earliest fortification building is Applied Mineralogy in the Study of Historical Lime Mortars 128 Materials 2019,12, 584 3 of 17 unknown since no documentary data about the first building period of the castle exist. The oldest mentions of Irulegi Castle are dated in the second half of the 12th century and beginning of the 13th century. The castle was demolished at the end of the 15th century and currently only ruins remain standing [30,31]. Materials 2019, 12, x FOR PEER REVIEW 3 of 17 unknown since no documentary data about the first building period of the castle exist. The oldest mentions of Irulegi Castle are dated in the second half of the 12th century and beginning of the 13th century. The castle was demolished at the end of the 15th century and currently only ruins remain standing [30,31]. Figure 1. Geographic location of Irulegi Castle (Navarre, Spain). Figure 2. Location of studied samples in the Tower Keep and West perimeter wall at Irulegi Castle. 3. Materials and Methods 3.1. Materials Eight archaeological mortar samples, seven from the Tower Keep and one from the West perimeter wall at Irulegi Castle (Navarre, Spain) were collected and analysed (Table 1 and Figure 2). While the Tower Keep structure is still unconsolidated, the West perimeter wall was consolidated in 2017 but the sample corresponding to this wall was collected before the consolidation of the castle Figure 1. Geographic location of Irulegi Castle (Navarre, Spain). Materials 2019, 12, x FOR PEER REVIEW 3 of 17 unknown since no documentary data about the first building period of the castle exist. The oldest mentions of Irulegi Castle are dated in the second half of the 12th century and beginning of the 13th century. The castle was demolished at the end of the 15th century and currently only ruins remain standing [30,31]. Figure 1. Geographic location of Irulegi Castle (Navarre, Spain). Figure 2. Location of studied samples in the Tower Keep and West perimeter wall at Irulegi Castle. 3. Materials and Methods 3.1. Materials Eight archaeological mortar samples, seven from the Tower Keep and one from the West perimeter wall at Irulegi Castle (Navarre, Spain) were collected and analysed (Table 1 and Figure 2). While the Tower Keep structure is still unconsolidated, the West perimeter wall was consolidated in 2017 but the sample corresponding to this wall was collected before the consolidation of the castle Figure 2. Location of studied samples in the Tower Keep and West perimeter wall at Irulegi Castle. 3. Materials and Methods 3.1. Materials Eight archaeological mortar samples, seven from the Tower Keep and one from the West perimeter wall at Irulegi Castle (Navarre, Spain) were collected and analysed (Table 1and Figure 2). While the Tower Keep structure is still unconsolidated, the West perimeter wall was consolidated in 2017 but the sample corresponding to this wall was collected before the consolidation of the castle 8. Appendices: Published and Submitted Works 129 Materials 2019,12, 584 4 of 17 ruins. Considering the studied mortars correspond to archaeological materials, sample selection was determined on the basis of the minimum volume required to perform the capillary tests. Table 1. Studied samples from different structures at Irulegi Castle. Archaeological Structure Sample West perimeter wall CI-M-3 Tower Keep CI-T-8 CI-T-9 CI-T-10 CI-T-11 CI-T-12 Tower Keep extension CI-TE-8 CI-TE-9 3.2. Methods Different analytical techniques and tests were performed to determine the mineralogy, chemistry, texture and physical properties of the collected archaeological mortars. 3.2.1. Mineralogical, Chemical and Petrographic Characterisation The mineralogical composition of samples was determined by means of X-ray diffraction (XRD) using a Philips X’Pert diffractometer (Leioa, Spain) equipped with a monocromatic Cu-k ↵1 X-radiation operating at 40 kV and 20 mA. The data collection on the powder sample was performed by a continuous scan in the range from 5 to 70  2 ✓ , at an acquisition rate of 0.02  per second. Mineral phase identifications were performed with X’Pert HighScore Plus 3.0 software by PANalytical (Leioa, Spain). Chemical composition of major elements in bulk mortar was established by means of X-ray Fluorescence (XRF) in powder sample. Measurements were taken by Wavelength Dispersive X-ray Fluorescence (WDXRF) using a PANalytical Axios Advanced PW4400 XRF spectrometer (4 kW Rh anode SST-mAX X-ray tube, Leioa, Spain). Fused beads were obtained after heating a sample and lithium borate flux (Spectromelt A12, Merck, Leioa, Spain) mixture in approximate 20:1 proportions at ~1200  C for 3 min in Pt/Au crucibles using a PANalytical Perl’X3 fusion machine. Detection lower limits for major elements are in the range of 0.01 wt %. The loss on ignition (LOI) has been calculated after heating a powder sample of bulk mortar at 1050 C for one hour. The mortar texture and nature of components were determined in polished thin sections using a Nikon Eclipse LV100POL microscope (Leioa, Spain) equipped with DS F-I1 digital camera and a DS L-2 control unit. 3.2.2. Characterisation of Pore System and Hydric Behaviour Mercury intrusion porosimetry (MIP) was used to determine the pore size distribution and the open porosity (P MIP ) by a Poremaster-60 GT (Quantachrome Instruments, Alicante, Spain), with a maximum injection pressure of 414 MPa, measuring the pore diameter range from approximately 0.003 to 360 µ m. Mortar sample fragments about 1 cm 3 were oven-dried for 24 h at 60  C before the analysis. To obtain a complete vision of the pore system, hydric tests (HT) were carried out in samples of 3 cm 3 in size; previously oven-dried at 80  C for 24 h. Measurements were taken under controlled thermo-hygrometric conditions at 25  C and 50% relative humidity. The test measurements were performed on no more than two or three samples per mortar type, since samples are archaeological materials. The free (A b ) and forced (A f , under vacuum) water absorption values and absorption coefficient (C a ) were determined following the UNE-EN 13755 [ 32 ] standard. The degree of interconnection Applied Mineralogy in the Study of Historical Lime Mortars 130 Materials 2019,12, 584 5 of 17 between the pores (A x )[ 33 ] and the saturation coefficient (S) [ 34 ] were also determined. These hydric parameters were calculated as follows Ab=MLM0 M0·100 (1) where M0is the mass of the dried sample and MLis the mass of the sample saturated under water at atmospheric pressure (until constant mass is reached): Af=MsM0 M0·100 (2) Ax=AfAb Af·100 (3) Ca=Ab pt(4) where M S is the mass of the sample saturated with water under vacuum. The absorption coefficient (C a ) is determined as the slope of the curve representing the weight increase as a function of the square root of time 4 min after the beginning of the test: S=M48h M0 MSM0·100, (5) where M48h is the mass of the sample after 48 h immersion in water at atmospheric pressure. Drying index (D i ) is defined as the definite integral of the drying curve from the beginning (t 0 ) to the end (t f ) times of the test in which M t represents a decreasing water weight content starting from the saturation values (under vacuum) as a function of time. The D i was measured according to the NORMAL 29/88 [35]: Di=Rtf t0f(Mt)dt MS·tf(6) The capillarity coefficient (C c ) and the capillarity height (H c ) of samples were calculated according to the UNE-EN 1925 [36] standard: Cc=MtM0 A·pt, (7) where M t is the amount of water absorbed at time t and A is the surface of the sample in contact with the water: Hc=h pt(8) where h is the height of water rise by capillarity at time t. Finally, UNE-EN 1936 [ 37 ] standard was used to determine the open porosity (P HT ) and skeletal (⇢Hsk) and bulk (⇢Hb) densities as follows PHT =MsM0 MsMH·100 (9) ⇢Hsk =M0 M0MH(10) ⇢Hb =M0 MsMH, (11) where MHis the mass of the sample saturated with water under vacuum and weighted in water. 8. Appendices: Published and Submitted Works 131 Materials 2019,12, 584 12 of 17 Materials 2019, 12, x FOR PEER REVIEW 12 of 17 Figure 6. Hydric behaviours of Irulegi Castle lime mortars. (a) Free water absorption, forced water absorption and drying curves. Weight variation (ΔM/M) versus time (in hours). (b) Capillary uptake curves: Weight variation (ΔM/S) versus time (in hours) and (c) capillarity front curves. Height (in mm) versus time (in hours). Regarding capillary uptake curves, samples absorb water quickly at the beginning of the test and as samples become saturated in water the velocity of capillary rise decreases and stabilizes reaching an equilibrium value (Figure 6b), following the most common capillary rise trend found for lime mortars [5]. The nonlineal curves showing two sections with different slopes are due to the presence of two main families of pores in the mortars [48] as MIP analysis revealed (0.01 µm < r < 1 Figure 6. Hydric behaviours of Irulegi Castle lime mortars. ( a ) Free water absorption, forced water absorption and drying curves. Weight variation ( D M/M) versus time (in hours). ( b ) Capillary uptake curves: Weight variation ( D M/S) versus time (in hours) and ( c ) capillarity front curves. Height (in mm) versus time (in hours). Regarding capillary uptake curves, samples absorb water quickly at the beginning of the test and as samples become saturated in water the velocity of capillary rise decreases and stabilizes reaching an equilibrium value (Figure 6b), following the most common capillary rise trend found for lime Applied Mineralogy in the Study of Historical Lime Mortars 138 Materials 2019,12, 584 13 of 17 mortars [ 5 ]. The nonlineal curves showing two sections with different slopes are due to the presence of two main families of pores in the mortars [ 48 ] as MIP analysis revealed (0.01 µ m<r<1 µ m and 1 µ m<r<10 µ m). Samples CI-T-10 and CI-TE-8 have high capillarity coefficient (C C ) values because they absorb water faster than samples CI-M-3 and CI-TE-9, which indeed show lower C C values (Table 4). The capillary front reached the top of all samples after 48 h except in Sample CI-TE-9 where water did not reach the top until 216 h (nine days) after the beginning of the test (Figure 6c). However, this visual saturation does not coincide in time with the real saturation that occurs after 400 h ( ~16 days ) (Figure 6b,c). This delay confirms the presence of two families of pores, which are filled at different velocities by water (smaller pores are filled first). Saturation is achieved when all connected pores are filled. Samples CI-M-3 and CI-T-11 show the highest values of both bulk ( ⇢Hb ) and skeletal ( ⇢Hsk ) density (Table 4). Differences between skeletal and bulk densities are related to the porosity of mortars. This difference is greater in the more porous samples (CI-T-9, CI-T-10, CI-TE-8 and CI-TE-9). 4.3. Nondestructive Tests Table 5summarizes the ultrasound measurements in mortar samples. Considering lime mortar as an ideal two-phase media of aggregate embedded in a calcitic matrix, V p values depend on the wave velocity both in the matrix and the aggregates, since ultrasonic wave propagation is different in each phase. The V p decreases considerably when the wave propagates from an aggregate to the matrix [ 49 ]. No relationship between the V p and aggregate size has not been found probably because aggregates act as a homogeneous structure considering size a constant parameter [ 50 ]. However, aggregate mineralogy is important in ultrasonic wave propagation velocity [51]. In fact, waves propagate more quickly through calcite (approximately 6660 m/s) than through quartz (approximately 5800 m/s) [ 52 ]. Therefore, P-wave velocity is directly related to the petrographic characteristic of the mortar. V p values decrease in all mortar samples due to the presence of a large amount of siliceous aggregates, except in Sample CI-M-3, which contains the lowest amount of aggregates. Porosity also affects the ultrasonic wave propagation velocity since when the wave propagates from a solid (aggregates or matrix) through a gaseous medium (pores) the ultrasonic wave propagation velocity decreases [ 15 ]. Ultrasound data, indeed, are in agreement with the above-mentioned porosity results (Tables 4and 5). The presence of small cracks also affects V p , causing a fall in velocity [ 53 ], as in samples CI-T-11, CI-T-12, CI-TE-8 and CI-TE-9. Table 5. Results of ultrasonic wave propagation through lime mortars from Irulegi Castle. V P1 ,V P2 and V P3 (in m/s): P-wave velocity in three orthogonal directions; D M p : total anisotropy coefficient of P-waves. CI-M-3 CI-T-8 CI-T-9 CI-T-10 CI-T-11 CI-T-12 CI-TE-8 CI-TE-9 VP1 1815.48 186.75 178.77 130.80 158.19 150.49 178.77 151.83 VP2 1828.91 197.60 340.66 134.20 159.79 169.49 191.62 183.43 VP3 1820.90 197.60 358.70 132.78 197.37 157.36 203.82 177.51 DM 0.52 5.49 48.88 2.01 11.43 7.92 9.58 15.87 The total anisotropy coefficient of P-waves ( D M p ) confirms the textural homogeneity of CI-M-3 sample and the textural heterogeneity of the rest of the samples. Sample CI-M-3 gave the lowest D M p value and sample CI-T-9 the highest (Table 5). The chromatic parameters of each mortar are summarised in Table 6. Colorimetric analyses showed that the lightness value (L*) was lower for samples CI-M-3, CI-T-9, CI-T-10 and CI-T-11, while samples CI-T-12, CI-TE-8 and CI-TE-9 show the higher L* values. The chromatic axes (a* and b*) values tend towards to the light grey field due to a luminosity value close to 80. The a* values are very similar in all samples except for Sample CI-M-3 which presents the highest values. Samples CI-T-12 8. Appendices: Published and Submitted Works 139 Materials 2019,12, 584 14 of 17 and CI-TE-9 have the lowest b* values. Lower L* is due to the presence of aggregates, phyllosilicate phases and iron oxides, as petrographic and XRD analyses indicate. Table 6. Chromatic parameters of mortar samples. Lightness (L*), chromatic coordinates (a* and b*), chroma (C*), hue angle (H). CI-M-3 CI-T-8 CI-T-9 CI-T-10 CI-T-11 CI-T-12 CI-TE-8 CI-TE-9 L* 72.31 78.31 76.76 73.69 73.41 80.79 80.55 80.24 a* 3.22 2.36 2.35 2.95 2.38 2.15 2.81 2.04 b* 13.79 11.83 11.26 14.67 12.8 9.63 12.86 9.76 C* 14.16 12.07 11.51 14.96 13.02 9.86 13.17 9.97 H 76.85 78.71 78.06 78.63 79.46 77.45 77.82 78.22 According to the measured parameters, samples CI-T-9, CI-T-10, CI-TE-8 and CI-TE-9 (South-Southeast face of the Tower Keep) present the highest free water absorption values ( Ab> 25% ), high porosity values (P HT and P MIP > 40%) with good pore interconnection (lowest A x values), favouring the incorporation of dissolved salts and gaseous species such as CO 2 into the material that could deteriorate the mortar. Samples CI-T-11 and CI-T-12 (Southwest wall of the Tower Keep) display the worst pore interconnection (higher A x values) and dry more slowly (higher D i values), indicating a longer water retention also affecting mortar durability. Only sample CI-M-3 from the West perimeter wall shows less potential of deterioration due to the low free water absorption values (A b < 19%), fast drying and lower porosity (PHT and PMIP ~32%). Additionally, environmental factors condition mortar durability due to the presence of water both as humidity (water vapour) and as rainfall (liquid water). The climatic conditions at Irulegi Castle favour mortar deterioration since the average annual precipitation is around 858 mm and in 10 months rainfall is above 50 mm. The annual average humidity is ~76% but in summer periods the humidity is higher than the average values. Moreover, the average temperature is 11.8  C but the absolute average minimum and maximum temperatures are  12.4  C and 39.9  C, respectively [ 54 ]. The wide variation between absolute maximum and minimum temperature together with the high humidity favour the physical weathering of mortars. Material exposure to temperature variations leads to thermal expansion and temperatures below freezing result in frost wedging causing cracking of mortars. Additionally, the persistent rainfall favours dissolved salts and CO 2 incorporation into the mortars producing crystal growth and carbonate species dissolution, respectively. 5. Conclusions and Perspectives The mineralogical, chemical and physical properties of eight archaeological lime mortar samples from Irulegi Castle were determined to enable an understanding of their susceptibility to deterioration. High pore volume in the 0.01 to 1 µ m size range is one of the reasons for the durability problems that the studied mortars might suffer in the future, since smaller pores retain water longer and dry more slowly. Related with their pore system, samples from the Tower Keep show high susceptibility to deterioration compared with the West perimeter wall sample. Samples from the south-southeast face of the Tower Keep show higher water absorption capacity and porosity (with good pore interconnection), while samples from the Southwest wall present the worst pore interconnection and dry more slowly. Not only do the intrinsic features of the original mortars of Irulegi Castle, but also the local environmental exposure conditions, affect mortar deterioration. The persistent rainfall during the year, high humidity and temperature variations in this area certainly contribute to weathering processes in the original mortars. To design durable and compatible repair material for this castle, original mortar characteristics and environmental conditions should be taken into account. Considering that the studied mortars are archaeological medieval mortars, differences in the physical properties among nearby samples would not necessarily indicate different mortar Applied Mineralogy in the Study of Historical Lime Mortars 140 Materials 2019,12, 584 15 of 17 manufacturing processes but could instead correspond to the typical heterogeneity of this type of material. This study was able to determine the chemical-mineralogical characteristics and physical properties of the original historical mortars at Irulegi Castle, with positive implications for the design of compatible and durable repair mortar in future interventions. It will be essential to select the most appropriate mortar composition to ensure a satisfactory and long-lasting repair intervention. Compatibility, durability, authenticity and reversibility of the repair materials are indeed crucial requirements in any restoration work to be carried out in the future in this castle. In the future, additional decay tests, including salt crystallization, wet and dry cycles, rainfall exposure and freeze-thaw cycles, should be carried out to assess the deterioration processes due to environmental agents in the area. Author Contributions: Conceptualization, G.P.-A., A.A., G.C., M.C.Z. and L.A.O.; Data Curation, G.P.-A.; Writing-Original Draft Preparation, G.P.-A.; Writing—Review & Editing, G.P.-A., M.C.Z., A.A. and G.C.; Funding Acquisition, A.A., G.C., L.A.O. and J.A.M. All authors read and approved the final manuscript. Funding: This study was possible thanks to the financial support of Junta de Andalucía Research Group RNM179 and Research Project MAT2016-75889-R. Acknowledgments: G.P.-A. acknowledges the PhD research grant of the Basque Government [2015-1-02-35]. The authors would like to thank Peter Smith for reviewing the use of English in the manuscript. Conflicts of Interest: The authors declare no conflicts of interest. References 1. ICOMOS Declaration of Amsterdam-1975. Available online: https://www.icomos.org/en/and/169-thedeclaration-of-amsterdam (accessed on 14 February 2019). 2. Schueremans, L.; Cizer, Ö.; Janssens, E.; Serré, G.; Balen, K.V. Characterization of repair mortars for the assessment of their compatibility in restoration projects: Research and practice. Constr. Build. Mater. 2011 ,25, 4338–4350. [CrossRef] 3. Groot, C.; Ashall, G.J.; Hughes, J.J.; Bartos, P.J. Characterisation of old mortars with respect to their repair: A state of the art. Rilem Rep. 2007,28, 1. 4. Hughes, J.J.; Cuthbert, S.J. The petrography and microstructure of medieval lime mortars from the west of Scotland: Implications for the formulation of repair and replacement mortars. Mater. Struct. 2000 ,33, 594–600. [CrossRef] 5. Arizzi, A.; Cultrone, G. The water transfer properties and drying shrinkage of aerial lime-based mortars: An assessment of their quality as repair rendering materials. Environ. Earth Sci. 2014 ,71, 1699–1710. [CrossRef] 6. Morillas, H.; Vazquez, P.; Maguregui, M.; Marcaida, I.; Silva, L.F.O. Composition and porosity study of original and restoration materials included in a coastal historical construction. Constr. Build. Mater. 2018 , 178, 384–392. [CrossRef] 7. Nogueira, R.; Ferreira Pinto, A.P.; Gomes, A. Design and behavior of traditional lime-based plasters and renders. Review and critical appraisal of strengths and weaknesses. Cem. Concr. Compos. 2018 ,89, 192–204. [CrossRef] 8. Arizzi, A.; Cultrone, G. The difference in behaviour between calcitic and dolomitic lime mortars set under dry conditions: The relationship between textural and physical–mechanical properties. Cem. Concr. Res. 2012,42, 818–826. [CrossRef] 9. Arizzi, A.; Cultrone, G. Aerial lime-based mortars blended with a pozzolanic additive and different admixtures: A mineralogical, textural and physical-mechanical study. Constr. Build. Mater. 2012 ,31, 135–143. [CrossRef] 10. Silva, B.A.; Ferreira Pinto, A.P.; Gomes, A. Natural hydraulic lime versus cement for blended lime mortars for restoration works. Constr. Build. Mater. 2015,94, 346–360. [CrossRef] 11. Charola, A.; Kwiatkowski, D.; Löfvendahl, R. Stone deterioration in historic buildings and monuments. In Proceedings of the 10th International Congress on Deterioration and Conservation of Stone, Stockholm, Sweden, 27 June–2 July 2004. 8. Appendices: Published and Submitted Works 141 Materials 2019,12, 584 16 of 17 12. Cultrone, G.; Sebastian, E. Laboratory simulation showing the influence of salt efflorescence on the weathering of composite building materials. Environ. Geol. 2008,56, 729–740. [CrossRef] 13. Izaguirre, A.; Lanas, J.; Álvarez, J.I. Ageing of lime mortars with admixtures: Durability and strength assessment. Cem. Concr. Res. 2010,40, 1081–1095. [CrossRef] 14. Arizzi, A.; Viles, H.; Cultrone, G. Experimental testing of the durability of lime-based mortars used for rendering historic buildings. Constr. Build. Mater. 2012,28, 807–818. [CrossRef] 15. Arizzi, A.; Huerga, G.M.; Sebastián, E.; Cultrone, G. Mineralogical, textural and physical-mechanical study of hydraulic lime mortars cured under different moisture conditions. Mater. Construcc. 2015.[CrossRef] 16. Lanas, J.; Alvarez-Galindo, J.I. Masonry repair lime-based mortars: factors affecting the mechanical behavior. Cem. Concr. Res. 2003,33, 1867–1876. [CrossRef] 17. Charola, A.E.; Lanzzarini, L. Material Degradation Caused by Acid Rain. In ACS Symposium; Baboian, R., Ed.; American Chemical Society: Washington, DC, USA, 1986; pp. 250–258. 18. Kühnel, R.A. Driving forces of rock degradation. In Protection and Conservation of the Cultural Heritage of the Mediterranean Cities; Galan, E., Zezza, F., Eds.; Swets & Zeitlinger: Lisse, The Netherlands, 2002; pp. 11–17. 19. Veniale, F.; Setti, M.; Lodola, S. Diagnosing stone decay in built heritage. Facts and perspectives. Mater. Construcc. 2008,58, 11–32. [CrossRef] 20. Esbert, R.; Montoro, M.; Ordaz, J. Rock as a construction material durability deterioration and conservation. Mater. Construcc. 1991,41, 61–73. [CrossRef] 21. Winkler, E.M. Weathering and weathering rates of natural stone. Environ. Geol. Water Sci. 1987 ,9, 85–92. [CrossRef] 22. Ordóñez, S.; Fort, R.; Del Cura, M.G. Pore size distribution and the durability of a porous limestone. Q. J. Eng. Geol. Hydrogeol. 1997,30, 221–230. [CrossRef] 23. Török, Á.; Vásárhelyi, B. The influence of fabric and water content on selected rock mechanical parameters of travertine, examples from Hungary. Eng. Geol. 2010,115, 237–245. [CrossRef] 24. Molina, E.; Cultrone, G.; Sebastián, E.; Alonso, F.J.; Carrizo, L.; Gisbert, J.; Buj, O. The pore system of sedimentary rocks as a key factor in the durability of building materials. Eng. Geol. 2011 ,118, 110–121. [CrossRef] 25. Hall, C.; Hoff, W.D. Water Transport in Brick, Stone and Concrete; Taylor & Francis: London, UK, 2002. 26. Van Balen, K.; Hendrickx, R. Preservation of workmanship or workmanship for preservation. In Proceedings of the 6th International Conference on Structural Analysis of Historical Constructions: Preserving Safety and Significance, Bath, UK, 2–4 July 2008; pp. 3–12. 27. Lozano, R.D. El Color y su Medición: Con Una Introducción a la Óptica Fisiológica y al Estudio de la Visión; Américalee S.R.L.: Buenos Aires, Argentina, 1978. 28. López, A.; Guzmán, G.A.; Di Sarli, A.R. Color stability in mortars and concretes. Part 1: Study on architectural mortars. Constr. Build. Mater. 2016,120, 617–622. [CrossRef] 29. Peel, M.C.; Finlayson, B.L.; McMahon, T.A. Updated world map of the Köppen-Geiger climate classification. Hydrol. Earth Syst. Sci. 2007,11, 1633–1644. [CrossRef] 30. Buces Cabello, J.; Moraza Barea, A.; Agirre Mauleon, J.; Pescador Medrano, A.; Legorburu Arzamendi, M. Un enclave estratégico en la Cuenca de Pamplona: el castillo medieval de Irulegi (Lakidain, Navarra). Balance de los trabajos arqueológicos (2007–2012). Available online: http://www.aranzadi.eus/wp-content/ files_mf/1390899077Irulegi.pdf (accessed on 14 February 2019). 31. Martinena Ruiz, J.J. Navarra Castillos y Palacios; Caja de Ahorros de Navarra: Pamplona, Spain, 1980. 32. UNE-EN 13755, Natural Stone Test Methods Determination of Water Absorption at Atmospheric Pressure; AENOR: Madrid, Spain, 2008. 33. Cultrone, G.; De La Torre, M.J.; Sebastián, E.; Cazalla, O. Evaluation of bricks durability using destructive and nondestructive methods (DT and NDT). Mater. Construcc. 2003,53, 41–59. [CrossRef] 34. RILEM. Recommended test to measure the deterioration of stone and to assess the differences of treatment methods. Mater. Struct. 1980,13, 175–253. [CrossRef] 35. NORMAL 29/88, Misura Dell’indice di Asciugamento (Drying Index); CNR-ICR: Rome, Italy, 1988. 36. UNE-EN 1925, Natural Stone Test Methods. Determination of Water Absorptioncoefficient by Capillarity; AENOR: Madrid, Spain, 2000. 37. UNE-EN 1936, Natural Stone Test Methods. Determination of Real Density and Apparent Density, and of Total and Open Porosity; AENOR: Madrid, Spain, 2007. Applied Mineralogy in the Study of Historical Lime Mortars 142 Materials 2019,12, 584 17 of 17 38. ASTM D 2845-05, Standard Method for Laboratory Determination of Pulse Velocities and Ultrasonic Elastic Constants of Rock; ASTM International Standards Worldwide: West Conshohocken, PA, USA, 2005. 39. Guyader, J.; Denis, A. Wave propagation in anisotropic rocks under stress evaluation of the quality of slates. Bull. Int. Assoc. Eng. Geol. 1986,33, 49–55. [CrossRef] 40. UNE-EN 15886, Conservation of Cultural Property. Test Methods. Colour Measurement of Surfaces; AENOR: Madrid, Spain, 2011. 41. Valdeón, L.; Esbert, R.M.; Grossi, C.M. Hydric properties of some Spanish building stones: a petrophysical interpretation. Mater. Issues Art Archaeol. 1993,3, 911–916. [CrossRef] 42. Alejandre Sánchez, F.J. Historia, Caracterización y Restauración de Morteros; Universidad de Sevilla: Sevilla, Spain, 2002. 43. Benavente, D. Why pore size is important in the deterioration of porous stones used in the built heritage. Macla 2011,15, 41–42. 44. Scherer, G.W. Theory of Drying. J. Am. Ceram. Soc. 1990,73, 3–14. [CrossRef] 45. Rodriguez-Navarro, C. Técnicas de análisis del sistema poroso de un material pétreo ornamental. In Cuadernos Tecnicos "Tecnicas de Diagnostico Aplicadas a la Conservacion de los Materiales de Construccion en los Edificios Historicos"; Instituto Andaluz del Patrimonio Histórico: Sevilla, Spain, 1996; Volume 2, pp. 51–65. 46. Cultrone, G.; Madkour, F. Evaluation of the effectiveness of treatment products in improving the quality of ceramics used in new and historical buildings. J. Cult. Herit. 2013,14, 304–310. [CrossRef] 47. Kirk, R.E.; Othmer, D.F. Encyclopedia of Chemical Technology; Wiley: New York, NY, USA, 2004. 48. Beck, K.; Al-Mukhtar, M.; Rozenbaum, O.; Rautureau, M. Characterization, water transfer properties and deterioration in tuffeau: building material in the Loire valley-France. Build. Environ. 2003 ,38, 1151–1162. [CrossRef] 49. Arizzi, A.; Martínez-Martínez, J.; Cultrone, G. Ultrasonic wave propagation through lime mortars: An alternative and non-destructive tool for textural characterization. Mater. Struct. 2013 ,46, 1321–1335. [CrossRef] 50. Philippidis, T.P.; Aggelis, D.G. Experimental study of wave dispersion and attenuation in concrete. Ultrasonics 2005,43, 584–595. [CrossRef][PubMed] 51. Schön, J.H. Physical Properties of Rocks: Fundamentals and Principles of Petrophysics; Pergamon: Oxford, UK, 1996. 52. Carmichael, R.S. Practical Handbook of Physical Properties of Rocks and Minerals; CRC press: Boca Raton, FL, USA, 1989. 53. Molina, E.; Benavente, D.; Sebastian, E.; Cultrone, G. The influence of rock fabric in the durability of two sandstones used in the Andalusian Architectural Heritage (Montoro and Ronda, Spain). Eng. Geol. 2015 ,197, 67–81. [CrossRef] 54. Beortegi GN. Available online: http://meteo.navarra.es/climatologia/selfichaclima.cfm?IDEstacion=12& tipo=AUTO (accessed on 17 January 2019). © 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). 8. Appendices: Published and Submitted Works 143 Applied Mineralogy in the Study of Historical Lime Mortars 144 8. Appendices: Published and Submitted Works 145 APPENDIX II.2 Lime mortars from Amaiur Castle (Navarre, Spain): mineralogical and physical characterization to assess their durability Graciela Ponce-Antón, Anna Arizzi, Maria Cruz Zuluaga, Giuseppe Cultrone, Luis Angel Ortega, Juantxo Agirre Mauleon Submitted to Construction and Building Materials Applied Mineralogy in the Study of Historical Lime Mortars 146 8. Appendices: Published and Submitted Works 147 Lime mortars from Amaiur Castle (Navarre, Spain): mineralogical and physical characterization to assess their durability Abstract: Mineralogical, chemical and physical characterizations were performed on the archaeological lime mortars from different structures at Amaiur Castle (Navarre, Spain) in order to determine their durability. Samples from the south-east of the filling mortar and 16th century bastion and the samples from the south-east of the 17th century bastion may decay more easily. The high porosity and water absorption capacity, the poor interconnection of pores and the difficulty for drying are the main factors involved in their deterioration. A south-east sample from the 16th century bastion was also susceptible to deterioration and could be related to the repairs performed during the 16th century as described in written sources. Water absorption capacity of mortars from the cistern could affect the preservation of the remains of the cistern vault. Mineralogical characterization allowed an approach to the technological knowledge used in the mortar manufacturing process at Amaiur Castle. Hydrotalcite and hydromagnesite identified in the mortar binder support the use of the traditional hot-mixing method in the mortar manufacture. The hot-mixing method would be advantageous in the damp and cold climate conditions prevailing in the region where Amaiur Castle is located. Keywords: lime mortar; deterioration; hydric behaviour; hydromagnesite; hydrotalcite; hotmixed mortar 1. Introduction Knowledge of the composition and behaviour of historical mortars has improved since the first studies at the end of the 19th century [1]. Chemical and mineralogical characterizations of these materials have been increasing since the approval of the Venice Charter in 1964 [2] and the foundation of the International Council on Monuments and Sites (ICOMOS) in 1975. Mineralogical, chemical and physical characterization of historical mortars is essential to assess compatibility between the original and repair mortars in restoration projects [3, 4] and thus ensure architectural heritage conservation [5]. Knowledge of the hydric behaviour of porous materials such as mortars is essential to assess their durability over time. Water is one of the most harmful agents and its flow through a porous system plays an important role in building material deterioration [6, 7]. Furthermore, the climate conditions not only influence the mortar hardening process but also conditioned the water presence in the mortar affecting the mortar durability [8, 9]. Mineralogical, chemical and physical characterization and hydric behaviour studies have been performed to evaluate the durability of historical mortars and/or to ensure the quality of repair mortars used in the historical buildings [10-14]. Previous studies point to the use of the traditional hot-mixing method in the mortar manufacture at Amaiur Castle (Navarre Spain) [15]. The combination of chemicalmineralogical analyses and physical properties in the study of historical mortars are useful to investigate the traditional hot-mixing method and the different building phases of different periods at the castle. The present study aims to characterize mineralogical, chemical and physical features of historical lime mortars from Amaiur Castle to assess their durability. The study of the pore Applied Mineralogy in the Study of Historical Lime Mortars 154 Fig. 4. Photomicrographs of the most representative microtextural features of the lime mortars from Amaiur Castle. (a) Heterogeneous binder matrix-supported texture with angular to subangular dolostone fragments embedded in a micritic calcite matrix. (b) Mortar with a subrounded ceramic fragment. (c) Sandstone aggregate in a mortar with high porosity. (d) Large dolostone aggregate in a mortar with low porosity. (e) Mortar with a lime lump. (f) Mortar with Mg-rich spots and hydromagnesite crystals. (g) Hydromagnesite crystals filling the binder pores and dolostone vuggy pores. (h) Microcracks with secondary calcite inside. Reaction zone in the dolomitic aggregates is shown in all photomicrographs. B: binder. C: ceramic fragment. SCal: secondary calcite. Ck: microcrack. DRx: dolostone. HMgs: hydromagnesite. L: lime lump. Mg-SP: Mg-rich spot. P: pore. Qz: quartz. R: reaction zone. SRx: sandstone. VP: vuggy porosity. 8. Appendices: Published and Submitted Works 155 4.4. Characterization of Pore System and Hydric Behaviour Mortars show a complex pore system since they are composed of both porous binder and different porous aggregates [45]. Water constitutes an important degradation agent for building materials since its circulation and retention within the porous materials causes their deterioration and in some cases irreversible damage. Therefore, mortar characterization through the porous system is essential since the porosity and pore size distribution affect the water circulation within the material [46, 47]. Mercury intrusion porosimetry (MIP) was used to evaluate the pore size distribution of the mortars. Table 4 summarises the obtained MIP values. The highest porosity values (PMIP) were measured in Samples CA-B1-4 and CA-B2-3 (45% and 37.8%, respectively), whereas the lowest value were measured in Sample CA-R-8 and Sample CA-B1-13 (26.3% and 27.7%, respectively). Table 4. Hydric parameters and porosity values of the lime mortars from Amaiur Castle. Ab: Free water absorption (%). Af: forced water absorption (%). Ax: degree of pore interconnection (%). S: Saturation coefficient (%). Ca: absorption coefficient (g/min0.5). Di: drying index. ρHb: bulk density (g/cm3). ρHsk: skeletal density (g/cm3). Cc: capillarity coefficient (g/cm2 min0.5). Hc: Height of the water level during capillary uptake (mm s−0.5). PHT and PMIP: open porosity (%) determined by hydric tests (HT) and mercury intrusion porosimetry (MIP), respectively. Regarding the pore size distribution (Fig.5), all samples show a family of small pores of 0.01 < r < 1 µm connected to a family of large pores of 1 < r < 10 µm, showing a greater volume of pores of 0.1 < r < 1 µm characteristic of the matrix of lime mortars [48, 49]. Samples CA-B1-2 and CA-B2-1 are also characterized by a family of large pores of 10 < r < 100 µm. The bimodal pore size distribution with two main peaks situated at around 0.1 µm and at around 1 µm is characteristic in most of samples, except for Samples CA-M2-1 and CA-B2-3 that show a nearly unimodal pore size distribution with a main peak at around 1 µm. The Samples CA-B1-4 and CA-B2-3 not only stand out for the highest PMIP values but also for, respectively, a marked bimodal and unimodal pore size distribution (Fig. 5). The family of smaller pores is related to the aggregates porosity, although some dolostone fragments show scarce larger pores, whereas the larger pore family is related to the binder porosity (Fig. 4). Furthermore, the porosity and the pore distribution could have been modified due to deterioration, which would explain the higher porosity values and a larger pore size. The study of the hydric properties is also of great importance to evaluate the pore system and to assess the susceptibility of mortars to deterioration. Hydric tests (HT) were performed for a better study of the pore system and to evaluate the hydric behaviour of samples (Fig. 6 and Table 4). CA-M2-1 CA-M2-3 CA-AL-2 CA-AL-6 CA-R-1 CA-R-7 CA-R-8 CA-R-9 CA-B1-2 CA-B1-4 CA-B1-11 CA-B1-13 CA-B2-1 CA-B2-3 Ab 24.10 19.38 20.40 18.90 15.80 29.58 22.63 15.18 18.61 31.59 16.49 16.34 17.99 17.58 Af 25.05 20.04 20.96 19.24 16.30 31.54 25.22 16.28 19.27 33.13 19.59 17.98 22.60 17.75 Ax 3.81 3.30 2.67 1.76 3.06 6.22 10.28 6.75 3.40 4.65 15.85 9.11 20.41 1.00 S 91.95 93.40 94.46 96.92 96.37 90.25 87.76 92.16 91.84 91.16 72.91 90.65 78.78 96.00 Ca 12.05 9.69 10.20 9.45 7.90 14.79 11.32 7.59 9.31 15.79 8.24 8.17 8.99 8.79 Di 0.246 0.249 0.248 0.249 0.251 0.244 0.247 0.251 0.249 0.240 0.248 0.249 0.247 0.249 rHb 1.57 1.68 1.68 1.73 1.79 1.34 1.52 1.79 1.72 1.34 1.63 1.64 1.49 1.72 rHsk 2.59 2.54 2.59 2.59 2.53 2.31 2.47 2.52 2.58 2.40 2.39 2.33 2.26 2.48 Cc 0.040 0.024 0.022 0.030 0.010 0.023 0.021 0.014 0.028 0.028 0.022 0.020 0.017 0.029 Hc 0.81 0.65 0.65 0.65 0.58 0.65 0.97 0.65 0.78 0.97 1.16 0.97 1.03 1.18 PTH 39.3 33.8 35.1 33.3 29.2 42.2 38.4 29.1 33.2 44.3 31.9 29.6 33.8 30.5 PMIP 34.1 31.4 31.6 - 31 - 26.3 - 31 45 - 27.7 29.2 37.8 Applied Mineralogy in the Study of Historical Lime Mortars 156 The degree of pore interconnection values (Ax) was lowest in Samples CA-AL-2, CA-AL-6 and CA-B2-3 (< 3%), indicating a better pore interconnection that favours water flow though the mortar. In contrast, Samples CA-R-8, CA-B1-11, CA-B1-13 and CA-B2-1 show the highest Ax values (> 9%), which indicates greater difficulty of water to flow due to worse pore interconnection. Considering the lowest Ax values of the samples from each structure (Table 4), Sample CA-AL-6, Sample CA-M2-3 (from the south-west) and Samples CA-R-1, CA-B1-2, CA-B1-4 and CA-B2-3 (from the south-east) show the lower Ax values. Samples with better pore interconnection are those that display a higher saturation coefficient (S), since S values are related to the Ax parameter. Regarding the drying curve, at the beginning of the test the drying rate is constant. Curves closer to the vertical correspond to the samples that dry faster (Fig. 6a). Once the critical moisture content is reached the drying rate decreases and pore size and pore interconnection are the factors controlling the drying velocity [50]. Samples with highest drying index values (Di > 0.248) dry more slowly and the porous system remains full of water for longer. Samples CA-R-1 and CA-R-9 stand out for taking the longest to dry (Di = 0.251) while Sample CA-B1-4 for drying faster (Di = 0.240). Fig. 5. Pore size distribution curves of lime mortars from Amaiur Castle obtained by mercury intrusion porosimetry. (a) CA-M2-1, (b) CA-M2-3, (c) CA-AL-2, (d) CA-R-1, (e) CA-R-8, (f) CA-B1-2, (g) CA-B1-4, (h) CA-B1-13, (i) CA-B2-1, (j) CA-B2-3. Accessible pore radius (in µm) vs. incremental pore volume (in cm3/g) is represented. 8. Appendices: Published and Submitted Works 157 Fig. 6. Hydric behaviour of the lime mortars from Amaiur Castle. (a) Free water absorption, forced water absorption and drying curves. Weight variation (ΔM/M) versus time (in hours). (b) Capillarity curves. Weight variation (ΔM/S) versus time (in hours) and (c) capillarity front curves. Height (in mm) versus time (in hours). Applied Mineralogy in the Study of Historical Lime Mortars 158 Capillary uptake curves (Fig. 6b) show the typical capillary rise trend for lime mortars characterized by two different slopes [51, 52]. The first sharp slope is related to rapid water absorption at the beginning of the test. From 24 h of the test, the absorption velocity decreased and the water uptake became slow and continuous leading to a more linear slope until saturation at 250 h. Capillary front of all samples also reached the top after 24 h (Fig. 6c). The two slopes in the capillary uptake curve and the time-lag between visual and real saturation confirms the two main pore families (0.01 < r < 1 µm and 1 < r < 10 µm) detected by MIP analysis in which the family of smaller pores saturates before the family of larger pores [51]. The water amount absorbed by capillarity was higher in Samples CA-Al-6 and CA-R-7 while Samples CA-R-1 and CA-B1-2 absorbed the least amount of water. Capillarity water uptake was faster in Samples CA-M2-1, CA-B1-2, CA-B1-4, CA-B2-3 and CA-AL-6, which showed a higher capillarity coefficient (CC) (> 0.025 g/cm2 min0.5) while Samples CA-R-1 and CA-R-9 displayed the slowest values (< 0.015 g/cm2 min0.5) (Table 4). Microcracks in Samples CA-M2-1 CA-AL-6 and CA-B2-3 (Fig. 3h) could have favoured the capillarity water uptake. Open porosity values from the hydric tests (PH) were highest in Samples CA-B1-4 and CA-R-7 (44.33% and 42.17%, respectively) and lowest in south-west filling mortars (Sample CA-R-1 with 29.17% and Sample CA-R-9 with 29.11%). Considering the higher PH values of the samples from each structure (Table 4), the highest PH values were obtained for mortars from the south-east medieval wall and bastions (Samples CA-M2-1, CA-B1-2, CA-B1-4 and CA-B2-1), south-west filling mortars (Samples CA-R-7 and CA-R-8) and mortar from the lunette vault (Sample CA-AL-2). The greatest amount of water was absorbed by the samples with the highest PH values (Table 4 and Fig. 6a). Samples CA-M2-1, CA-B1-4, CA-R-7, CA-R-8 and CA-Al-2 showed the highest values (> 20%) of free water absorption (Ab) and forced water absorption (Af) and were the fastest absorbing the water (high Ca values in Table 4). Sample CA-B2-1 also absorbed a large amount of water by forced absorption. The PH values were similar to the values obtained by mercury intrusion porosimetry (PMIP). Nevertheless, the slight differences between both porosities are caused by the two different fluids used and the different exerted pressures (water at atmospheric pressure in the HT and mercury at 414 MPa in MIP analysis). Samples with the highest open porosity values show the greatest difference between skeletal and bulk densities (ρHsk and ρHb, respectively) (Table 4). 4.5. Ultrasonic Pulse Velocity Test Ultrasonic pulse velocity test is a non-destructive test that allows to evaluate features concerning the porosity and anisotropies in the mortar [53]. Table 5 summarizes values of the propagation velocity of ultrasonic primary waves (Vp) and structural anisotropy (ΔM). Table 5. Results of the ultrasonic pulse velocity test in the lime mortars from Amaiur Castle. VP1, VP2 and VP3: P-wave velocity in the three orthogonal directions (in m/s). ΔVp: Average value of the P-wave velocities. σVp: standard deviation. ΔM: structural anisotropy (%). CA-M2-1 CA-M2-3 CA-AL-2 CA-AL-6 CA-R-1 CA-R-7 CA-R-8 CA-R-9 CA-B1-2 CA-B1-4 CA-B1-11 CA-B1-13 CA-B2-1 CA-B2-3 V P1 157.61 237.70 188.17 190.22 279.28 225.16 257.58 271.60 244.27 213.06 233.90 239.13 223.77 210.42 V P2 160.40 244.09 204.82 211.18 295.77 253.73 277.31 285.09 248.06 224.49 250.03 253.77 229.39 216.81 V P3 170.27 250 193.18 193.71 290.18 230.26 272.73 277.31 264.46 215,95 235.49 239.90 244.19 219.03 ΔV p 162.76 243.93 195.39 198.37 288.41 236.38 269.21 278 252.26 217.83 239.81 244.27 232.45 215.42 σVp 6.65 6.15 8.54 11.23 8.39 15.24 10.33 6.77 10.73 5.94 8.87 8.24 10.54 4.47 ΔM 4.67 3.78 5.44 6.04 4.67 6.95 6.34 3.42 4.68 3.25 3.64 3.12 5.49 3.44 8. Appendices: Published and Submitted Works 159 P-wave velocity could vary according to the mineralogy, texture and porosity of the material [47, 54]. All studied samples show the same mineralogy with slight variations, thus the texture and porosity will be the main factors that affect the Vp values. While the variation in the velocity of the P-waves is not related to the size of aggregates, the high calcareous aggregate content favours the increase in velocity [55-57]. The higher Vp values were measured in samples with a larger amount of aggregates (Samples CA-R-1 and CA-R-9, corresponding to filling mortars from the SE area), whereas the lower values were obtained in the mortars with the lowest aggregates content (Samples CA-AL-2 and CA-AL-6 from the cistern) (Figs. 2 g-h and i, respectively). Propagation velocity of ultrasonic pulses is also affected by the porosity, with the Vp value decreasing with higher porosity [9, 57]. Accordingly, the lowest Vp values were detected in the samples with the highest porosity values as measured in MIP analysis and hydric tests (Table 4), and observed in the petrographic study (Figs. 4c and d). Besides, the small-scale anisotropies within the material such as microcracks not only affect the water circulation but also decrease the Vp values [58, 59]. Thus, the high frequency of microcracks in Sample CA-M2-1 (Fig. 4h) could explain the lowest Vp value measured in this sample (Table 5). Structural anisotropy (ΔM) confirms the heterogeneous mortar texture of all mortars. The large size of aggregates from the south-west filling mortar samples (Samples CA-R-7 and CA-R-8) explains the high ΔM values. 4.5. Colorimetry Compatibility between the repair mortar and the original mortar in terms of visual appearance is also an important requirement to consider in restoration work [4, 60]. The colour of mortars was evaluated by non-destructive colorimetric analyses using the CIELAB (CIE 1976 L*a*b*) colour space system proposed by the International Commission on Illumination (CIE). Chromatic parameters of each mortar sample are summarised in Table 6. The lightness (L*) values around 80 and the values measured for the chromatic axes (a* and b*) indicated samples with a tendency toward to the light grey field. The lower L* values were measured in Samples CA-AL-6, CA-R-8, CA-B1-4, CA-B2-1 and CA-B2-3. The a* and b* values are similar in all samples, although Samples CA-M2-1 and samples from the cistern (CA-AL-2, CA-AL-6) and from the 17th century bastion (CA-B2-1 and CA-B2-3) show higher values. The high chromatic axes values and the low L* values of samples from the 17th century bastion are explained by the presence of ceramic fragments in the mortar. Table 6. Chromatic parameters of historic lime mortar samples from Amaiur Castle. L*: Lightness, a* and b*: chromatic coordinates, C*: chroma, H: hue angle. The works and repairs carried out in the castle over time as a result of the conflicts in the region represent an additional complexity in the study of mortars. In the General Archives of Simancas, different repairs are documented, including a repair in the south-east structure of the 16th century bastion [17, 61, 62], the area where Sample CA-B1-4 was located. It could explain the clearly different hydric parameters and porosity values of this sample from the rest (Table 4). CA-M2-1 CA-M2-3 CA-AL-2 CA-AL-6 CA-R-1 CA-R-7 CA-R-8 CA-R-9 CA-B1-2 CA-B1-4 CA-B1-11 CA-B1-13 CA-B2-1 CA-B2-3 L* 80.70 83.60 82.05 77.41 80.10 85.19 77.92 80.83 81.02 84.37 83.14 79.24 79.42 73.70 a* 2.75 1.70 1.806 2.00 1.46 2.05 1.81 1.32 2.00 1.47 2.18 2.52 2.49 3.89 b* 12.06 8.76 10.76 10.94 7.87 9.02 8.37 8.76 9.99 7.76 9.77 9.56 10.44 13.99 C* 12.37 8.93 10.91 11.13 8.00 9.26 8.56 8.86 10.19 7.90 10.02 9.89 10.73 14.52 H 77.25 79.10 80.48 79.63 79.63 77.04 77.83 81.49 78.62 79.20 77.45 75.22 76.59 74.46 Applied Mineralogy in the Study of Historical Lime Mortars 160 4.6. Environmental considerations Environmental factors such as relative humidity, rainfall and temperature also affect mortar durability. Geographically, Amaiur Castle is located in the Oceanic maritime west coast climate zone (Cfb in the Köppen-Geiger climate classification) [63, 64]. Annual average relative humidity in the area of the castle is 83.4%, reaching values above 86% in some months. The average annual precipitation is around 2040 mm, with rainfall above 90 mm throughout all months of the year and reaching above 200 mm in the wettest months [65, 66]. At relative humidity values between 65% and 95%, the water vapour and water liquid coexist leading to the continuous presence of water within the pore system [45]. However, besides moistening the mortar, the meteoric water could also incorporate soluble CO2 and salts inside the pores. While dissolved CO2 favours the partial dissolution of carbonates, the volume increase due to the crystallization of secondary carbonates and/or soluble salts within the pores results in mechanical stress contributing to the mortar deterioration [67-69]. Furthermore, mortars at Amaiur Castle are exposed to continuous temperature variations since, even if the annual average temperature is 12.9 ºC, the annual absolute average minimum temperature reaches -19 ºC and the annual absolute average maximum temperature 41 ºC [65]. Continued temperature variations over time may lead to the cracking of mortar since the thermal expansion produced by the crystallisation of water into ice in colder periods also results in a mechanical stress [70]. Even if the cold and wet local environmental conditions at Amaiur Castle could have been advantageous for the hot-mixing method, since it was commonly used in cold-weather work [40], the high humidity, the continuous rainfall and the temperature variation over a broad range of the area contribute to the current weathering of Amaiur Castle lime mortars. Considering the samples from each different structure, the high porosity, high water absorption capacity and poor pore interconnection (high Ax) of Samples CA-M2-1, CA-AL-2, CA-R-7, CA-R-8 and CA-B2-1 favour mortar decay since their tortuous pore system hinders the water flow outward. Although Samples CA-B1-4 dries the fastest (low Di), its high porosity and water absorption capacity could also affect the durability. Sample CA-AL-6 is more susceptible to deterioration by capillarity since it not only absorbs a greater amount of water by capillarity but also uptakes the water faster. Furthermore, Samples CA-B1-11 and CA-B1-13 took longer to dry (high Di) and show poor pore interconnection (high Ax), which leads to water retention inside for longer, favouring mortar decay. 5. Conclusions Mineralogical, chemical and physical characterization performed in the present study has contributed to a better understanding of the historic lime mortars from Amaiur Castle and the results achieved have been able to address specific goals: Susceptibility to mortar deterioration Samples from the 14th-15th century wall show very similar mineralogical, chemical and textural characteristics, but the high presence of microcracks in the south-east sample point to its worst conservation. The poor pore interconnection of samples from the SW structure of the 16th century bastion and the SE samples of the 17th century diamond-shaped structure makes them more susceptible to decay since water is retained longer. The south-east sample from the 16th century bastion could be related to the repairs performed during the 16th century as the hydric parameters and porosity values are clearly differentiated in comparison with the rest of the samples. 8. Appendices: Published and Submitted Works 161 The water absorption capacity of samples from the lunette and barrel vault base could affect the preservation of the only cistern vault remains currently preserved. Filling mortar shows a different hydric behaviour and pore system between the south-east and south-west area. Filling mortars from the south-west area are more susceptible to deterioration not only because they show a higher porosity and water absorption capacity but also due to the poor interconnection of pores and the difficulty in drying. Environmental conditions at Amaiur Castle (high humidity, continuous rainfall and the temperature variation over a broad range) also favour the weathering of mortars. On the other hand, the high humidity conditions could have favored the hydromagnesite crystallization in the binder. Approach to technological knowledge Mineralogical and textural characterization has also allowed an exploration of the technological knowledge used in the mortar manufacturing process. Filling mortar shows larger aggregates, probably used to stabilize the mortar volume and to improve the long-term strength. Differences in aggregate size and in the physical features between the filling mortar from the south-west area and the south-east suggest at least two different filling periods. Selection of angular carbonated aggregates would have improved the mechanical strength of the mortar. Presence of hydrotalcite and hydromagnesite in the mortar binder would also have favoured the mortar strength. Identification of hydromagnesite in the present study support the use of the traditional hot-mixing method in the mortar manufacture at Amaiur Castle, a method that might have been appropriate for the damp and cold area in which the castle is located. Contribution to heritage conservation and future perspectives The present study represents a valuable reference for the suitable formulation of a compatible repair mortar that ensures the architectural heritage conservation in future restoration works at Amaiur Castle. Harsh environmental factors in the studied area make it necessary to perform future decay tests for a better assessment of historic lime mortar deterioration. The different structures from different periods at Amaiur Castle, due to changes in the defences of the building, resulted in mortars with different textural characteristics. Evolution in the Amaiur Castle defences led to the construction of different structures in different periods resulting in mortars with different textural characteristics. Future studies on the mechanical properties will be able to obtain a better understanding of changes in mortar manufacture according to the evolution of the defensive structures. Acknowledgments This study was supported by the GIC18/133 Research Group of the University of the Basque Country (UPV/EHU) and of Junta de Andalucía Research Group RNM179 and Research Project MAT2016-75889-R. G.P.-A. acknowledges the PhD research grant of the Basque Government [2015-1-02-35]. The authors also would like to thank Peter Smith for reviewing the use of English in the manuscript. Applied Mineralogy in the Study of Historical Lime Mortars 162 References [1] W. Wallace, On ancient mortars, Chemical News 11 (1865) 185-186. [2] Venice, Charter, International Charter for the Conservation and Restoration of Monuments and Sites. Available online: http://icomos.org/charters/venice_e.pdf (accessed on 27 March 2020). (1964). [3] C. Groot, G.J. Ashall, J.J. Hughes, P.J. Bartos, Characterisation of old mortars with respect to their repair: A state of the art, RILEM REPORT 28 (2007) 1. [4] L. Schueremans, Ö. Cizer, E. Janssens, G. Serré, K.V. Balen, Characterization of repair mortars for the assessment of their compatibility in restoration projects: Research and practice, Construction and Building Materials 25(12) (2011) 4338-4350. [5] ICOMOS, Declaration of Amsterdam. Available online: https://www.icomos.org/en/and/169thedeclaration-of-amsterdam (accessed on 10 January 2020). (1975). [6] N.S. Martys, C.F. Ferraris, Capillary transport in mortars and concrete Cement and Concrete Research 27(5) (1997) 747-760. [7] R.P.J. Van Hees, L. Binda, I. Papayianni, E. Toumbakari, Characterisation and damage analysis of old mortars, Materials and structures 37 (2004) 644-648. [8] C. Borges, A. Santos Silva, R. Veiga, Durability of ancient lime mortars in humid environment, Construction and Building Materials 66 (2014) 606-620. [9] A. Arizzi, G.M. Huerga, E. Sebastián, G. Cultrone, Mineralogical, textural and physicalmechanical study of hydraulic lime mortars cured under different moisture conditions, Materiales de construcción 65(318) (2015). [10] J.J. Hughes, S.J. Cuthbert, The petrography and microstructure of medieval lime mortars from the west of Scotland: Implications for the formulation of repair and replacement mortars, Materials and Structures 33(9) (2000) 594-600. [11] I. Papayianni, V. Pachta, M. Stefanidou, Analysis of ancient mortars and design of compatible repair mortars: The case study of Odeion of the archaeological site of Dion. , Construction and Building Materials 40 (2013) 84-92. [12] H. Morillas, P. Vazquez, M. Maguregui, I. Marcaida, L.F.O. Silva, Composition and porosity study of original and restoration materials included in a coastal historical construction, Construction and Building Materials 178 (2018) 384-392. [13] G. Borsoi, A.S. Silva, P. Menezes, A. Candeias, J. Mirão, Analytical characterization of ancient mortars from the archaeological roman site of Pisões (Beja, Portugal), Construction and Building Materials 204 (2019) 597-608. [14] G. Ponce-Antón, A. Arizzi, M.C. Zuluaga, G. Cultrone, L.A. Ortega, J. Agirre Mauleon, Mineralogical, Textural and Physical Characterisation to Determine Deterioration Susceptibility of Irulegi Castle Lime Mortars (Navarre, Spain), Materials 12(4) (2019) 584. [15] G. Ponce-Antón, M.C. Zuluaga, L.A. Ortega, J.A. Mauleon, Multi-analytical approach for chemical-mineralogical characterization of reaction rims in the lime mortars from Amaiur Castle (Navarre, Spain), Microchemical Journal 152 (2020) 104303. [16] I. Sagredo, Navarra. Castillos que defendieron el reino (Tomo I) de Laguardia a Foix, y del Moncayo al Goierri, Pamiela Ed., Pamplona, 2006. [17] I. Sagredo, El castillo de Amaiur a través de la historia de Navarra, Pamiela Ed., Pamplona, 2009. [18] R.L. Folk, A comparison chart for visual percentage estimation, Journal of Sedimentary Research 21(1) (1951) 32-33. [19] UNE-EN 13755 Natural stone test methods determination of water absorption at atmospheric pressure, 2008., AENOR, Madrid. [20] G. Cultrone, M.J. De La Torre, E. Sebastián, O. Cazalla, Evaluation of bricks durability using destructive and nondestructive methods (DT and NDT), Materiales de Construccion 53(269) (2003) 41-59. [21] RILEM, Recommended test to measure the deterioration of stone and to assess the differences of treatment methods., Materials and Structures 13 (1980) 175-253. [22] UNE-EN 1936, Natural stone test methods. Determination of real density and apparent density, and of total and open porosity, 2007., AENOR, Madrid. [23] NORMAL 29/88, Misura dell'indice di asciugamento (drying index), 1988., CNR-ICR, Rome. 8. Appendices: Published and Submitted Works 163 [24] UNE-EN 1925, Natural stone test methods. Determination of water absorptioncoefficient by capillarity, 2000., AENOR, Madrid. [25] ASTM D 2845-05, Standard method for laboratory determination of pulse velocities and ultrasonic elastic constants of rock, 2005., ASTM International Standards Worldwide, Pennsylvania. [26] J. Guyader, A. Denis, Wave propagation in anisotropic rocks under stress evaluation of the quality of slates, Bulletin of the International Association of Engineering Geology - Bulletin de l'Association Internationale de Géologie de l'Ingénieur 33(1) (1986) 49-55. [27] UNE-EN 15886, Conservation of cultural property. Test methods. Colour measurement of surfaces, 2011., AENOR, Madrid [28] G. Ponce-Antón, L.A. Ortega, M.C. Zuluaga, A. Alonso-Olazabal, J.L. Solaun, Hydrotalcite and Hydrocalumite in Mortar Binders from the Medieval Castle of Portilla (Álava, North Spain): Accurate Mineralogical Control to Achieve More Reliable Chronological Ages, Minerals 8(8) (2018) 326. [29] A. Arizzi, G. Cultrone, The difference in behaviour between calcitic and dolomitic lime mortars set under dry conditions: The relationship between textural and physical–mechanical properties, Cement and Concrete Research 42(6) (2012) 818-826. [30] A. Diekamp, J. Konzett, P.W. Mirwald, Magnesian lime mortars–Identification of magnesium phases in medieval mortars and plasters with imaging techniques, 12th Euroseminar on Microscopy Applied to Building Materials, Dortmund, Germany, 2009, pp. 15-19. [31] A.R. Santos, M. do Rosario Veiga, A.S. Silva, J. de Brito, J.I. Álvarez, Evolution of the microstructure of lime based mortars and influence on the mechanical behaviour: the role of the aggregates, Construction and Building Materials 187 (2018) 907-922. [32] J. Lanas, J.I. Alvarez-Galindo, Masonry repair lime-based mortars: factors affecting the mechanical behavior, Cement and Concrete Research 33(11) (2003) 1867-1876. [33] G. Cultrone, E. Sebastian, M.O. Huertas, Durability of masonry systems: A laboratory study, Construction and Building Materials 21(1) (2007) 40-51. [34] A. Arizzi, J. Martínez Martínez, G. Cultrone, D. Benavente, Mechanical evolution of lime mortars during the carbonation process, Key Engineering Materials, Trans Tech Publications2011, pp. 483-486. [35] A. Arizzi, G. Cultrone, The influence of aggregate texture, morphology and grading on the carbonation of non-hydraulic (aerial) lime-based mortars, Quarterly Journal of Engineering Geology and Hydrogeology 46(4) (2013) 507-520. [36] M. Stefanidou, I. Papayianni, The role of aggregates on the structure and properties of lime mortars, Cement and Concrete Composites 27(9-10) (2005) 914-919. [37] M. Back, M. Bauer, H. Stanjek, S. Peiffer, Sequestration of CO2 after reaction with alkaline earth metal oxides CaO and MgO, Applied Geochemistry 26(7) (2011 ) 1097-1107. [38] R.M. Dheilly, A. Bouguerra, B. Beaudoin, J. Tudo, M. Queneudec, Hydromagnesite development in magnesian lime mortars, Materials Science and Engineering A268 (1999) 127–131. [39] A. Forster, Hot-lime mortars: a current perspective, Journal of Architectural Conservation 10(3) (2004) 7-27. [40] A. Henry, J. Stewart, Practical building conservation: Mortars, renders & plasters, Practical Building Conservation. English Heritage, Surrey 2011. [41] N. Copsey, Hot mixed lime and traditional mortars : a practical guide to their use in conservation and repair, The Crowood Press, Ramsbury, Marlborough, 2019. [42] M. Zajac, S.K. Bremseth, M. Whitehead, M. Ben Haha, Effect of CaMg(CO3)2 on hydrate assemblages and mechanical properties of hydrated cement pastes at 40°C and 60°C, Cement and Concrete Research 65 (2014) 21-29. [43] A. Machner, M. Zajac, M. Ben Haha, K.O. Kjellsen, M.R. Geiker, K. De Weerdt, Limitations of the hydrotalcite formation in Portland composite cement pastes containing dolomite and metakaolin, Cement and Concrete Research 105 (2018) 1-17. [44] J. Lanas, J.I. Alvarez, Dolomitic limes: evolution of the slaking process under different conditions, Thermochimica Acta 423(1-2) (2004) 1-12. [45] M. Thomson, J.E. Lindqvist, J. Elsen, C.J.W.P. Groot, 2.5. Porosity of mortars, in: C. Groot, G. Ashall, J. Hughes (Eds.) Characterisation of Old Mortars with Respect to their Repair-State of the Art. Report of RILEM Technical Committee 167-COM, 2007, pp. 77-106. Applied Mineralogy in the Study of Historical Lime Mortars 170 Contents lists available at ScienceDirect Microchemical Journal journal homepage: www.elsevier.com/locate/microc Multi-analytical approach for chemical-mineralogical characterization of reaction rims in the lime mortars from Amaiur Castle (Navarre, Spain) Graciela Ponce-Antón a,⁎ , Maria Cruz Zuluaga a , Luis Angel Ortega a , Juantxo Agirre Mauleon b a Department of Mineralogy and Petrology, Science and Technology Faculty, University of the Basque Country (UPV/EHU), Spain b Aranzadi Society of Sciences, Spain ARTICLE INFO Keywords: Reaction rim Dedolomitization Lime mortar Hydrotalcite Hot-mixed mortars ABSTRACT This work presents a chemical-mineralogical study of archaeological lime mortars from Amaiur Castle (Navarre, Spain) dated between the 14th and 17th centuries. The study focuses on the analysis of the reaction zone observed around the dolomitic aggregates of lime mortars by means of optical microscopy, scanning electron microscopy with X-ray microanalysis, micro-Raman spectroscopy and X-ray diffraction. Multi-analytical analysis show that the reaction zone is composed of two reaction rims and a halo formed as result of the dedolomitization of dolomitic mortar aggregates in a strongly alkaline medium. The mineralogical results suggest mortars cured at around 60 °C, pointing to a traditional hot-mixing manufacture method. 1. Introduction Mortars are artificial materials composed by a mixture of inorganic binder, aggregates and some organic or inorganic additives that form a bonding material in the masonry. In basic mortar manufacture the calcium carbonate (CaCO 3 ) of the limestone used as raw material is heated in the calcination process to produce quicklime (CaO). In the slaking process water is added to calcium oxide to produce portlandite (Ca(OH) 2 ). The slaked lime and aggregates are mixed with water to make more workable putty. In the carbonation process the calcium hydroxide in the putty reacts with atmospheric carbon dioxide (CO 2 )to form calcium carbonate again. Nevertheless, during mortar manufacture other reactions could take place between the different mortar components [1,2]. Alkali-aggregate reactions (AAR) can take place during manufacture of mortar. AAR is a general term referring to all reactions occurring between binder alkalis and aggregates. AAR occurs when, in the highly alkaline medium, some aggregate mineral phases react with the alkaline hydroxides present in the hydrated lime putty. The nature, size and amount of aggregates, alkali contents, temperature and pH determine the AAR reaction speed [3]. Nevertheless, the scientific community still does not fully understand the mechanisms involved [3]. Intensive research has been carried out on AAR since it was first reported in the 1940s [4–12]. Alkali-silica reaction (ASR) and alkali-carbonate reaction (ACR) have been described within the AAR [13]. ASR involves the reaction of silica present in the siliceous limestone aggregates with the alkalis present in the binder resulting in an expansive gel. However, ACR takes place when argillaceous dolomitic limestone aggregates react with the binder alkali [3]. Several authors have described ACR in mortars and concretes since it was first recognized in the 1950s [5,14–19]. Within ACR, a dedolomitization reaction could take place. Dedolomitization involves the partial dissolution of dolomite forming a reaction zone around the edge of dolomitic aggregates [20,21]. Formation of reaction zones surrounding mortar aggregates has been described by several authors [18,22–28]. The aim of this work was to study the reaction zone in the dolomitic aggregates of Amaiur Castle (Navarre) lime mortars, and the alkali-aggregate reactions involved. A multi-analytical study was carried out for chemical, mineralogical and textural characterization by means of optical microscopy, Raman spectroscopy, X-ray diffraction and scanning electron microscopy coupled with electron-dispersive spectroscopy. In this way, the study is able to contribute knowledge of the manufacturing process of lime mortars between the14th and 17th centuries. 2. Materials and methods 2.1. Samples Archaeological lime mortar samples from Amaiur Castle (Navarre Spain) were analyzed in order to study the reaction zone in dolomitic aggregates. The mortars belong to structures built in different periods: a wall between the 14th and15th centuries, a 16th century bastion and fillings, and a second bastion dated in the 17th century (Fig. 1). https://doi.org/10.1016/j.microc.2019.104303 Received 13 May 2019; Received in revised form 3 October 2019; Accepted 3 October 2019 ⁎ Corresponding author. 0LFURFKHPLFDO-RXUQDO $YDLODEOHRQOLQH2FWREHU ;(OVHYLHU%9$OOULJKWVUHVHUYHG 7 8. Appendices: Published and Submitted Works 171 2.2. Digital and optical microscopy Macroscopic high-resolution analysis was carried out on the polished surface of bulk mortar using a Dino-Lite Premier AM7013MZT digital handheld microscope equipped with a Microtouch II sensor with adjustable polarizer with up to 200×magnification working distance. Measurement and calibration were made with DinoCapture 2.0 software. Petrographic studies were performed on polished thin-sections by polarizing microscopy using a Nikon Eclipse LV100POL microscope equipped with a DS F-11digital camera and DS L2 camera control unit. Sample microtextural characteristics were analyzed using both transmitted and reflected polarized light modes. 2.3. Raman microspectroscopy Micro-Raman analyses were performed by means of Renishaw inVia confocal microRaman spectrometer (Renishaw, Gloucestershire, UK) coupled to a DMLM Leica microscope provided with 5×,20×, 50×and 100×long working distance lenses using 785 nm (NIR) excitation laser. Laser was set at low power (not more than 1 mW at the sample) in order to avoid thermal photodecomposition. Data acquisition was carried out using Renishaw's WireTM 3.2 software package. The interpretation of Raman results was carried out by comparison of acquired Raman spectra with Raman spectra of pure standard compounds collected in the e-VISNICH dispersive Raman database. In order to obtain Raman mapping, the StreamLine technique was used. Spectra were acquired between 1000 and 1120 cm −1 with a 1 cm −1 resolution with a50×objective and a good signal-noise ratio. Internal calibrations and daily calibration with a silicon chip ensured measurement quality. 2.4. X-ray powder diffraction The X-ray diffraction (XRD) analysis was performed on a powder polycrystalline sample by means of Philips X'Pert diffractometer (Malvern PANalytical, Almelo, The Netherlands) equipped with a monochromatic Cu-ka1 X-radiation. The operating conditions were 40 kV and 20 mA. A continuous scan in the range from 5° to 70° 2θwas performed for the data collection, at an acquisition rate of 0.02° per second. Mineral phase identification was made by X'Pert HighScore Plus 3.0 software by PANalytical (Malvern PANalytical, Almelo, The Netherlands) using the experimental patterns of ICDD and ICSD diffraction databases. 2.5. Scanning electron microscopy Scanning electron microscopy and energy-dispersive X-ray spectroscopic (SEM–EDX) analyses were carried out on polished thin sections by means of a JEOL JSM-7000F Schottky-type field emission scanning electron microscope (JEOL, Tokyo, Japan) equipped with an INCA EDX X-sight Series Si (Li) Oxford pentaFET microanalysis system. The backscattered electron (BSE) resolution was 3 nm at 15 kV and 10 mm working distance. Energy dispersive X-ray spectroscopic mapping measurements were performed using an EVO 40 scanning electron microscope (Carl Zeiss STS, Germany) coupled to an X-Max energydispersive X-ray spectrometer (Oxford Instruments, Abingdon, Oxfordshire, UK). The EDX analyses were carried out using a working distance of 8–10 mm, an I Probe of 400 pA, an acceleration potential of 20 kV and 10 scans. Samples were carbon-coated to eliminate charging effects. SEM-EDS measurements were carried out to determine the elemental distribution images in the cross-section of the reaction zone. The XRD, SEM-EDX and Raman microspectroscopy analyses were performed in the Materials and Surface Unit and the Raman-LASPEA laboratory at the Advanced Research Facilities (SGIker) of the University of the Basque Country (UPV/EHU). 3. Results 3.1. Digital and optical microscopy Carbonated aggregates of mortar larger than 2 cm in size showed a pronounced reaction zone visible even at macroscopic scale. Digital microscopy observations of bulk mortar polished surfaces enabled better observation of large-size aggregate reaction zones (Fig. 2a). Observed macroscopic features were improved by the petrographic study allowing the observation of the mortar microtextural characteristics. Microscopically, mortars showed heterogeneous texture. Embedded in a micritic calcite matrix, the carbonated aggregates consisted of angular fine-grained dolostone fragments with vuggy porosity (Fig. 2b and c). Observed dolostones are secondary dolostones formed by the geological process of dolomitization in which the replacement of CaCO 3 by CaMg(CO 3 ) 2 take place [29]. Besides, the petrographic study allowed a better observation of the reaction zone of dolomitic aggregates (Fig. 2d). 3.2. Raman microspectroscopy Lime mortars were analyzed by Raman spectroscopy [30,31] and measurements were performed on a polished surface (Fig. 3a). Fig. 3b shows the recorded Raman spectra with the highest intensities of the main calcite and dolomite bands; 1087 cm −1 and 1098 cm −1 , respectively [32,33]. The main bands of calcite and dolomite overlap due to the relative shift of only 11 cm −1 , but the 1 cm −1 spectral resolution used has allowed the two intensities to be differentiated and mapped independently. Dolomite was detected in the unaltered aggregate and in some zones within the binder (Fig. 3c) whereas calcite was mainly found in the mortar binder and in the reaction zone, and scarcely within the unaltered aggregate (Fig. 3d). 3.3. X-ray diffraction XRD analyses identified different mineral phases in the mortar (Fig. 4). Aggregates are mainly composed of dolomite [CaMg(CO 3 ) 2 ] and traces of calcite [CaCO 3 ] which is in accordance with the petrographic studies (Fig. 4a). To characterize binder, a< 2 µm fraction was extracted following the procedure described by Ortega et al. [34] and Ponce Anton et al. [2]. Magnesium calcite [(Ca,Mg)CO 3 ] was identified as the principal component of mortar binder but hydrotalcite [Mg 6 Al 2 (CO 3 )(OH) 16 •4(H 2 O)] and pyroaurite [Mg 6 Fe 2 (CO 3 ) (OH) 16 •4H 2 O] phases were also present in minor amounts (Fig. 4b). Hydrotalcite and pyroaurite belong to layered double hydroxide phases (LDHs) characterized by a brucite-like structure occurring as clay-sized crystals with a general formula [M 2+ (1x) M 3+x (OH) 2 ] x+ (A n-1 ) x/n •yH 2 O where M 2+ and M 3+ are diand trivalent cations, and A n-1 is a chargebalancing anion [35–39]. The XRD pattern shows asymmetric and broad peaks at ∼11 °2θ and ∼23 °2θindicating low crystallinity and also suggesting a probable overlapping of reflection. Hydrotalcite was identified by the characteristic basal reflections d 003 = 7.61 Å at 11.63 °2θand d 006 =3.81Å at 23.33 °2θ; whereas pyroaurite was identified according to d 003 = 7.7 Å at 11.38 °2θand d 006 = 3.92 Å at 22.67 °2θ. In addition, the reflections at 23.15 °2θcorrespond to the characteristic basal plane d 012 = 3.84 Å of calcite. XRD results agree with the petrographic and Raman studies. 3.4. Scanning electron microscopy Scanning electron microscopy results on polished thin sections showed a sequence of different reaction zones (∼100 µm width) within coarse aggregate (Figs. 5,6a, 7aand8a.). Several sectors can be distinguished in the reaction zone according to textural characteristics. The reaction sectors are distributed as follows: an inner narrow reaction G. Ponce-Antón, et al. 0LFURFKHPLFDO-RXUQDO  Applied Mineralogy in the Study of Historical Lime Mortars 172 rim in contact with the unaltered dolomitic aggregate, a thicker reaction rim in the outer margin of the aggregate and a halo within the binder in contact with the outer part of the aggregate (Fig. 5). A thicker reaction rim is characterized by a pseudomorphic texture composed of dark and bright spots. Expansion cracks were not observed. EDX analyses were performed in order to characterize reaction sectors. Table 1 summarizes the major element semi-quantitative results. The reaction zone is mainly composed of MgO and CaO but MgO concentration decreases from the inner to outer zones of the aggregate while the CaO concentration increases. MgO content ranges between 33.5 to 1.2% whereas CaO varies from 65.5 to 98% showing a pronounced CaO enrichment in the reaction halo. Na 2 O, P 2 O 5 , TiO 2 and MnO appear in minor amounts (<0.2%). The SiO 2 (15.4%), Al 2 O3 (1.1%), FeO (0.8%) and K 2 O (0.3%) contents increase notably in the inner narrow rim. However, the highest FeO contents are in the thicker reaction rim (1.6%). Elemental maps were produced in order to observe element distribution in the reaction sectors. Elemental mapping shows carbon, oxygen, magnesium, calcium, aluminum and silicon spatial distribution in the aggregate, aggregate-binder interface (reaction zone) and binder (Figs. 6 and 7). In the aggregate/binder interface C and Ca concentrations increase (Figs. 6band7b, c) whereas O and Mg concentration decreases (Figs. 6c, d and 7d, e). The whitish halo clearly stands out owing to the enrichment in Ca whereas the maximum concentration of Mg is present in the aggregates (Fig. 7c and e). Although Al and Si concentrations are very low, the Si is slightly higher in the inner narrow rim (Fig. 7f and g). However, by decreasing the Si resolution on the elemental distribution map, both pixel size and intensity increase, allowing the inner narrow rim to be distinguished more clearly (Fig. 7h). Fig. 8 shows elemental mapping semi-quantitative results expressed as absolute wt%. C and Ca show the highest concentrations (83% and 71%, respectively) while O and Mg display lower concentrations (58% and 21%, respectively). The Si and Al concentration is less than 12%. When semiquantitative values are expressed as absolute wt% and are less than 25% the element distribution is not clearly observed (Fig. 8b, c, d, e). Therefore, for a better observation of the element distribution, relative wt% values were used for Mg, Al and Si elements (Fig. 8e, f, and g). Al and Mg presence in elemental mapping of binder verifies the Fig. 1. Geographic location of Amaiur Castle (Navarre, Spain). Studied samples came from the highlighted structures on the archaeological plan. In blue, 14th–15th centuries wall; in green 16th century bastion; and in reddish 17th century bastion. G. Ponce-Antón, et al. 0LFURFKHPLFDO-RXUQDO  8. Appendices: Published and Submitted Works 173 LDHs presence as identified by XRD analysis. Hexagonal crystals greater than 1 µm within the binder fraction also verify the LDHs presence (Fig. 9a and b). Mg, Al and Fe obtained by EDX (Fig. 9c) suggest the presence of hydrotalcite and pyroaurite, as was identified by XRD (Fig. 4). The silica content can be attributed to microcrystalline quartz. 4. Discussion Chemical-mineralogical results show rims and halo formation with a marked Mg loss and Ca increase pointing to chemical reactions due to dedolomitization of dolomitic aggregates (Figs. 3c, 6d, 7e, 8eand Table 1). Several authors have studied the dedolomitization reaction mechanism [20,21,40,41] and also the development of reaction zones around dolomite aggregates [18,22–28]. Two elementary reactions occur in the dedolomitization process: the first within the aggregate giving rise to a reaction rim (Eq. (1) and Eq. (2)) and the second within the binder forming a carbonate halo (Eq. (3)). Reaction rim formation takes place as follows: + +CaMg(CO ) Ca(OH) 2CaCO Mg(OH) 32 2 3 2 (1) Dolomite [CaMg(CO 3 ) 2 ] reacts with portlandite [Ca(OH) 2 ] to generate calcite [CaCO 3 ] and brucite [Mg(OH) 2 ]. Once calcite and brucite precipitate, a reaction rim on the edge of the dolomite aggregate is formed (Fig. 5). Dissolution of dolomite is influenced by temperature and alkaline medium [20,21]. Unlike limestone, dolostones are unstable in alkaline environments [13]. Thus, in alkaline environments, dolomite reacts with hydroxyl ions [OH − ] to form calcite, brucite and carbonate ions [CO 32− ] as follows: +++CaMg CO OH CaCO Mg OH CO()2 () 32 323 2 (2) Carbonate halos are formed within the binder in contact with the outer part of the dolomitic aggregate by the carbonation of lime putty. A halo is not formed by the putty carbonation bias to the reaction with atmospheric carbon dioxide but due to the reaction between dolomitic aggregate and alkalis leading to in situ calcite precipitation [11]. For the halo formation, the CO 32− liberated by dedolomitization reaction Fig. 2. Archaeological mortar samples showing reaction zones at the edge of the dolomitic aggregate: (a) stereomicroscopic image of the reaction zone; (b) mortar photomicrograph; (c) mortar photomicrograph showing vuggy porosity; (d) detail of the aggregate reaction zone. A = aggregate, B = binder, R = rim, VP = vuggy porosity. Fig. 3. Optical and chemical results of aggregate edge Raman analysis: (a) optical microscopy image; (b) Raman spectra of the mapped areas with the highest intensities of the 1098 cm -1 dolomite band and the 1087 cm -1 calcite band; (c) Raman microscopy map showing dolomite distribution; (d) Raman microscopy map showing calcite distribution. G. Ponce-Antón, et al. 0LFURFKHPLFDO-RXUQDO  Applied Mineralogy in the Study of Historical Lime Mortars 174 migrates into the lime putty and reacts with portlandite to produce calcite and OH − [42] as follows: + +CO Ca OH OH CaCO() 2 3 22 3 (3) Reaction rims and carbonate halo formation do not produce expansion but favor the high alkaline environment [18,19]. Besides, water dissociates in a reversible reaction in which both hydrogen ions (H + )andOH − are generated. With a higher pH, faster dedolomitization reactions take place [26,42]. Although calcite and brucite are formed as dedolomitization products (Eq. (1) and Eq. (2)), brucite could not be identified by XRD since the small size of the reaction rim did not allow the extraction of a representative powder sample without aggregate and matrix contamination. However, dark and bright spots observed in BSE at the thicker reaction rim (Fig. 5) could be identified as brucite and calcite, respectively, forming a pseudomorphic texture [18]. Moreover, the elemental mapping of Ca and Mg concentrations also suggests the presence of brucite since Ca concentration decreases in dark spots while Mg concentration increases (Figs. 7cand8c, f). EDX analysis shows Ca enrichment in the halo in accordance with Eq. (3) (Table 1 and Fig. 7c). The siliceous narrow rim can be explained as result of an alkalisilicate reaction (ASSR) (Figs. 5 and 7g, h). The ASSR is a specific type of alkali-silica reaction (ASR) that occurs more slowly [3]. In an ASR, silica in siliceous aggregates reacts with alkali solution forming an unstable silica gel (ASR-gel) which absorbs water and expands causing the formation of cracks [6,19]. However, when the phyllosilicates within aggregates react with the alkaline solution, ASSR occurs resulting in small amount of silicate gel (ASSR-gel) [3,18,43]. Phyllosilicates appear scattered in dolostones as impurities and in contact with an alkaline medium react and break down [13]. Unlike ASR-gel composed of alkalis, calcium, silica and water, the ASSR-gel is composed of alkalis (potassium), silica, aluminum and iron [44]. To form the siliceous narrow rim, the ASSR-gel reacts with brucite to form non-expansive Mg-silicate-gel that in turn reacts with brucite to form “chlorite-like” phases [19,23,25]. Neither phyllosilicates from the dolomitic aggregate nor reaction products in the siliceous narrow rim could be identified by XRD due to the scarce amount of impurities in aggregates and the small size of the rim, respectively. However, the Si, Al, Fe and K contents of the siliceous narrow rim (Table 1) suggest the presence of “chlorite-like” phases in the rim as well as phyllosilicates in the dolomitic aggregate. According to chemical results, chlorite [(Mg,Fe) 5 Al(Si 3 Al)O 10 (OH) 8 ] and illite [K(Al,Mg,Fe) 2 (Si,Al) 4 O 10 (OH) 2 ] are the expected phyllosilicates in dolostone aggregates. Higher Si concentration in the narrow rim can be related to the presence of magnesium silicate hydrate (M–S–H) phases as reaction products. M–S–H phases (short for (MgO) x –(SiO 2 ) y –(H 2 O) z ) show a layered structure similar to phyllosilicates [45–48]. The crystalline structure of M-S-H synthetic phases has been related to the poorlycrystalline trioctahedral (2:1 or 1:1) phyllosilicates crystalline structures [49] and have also been associated with sepiolite [Mg 4 Si 6 O 15 (OH) 2 •6H 2 O] [45]. Like phyllosilicates, M–S–H phases are stable in an alkaline environment at pH up to 10 [46,49–51]. Fig. 4. X-ray diffraction patterns of mortar components: (a) mortar dolomitic aggregate spectrum; (b) mortar binder fraction less than 2 µm spectrum. Dol = dolomite, Cal = calcite, Qtz = quartz, HT = hydrotalcite, Prt = pyroaurite. Fig. 5. SEM-BSE image of lime mortar polished thin-section. Different reaction zones are observed. A = aggregate, B = binder, NRR = narrow reaction rim, TRR = thick reaction rim, H = halo. . Fig. 6. SEM-BSE image and elemental mapping of reaction zone of dolomitic aggregate: (a) BSE image; (b) SEM-EDS distribution image for calcium; (c) SEMEDS distribution image for oxygen; (d) SEM-EDS distribution image for magnesium. G. Ponce-Antón, et al. 0LFURFKHPLFDO-RXUQDO  8. Appendices: Published and Submitted Works 175 Amorphous M-S-H formation have been also identified during the hydration of binder materials with a high content in MgO [45]. However, it was not possible to confirm the presence of M-S-H phases in the studied mortars. Hydrotalcite rims have also been described surrounding dolomitic aggregates [19,52,53]. In view of the results of the elemental mapping, the absence of aluminum in the reaction zone does not indicate the presence of hydrotalcite. However, elemental mapping shows Al and Mg concentrations in the binder suggesting a presence of hydrotalcite in the binder (Fig. 8f, g). In fact, hydrotalcite and pyroaurite were also identified in the binder by XRD (Fig. 4). Hexagonal plate-like crystals characteristic of hydrotalcite and pyroaurite LDH phases were observed by SEM, confirming the elemental mapping and XRD results (Fig. 9a and b). Additionally, the silica in the binder (Fig. 7g, h and 9c) can proceed from phyllosilicate breakdown [26] leading to microcrystalline quartz, which was the only silicate phase identified by XRD (Fig. 4b). Hydrotalcite could be formed in the mortar manufacture during the slaking process [2]. The Mg(OH) 2 and CO 32− released from dedolomitization reactions (Eqs. (1) and (2)) and the aluminate ions [Al (OH) 4− ] released from phyllosilicate breakdown can migrate into the lime putty and react forming hydrotalcite [26,52,54]. Besides, the lime could also contain MgO and Al 2 O 3 when impure limestone and/or partially dolomitized limestones have been used in lime production, and when they rehydrate and react they form hydrotalcite [2,55–57]. Furthermore, the LDHs are characterized by a high capacity to capture CO 32− anions due to their ion-exchange properties [35]. Besides, the high CO 32− affinity of LDHs makes it possible to incorporate the dead carbon from the CO 32− of aggregates [35,58]. Therefore, the hydrotalcite LDH phase constitutes a potentially contaminating mineral phase in radiocarbon dating of the mortar binder [2]. Hydrated calcium aluminate phases (AFm) with general formula [Ca 2 (Al,Fe)(OH) 6 ]•X•xH2O where X is a monovalent or half of a divalent anion [52,59] were not identified in studied mortars since the hydrotalcite mineral phase is thermodynamically more stable [60]. The formation of hydrotalcite has been described in dolomitic mortars cured at 60 °C [52,53]. The presence of hydrotalcite in the studied mortars Fig. 7. Detailed SEM-BSE image and elemental mapping of reaction zone: (a) BSE image; (b) SEM-EDS distribution image for carbon; (c) SEM-EDS distribution image for calcium; (d) SEM-EDS distribution image for oxygen; (e) SEM-EDS distribution image for magnesium; (f) SEM-EDS distribution image for aluminium; (g) SEM-EDS distribution image for silicon; (h) SEM-EDS higher magnification image for silicon distribution. Fig. 8. Detailed SEM-BSE image and semiquantitative elemental mapping of reaction zone with percentages indicated on a colour scale: (a) SEM-BSE image; (b)–(e) absolute wt% for carbon, calcium, oxygen and magnesium, respectively; (f)-(h) relative wt% of magnesium, aluminium and silicon, respectively. G. Ponce-Antón, et al. 0LFURFKHPLFDO-RXUQDO  Applied Mineralogy in the Study of Historical Lime Mortars 176 points to mortars cured at around 60 °C, suggesting the traditional hotmixing method in mortar manufacture. In the hot-mixing method, quicklime (CaO) is mixed with the aggregates and slaked to use it later when it is still hot [61,62]. Quicklime is highly reactive in contact with water resulting in a strong exothermic reaction [63] leading to temperatures that may reach 200 °C when it is slaked with a little water and drop below 100 °C as more water is added until slaking finishes at around 58 °C [62]. Therefore, the hot-mixing method leads to both portlandite and hydroxyl ion formation during the slaking (Eq. (4) and Eq. (5), respectively) favoring the dedolomitization reactions according to Eq. (1) and Eq. (2), respectively. +CaO H OàCa(OH) 2 2 (4) ++ + CaO H OàCa 2OH 2 2 (5) Hot-mixed mortar production was relatively cheap and quick to manufacture since quicklime could be used shortly after it was produced, thus also reducing storage problems [63,64]. Hot-mixed mortars had excellent workability and were commonly used for foundation works and core filling principally in cold-weather or winter work [61,63]. These characteristics would be advantageous in the typically cold and wet climate conditions in the region where Amaiur Castle is located [65]. Besides, the cheap and quick hot-mixed mortar manufacture would be appropriate in the construction and modification of Amaiur Castle structures in conflictive periods. 5. Conclusions A combination of optical microscopy, micro-Raman spectroscopy, X-ray diffraction and scanning electron microscopy with X-ray microanalysis was able to characterize the reaction zone of dolomitic aggregates in Amaiur Castle historic mortars. Chemical, mineralogical and textural variations in the dolomitic aggregate reaction zone show the presence of two reaction rims within the aggregate and a halo within the binder. Rims and halo were formed due to an alkali-aggregate reaction (AAR) leading to dedolomitization of dolomitic mortar aggregates in a strongly alkaline medium, although an alkali silicate reaction (ASSR) was also involved. Neither AFm nor M-S-H phases were detected in the studied mortar lime binder but hydrotalcite and pyroaurite were identified. The presence of hydrotalcite and pyroaurite advises against the use of lime binders from Amaiur Castle for radiocarbon dating. Mortar chemical and mineralogical characteristics point to the use of the traditional hot-mixing method in the mortar manufacture at Amaiur Castle. Declaration of Competing Interest Authors declare that they have no conflict of interest. Acknowledgments The authors would like to thank the anonymous referee for their comments and suggestions on the manuscript. The study was supported by the IT1193-19 Research Group of the Basque Country Government. G.P.-A. also acknowledges a PhD research grant from the Basque Country Government [PRE-2015-1-0235]. The authors would like to thank Peter Smith for reviewing the use of English in the manuscript. References [1] D.T. Beruto, R. Vecchiattini, M. Giordani, Solid products and rate-limiting step in the thermal half decomposition of natural dolomite in a CO2 (g) atmosphere, Thermochim. Acta 405 (2003) 183–194. [2] G. Ponce-Antón, L.A. Ortega, M.C. Zuluaga, A.Alonso Olazabal, J.L. Solaun, Hydrotalcite and hydrocalumite in Mortar Binders from the Medieval Castle of Portilla (Álava, North Spain): accurate mineralogical control to achieve more reliable chronological ages, Minerals 8 (2018) 326. [3] J.M.M.da Fonseca, V.K.B. de Souza, D.G.C.da Silva, D.L.da Silva, E.C.B. Monteiro, Alkali-aggregate reaction: definition, influence and control, Eng. Appl. Sci. 3 (2018) 12. [4] T.E. Staton, Expansion of concrete through reaction between cement and aggregate, Proc. Am. Soc. Civil Eng. 66 (1940) 1781–1811. [5] J.E. Gillott, Alkali-aggregate reactions in concrete, Eng. Geol. 9 (1975) 303–326. [6] L.D. Glasser, N. Kataoka, The chemistry of ‘alkali-aggregate'reaction, Cem. Concr. Res. 11 (1981) 1–9. [7] S. Diamond, Alkali aggregate reactions in concrete: an annotated bibliography 1939–1991, Document SHRP-C/UPW-92-601, Strategic Highway Research Program, National Research Council, Washington, DC, 1992. [8] E.J. Lee, H.M. Clowes, Alkali-Aggregate Reaction 1977-1992, A Definitive Bibliography, BCA Ref: CIS/B8, British Cement Association, Slough (later Crowthorne), U.K, 1992. [9] A.B. Poole, The alkali–silica reactions in concrete, in: S. NR (Ed.), Introduction to Alkali Aggregate Reaction in Concrete, Blackie & London, UK, 1992, pp. 1–28. [10] B. Fournier, M.-A. Bérubé, Alkali-aggregate reaction in concrete: a review of basic concepts and engineering implications, Can. J. Civ. Eng. 27 (2000) 167–191. [11] l. Sims, A. Poole, Alkali–aggregate reactivity, in: J. Newman, C. Ban Seng (Eds.), Table 1 Chemical analysis results obtained by EDX of major elements expressed as oxides in wt%. Analysis Zone Na 2 OMgO CaO Al 2 O 3 SiO 2 FeO K 2 OP 2 O 5 TiO 2 MnO Point 1 - Aggregate 0.10 33.51 65.45 0.20 0.38 0.02 0.06 0.09 0.19 Point 2 - Narrow rim 18.58 63.55 1.11 15.40 0.83 0.29 0.04 0.04 0.17 Point 3 - Thicker rim 4.14 91.44 0.26 2.08 1.57 0.09 0.17 0.17 0.09 Point 4 - Halo 0.12 1.19 98.03 0.03 0.42 0.06 0.01 0.14 Fig. 9. Mortar binder SEM-EDX results: (a) and (b) Secondary electron SEM images showing LDHs hexagonal crystals; (c) EDX spectrum of the marked area. G. Ponce-Antón, et al. 0LFURFKHPLFDO-RXUQDO  8. Appendices: Published and Submitted Works 177 Advanced Concrete Technology – Concrete Properties, Elsevier, Oxford, U.K, 2003, pp. 1–37. [12] G.E. Blight, M.G Alexander, Alkali-Aggregate Reaction and Structural Damage to Concrete: Engineering Assessment, Repair and Management, CRC Press, 2011. [13] F.H. Shrimer, Progress in the Evaluation of Alkali-Aggregate Reaction in Concrete Construction in the Pacific Northwest 2209-K Geological Survey Bulletin, United States and Canada. U. S, 2005, p. 11. [14] E.G. Swenson, A reactive aggregate undetected by ASTM tests, ASTM Bull. 226 (1957) 48–51. [15] E.G. Swenson, J.E. Gillott, Characteristics of Kingston carbonate rock reaction, Highway Res. Board Bull. 275 (1960). [16] D.W. Hadley, Alkali reactivity of carbonate rocks-expansion and dedolomitization, Highway Research Board Proceedings, 40 1961. [17] M.-S. Tang, Z. Liu, Y.-N. Lu, S.-F. Han, Alkali-carbonate reaction and pH value, Il Cemento 88 (1991) 141–150. [18] T. Katayama, How to identify carbonate rock reactions in concrete, Mater. Charact. 53 (2004) 85–104. [19] T. Katayama, The so-called alkali-carbonate reaction (ACR) — its mineralogical and geochemical details, with special reference to ASR, Cem. Concr. Res. 40 (2010) 643–675. [20] S. Galı , C. Ayora, P. Alfonso, E. Tauler, M. Labrador, Kinetics of dolomite–- portlandite reaction: application to portland cement concrete, Cem. Concr. Res. 31 (2001) 933–939. [21] E. Garcı a, P. Alfonso, E. Tauler, S. Galı , Surface alteration of dolomite in dedolomitization reaction in alkaline media, Cem. Concr. Res. 33 (2003) 1449–1456. [22] R.E. Bisque, J. Lemish, Chemical characteristics of some carbonate aggregate as related to durability of concrete, Highway Research Board Bulletin (1958). [23] D.W. Hadley, Alkali reactivity of dolomitic carbonate rocks, Highway Research Record 45 (1964). [24] H.N. Walker, Reaction products in expansion test specimens of carbonate aggregate, Transp. Res. Rec. 525 (1974) 28–37. [25] A.B. Poole, P. Sotiropoulos, Reactions between dolomitic aggregate and alkali pore fluids in concrete, Q. J. Eng. Geol. Hydrogeol. 13 (1980) 281–287. [26] G.-L. Gan, P.G. Spry, A.M. Cody, Rim formation on iowa highway concrete dolomite aggregate: the effects of dedolomitization reactions, Environ. Eng. Geosci. (1996) 59–72 II. [27] T. Katayama, T. Drimalas, J.H. Ideker, B. Fournier, Rim-forming dolomitic aggregate in concrete structures in Saudi Arabia - is dedolomitization equal to the socalled alkali-carbonate reaction? 14th International Conference on Alkali Aggregate Reactions (ICAAR), Austin, Texas, 2012. [28] S. Kramar, V. Zalar, M. Urosevic, W. Körner, A. Mauko, B. Mirtič, J. Lux, A. Mladenović, Mineralogical and microstructural studies of mortars from the bath complex of the Roman villa rustica near Mošnje (Slovenia), Mater. Charact. 62 (2011) 1042–1057. [29] J.S. Boggs, Petrology of Sedimentary Rocks, second ed., Cambridge University Press, Cambridge, 2009. [30] S. Martinez-Ramirez, S. Sanchez-Cortes, J.V. Garcia-Ramos, C. Domingo, C. Fortes, M.T. Blanco-Varela, Micro-Raman spectroscopy applied to depth profiles of carbonates formed in lime mortar, Cem. Concr. Res. 33 (2003) 2063–2068. [31] T. Schmid, P. Dariz, Chemical imaging of historical mortars by Raman microscopy, Constr. Build. Mater. 114 (2016) 506–516. [32] J. Sun, Z. Wu, H. Cheng, Z. Zhang, R.L. Frost, A Raman spectroscopic comparison of calcite and dolomite, Spectrochim. Acta Part A 117 (2014) 158–162. [33] S. Gunasekaran, G. Anbalagan, S. Pandi, Raman and infrared spectra of carbonates of calcite structure, J. Raman Spectrosc. 37 (2006) 892–899. [34] L.A. Ortega, M.C. Zuluaga, A. Alonso-Olazabal, X. Murelaga, M. Insausti, A. IbañezEtxeberria, Historic lime-mortar 14C dating of Santa María la Real (Zarautz, northern Spain): extraction of suitable grain size for reliable 14C dating, Radiocarbon 54 (2012) 23–36. [35] S. Miyata, Anion-exchange properties of hydrotalcite-like compounds, Clays Clay Miner. 31 (1983) 305–311. [36] M. Meyn, K. Beneke, G. Lagaly, Anion-exchange reactions of layered double hydroxides, Inorg. Chem. 29 (1990) 5201–5207. [37] K. Rozov, U. Berner, C. Taviot-Gueho, F. Leroux, G. Renaudin, D. Kulik, L.W. Diamond, Synthesis and characterization of the LDH hydrotalcite–pyroaurite solid-solution series, Cem. Concr. Res. 40 (2010) 1248–1254. [38] S.J. Mills, A.G. Christy, J.-M.R. Génin, T. Kameda, F. Colombo, Nomenclature of the hydrotalcite supergroup: natural layered double hydroxides, Mineral. Mag. 76 (2012) 1289–1336. [39] D.G. Evans, R.C.T. Slade, Structural aspects of layered double hydroxides, in: X. Duan, D.G. Evans (Eds.), Layered Double Hydroxides, Springer Berlin Heidelberg, Berlin, Heidelberg, 2006, pp. 1–87. [40] E. Busenberg, L.N. Plummer, The kinetics of dissolution of dolomite in CO2-H2O systems at 1.5 to 60°C C and 0 to 1atm PCO2, Geochim, Cosmochim. Acta 282 (1982) 45–78. [41] X. Zhang, F.P. Glasser, K.L. Scrivener, Reaction kinetics of dolomite and portlandite, Cem. Concr. Res. 66 (2014) 11–18. [42] T. Prinčič, P. Štukovnik, S. Pejovnik, G. De Schutter, V. Bokan Bosiljkov, Observations on dedolomitization of carbonate concrete aggregates, implications for ACR and expansion, Cem. Concr. Res. 54 (2013) 151–160. [43] D.W. Hobbs, Alkali-Silica Reaction in Concrete, Thomas Telford, London, 1988. [44] J. Smeltz, J. Farver, Dedolomitization and Alkali Reactions in Ohio-sourced Dolstone Aggregates (No. FHWA/OH-2017-9), Deptartment of Transportation, Ohio, 2017. [45] D.R.M. Brew, F.P. Glasser, Synthesis and characterisation of magnesium silicate hydrate gels, Cem. Concr. Res. 35 (2005) 85–98. [46] D. Nied, K. Enemark-Rasmussen, E. L'Hopital, J. Skibsted, B. Lothenbach, Properties of magnesium silicate hydrates (M-S-H), Cem. Concr. Res. 79 (2016) 323–332. [47] C. Roosz, S. Grangeon, P. Blanc, V. Montouillout, B. Lothenbach, P. Henocq, E. Giffaut, P. Vieillard, S. Gaboreau, Crystal structure of magnesium silicate hydrates (M–S–H): the relation with 2:1 Mg–Si phyllosilicates, Cem. Concr. Res. 73 (2015) 228–237. [48] S.A. Walling, H. Kinoshita, S.A. Bernal, N.C. Collier, J.L. Provis, Structure and properties of binder gels formed in the system Mg(OH)2–SiO2–H2O for immobilisation of Magnox sludge, Dalton Trans. 44 (2015) 8126–8137. [49] E. Bernard, B. Lothenbach, C. Cau-Dit-Coumes, C. Chlique, A. Dauzères, I. Pochard, Magnesium and calcium silicate hydrates, part I: investigation of the possible magnesium incorporation in calcium silicate hydrate (C-S-H) and of the calcium in magnesium silicate hydrate (M-S-H), Appl. Geochem. 89 (2018) 229–242. [50] E. Bernard, B. Lothenbach, F. Le Goff, I. Pochard, A. Dauzères, Effect of magnesium on calcium silicate hydrate (C-S-H), Cem. Concr. Res. 97 (2017) 61–72. [51] E. Bernard, B. Lothenbach, D. Rentsch, I. Pochard, A. Dauzères, Formation of magnesium silicate hydrates (M-S-H), Phys. Chem. Earth, Parts A/B/C 99 (2017) 142–157. [52] M. Zajac, S.K. Bremseth, M. Whitehead, M. Ben Haha, Effect of CaMg(CO3)2 on hydrate assemblages and mechanical properties of hydrated cement pastes at 40°C and 60°C, Cem. Concr. Res. 65 (2014) 21–29. [53] A. Machner, M. Zajac, M. Ben Haha, K.O. Kjellsen, M.R. Geiker, K. De Weerdt, Limitations of the hydrotalcite formation in Portland composite cement pastes containing dolomite and metakaolin, Cem. Concr. Res. 105 (2018) 1–17. [54] P. Sipos, The structure of Al(III) in strongly alkaline aluminate solutions — a review, J. Mol. Liq. 146 (2009) 1–14. [55] S. Miyata, A. Okada, Synthesis of hydrotalcite-like compounds and their physicochemical properties-the systems Mg2+-Al3+-SO4 2and Mg2+-Al3+-CrO4 2, Clays Clay Miner. 25 (1977) 14–18. [56] S. Miyata, Physico-chemical properties of synthetic hydrotalcites in relation to composition, Clays Clay Miner. 28 (1980) 50–56. [57] J. Schork, Dolomitic lime in the US, J. Arch. Conserva. 18 (2012) 7–25. [58] K. Grover, S. Komarneni, H. Katsuki, Synthetic hydrotalcite-type and hydrocalumite-type layered double hydroxides for arsenate uptake, Appl. Clay Sci. 48 (2010) 631–637. [59] H.F.W. Taylor, Cement Chemestry, Thomas Telford, London, 1997. [60] Z. Maciej, M. Ben Haha, Hydration of limestone and dolomite cement, 14th International Congress on the Chemistry of Cement, Beijing, China, 2015. [61] E. Heritage, Practical Building Conservation: Mortars, Renders & Plasters, Ashgate, Surrey, 2011. [62] N. Copsey, Hot Mixed Lime and Traditional Mortars: A Practical Guide to Their Use in Conservation and Repair, The Crowood Press, Ramsbury, Marlborough, 2019. [63] A. Forster, Hot-lime mortars: a current perspective, J. Arch. Conserv. 10 (2004) 7–27. [64] J. Válek, T. Matas, Experimental study of hot mixed mortars in comparison with lime putty and hydrate mortars, Historic Mortars, Springer Netherlands, Dordrecht, 2012, pp. 269–281. [65] Arizkun. Available online:http://meteo.navarra.es/climatologia/selfichaclima.cfm? IDEstacion=66&tipo=MAN(accessed on 3 May 2019). G. Ponce-Antón, et al. 0LFURFKHPLFDO-RXUQDO  Applied Mineralogy in the Study of Historical Lime Mortars 178 8. Appendices: Published and Submitted Works 179 APPENDIX III.2 Petrographic and chemical-mineralogical characterization of mortars from the cistern at Amaiur Castle (Navarre, Spain) Graciela Ponce-Antón, Maria Cruz Zuluaga, Luis Angel Ortega, Juantxo Agirre Mauleon Minerals 2020; 10(4):311 Minerals 2020,10, 311 5 of 16 Micro-RamananalyseswereperformedusingaRenishawinViaconfocalmicroRamanspectrometer (Renishaw inVia, Gloucestershire, UK). Spectra were acquired between 1000 and 1120 cm 1 with a 1 cm resolution and the data acquisition was carried out using Renishaw’s WireTM 3.2 software package (Renishaw, Gloucestershire, UK). Raman spectra of pure standard compounds collected in the e-VISNICH dispersive Raman database were used to interpret the results. Fourier transform infrared spectroscopy (FTIR) by the potassium bromide pellet technique was carried out to determine the nature of the organic compounds using a JASCO 4200 FTIR spectrometer (JASCO INTERNATIONAL CO., Hachioji, Tokyo, Japan) and acquiring spectra between 400 and 4000 cm1. To improve the FTIR signal of the organic components, an extraction was conducted using 200 µ L of dichloromethane organic solvent. Hydraulicity Index (HI) (Equation (1)) and Cementation Index (CI) (Equation (2)) values were calculated to assess the hydraulicity of the binder according to Boynton formula [ 24 , 25 ]. Indices were calculated as below: HI =SiO2+Al2O3 CaO +MgO , (1) CI =2.8SiO2+1.1Al2O3+0.7Fe2O3 CaO +1.4MgO . (2) 4. Results 4.1. Petrographic and Chemical–Mineralogical Characterization Macroscopically, a di↵erence in the nature of aggregates was observed between the plaster (Figure 3a), mortars from the tank (Figure 3b–d), and the mortars from the vault (Figure 3e,f). Sample CA-AL-2 from the lunette of the vault and Samples CA-AL-5 and CA-AL-6 from the base of the barrel vault (structural mortars) show carbonated aggregates, whereas Samples CA-AL-7, CA-AL-8 and CA-AL-9 (structural mortars), and Sample CA-AL-1 (plaster) show siliceous aggregates. Mortars from the tank also show increasing aggregate grading, from structural mortars (inner part; Samples CA-AL-7, CA-AL-8, and CA-AL-9) to the plaster (outer part; Sample CA-AL-1) (Figure 3). ! Figure 3. Macroscopic texture of the lime mortars from the Amaiur Castle cistern. ( a ) CA-AL-2, plaster sample. ( b ) CA-AL-8a, ( c ) CA-AL-8b, and ( d ) CA-AL-7, samples from the tank mortars. ( e ) CA-AL-2 and ( f ) CA-AL-5, mortars from the vault. Mortars from the tank show an increase in aggregate grading from the inner part (d) to the outer part (a). Microscopically, all samples show a heterogeneous binder matrix-supported texture with aggregates embedded in a micritic calcite matrix. Petrographic observations of mortar identified the carbonated aggregates of samples from the vault as poorly sorted fine-grained dolostone fragments with angular to subangular shape (Figure 4a). The grain sizes of aggregates from the vault base (Samples CA-AL-5 and CA-AL-6) range from 0.2 mm up to 3 mm, whereas aggregates from the lunette 8. Appendices: Published and Submitted Works 187 Minerals 2020,10, 311 6 of 16 (CA-AL-2) reach 8 mm in size. Dolostone aggregates show a pronounced reaction zone (Figure 4a). Scarce ceramic fragments can also be observed dispersed in the binder matrix. Figure 4. Photomicrographs showing the most representative microtextures of the lime mortars from Amaiur Castle cistern. ( a ), ( b )-left, ( c ) and ( d )-left: plane polarized light mode (PPL). ( b )-right, ( d )-right, ( e , f ): crossed-polarized light mode (XPL). C: ceramic; DRx: dolostone; L: lime lump; PhRx: phyllite; PL: pigmented layer; QRx: quartzite; Qz: quartz; R: reaction zone; ScRx: Schist; SvRx: subvolcanic rock. The nature of the aggregates from the cistern tank mortars is the same in both structural mortars (Samples CA-AL-7, CA-AL-8, and CA-AL-9) and plaster (Samples CA-AL-1). Mortars are mainly composed of subangular to rounded ceramic fragments (s.l.), and the siliceous aggregates observed macroscopically have been identified as well-rounded quartz grains and phyllite, schist, quartzite, sandstone, and subvolcanic rocks (Figure 4b–e). Dolostone fragments were also observed in minor amounts, and also some charcoal fragments were dispersed in the binder matrix. Heterometric lime lumps up to 4 mm were also observed (Figure 4e). The grain size of aggregates decreases and aggregate sorting increases from the inner layer of the structural mortar (Sample CA-AL-7) to the outer part (CA-AL-8 and CA-AL-9). Sample CA-AL-7 shows very poorly sorted aggregates from 0.7 mm to 2 cm in size. The outer part of Sample CA-AL-8 (CA-AL-8a) is very similar to Sample CA-AL-9, with smaller and more sorted aggregates than the Applied Mineralogy in the Study of Historical Lime Mortars 188 Minerals 2020,10, 311 7 of 16 inner part of Sample CA-AL-8 (CA-AL-8b). Both Subsample CA-AL-8b and Sample CA-AL-9 show moderately sorted aggregates ranging from 0.2 mm up to 3 mm in grain size, whereas Subsample CA-AL-8a shows better sorted aggregates from 0.1 to 1.3 mm in size. Sample CA-AL-1 corresponding to the plaster mortar consists of two di↵erent layers (Figure 4f). The inner layer of the plaster is also composed by the well-rounded and sorted ceramic and polygenic rock aggregates, as observed in the structural mortars of the cistern, which are up to 0.3 mm in size. The outer layer of the plaster is a reddish pigmented layer around 0.15 mm thick showing a scarce amount of mica-like phyllosilicates and quartz grains. Binder/aggregate ratios were defined by the comparison of the chart for volume percentage estimation [ 26 ]. Samples show a binder/aggregate ratio between 1:2 and 1:1, except for Sample CA-AL-7, which shows a binder/aggregate ratio of 1:1 and the inner layer of plaster, which shows a binder/aggregates ratio of 2:1. To determine the composition of the mortar binders, Sample CA-AL-2 from the vault lunette, Sample CA-AL-9 from the structural mortars of the tank, and both inner and pigmented layers of plaster (Sample CA-AL-1) were selected for X-ray di↵raction (XRD) analysis. A binder fraction <2 µ m of Samples CA-AL-2 and CA-AL-9 was extracted in order to avoid the interference of the aggregate composition following the procedures described by Ortega et al. [ 27 ]and Ponce-Anton et al. [ 28 ]. The small amount of Sample CA-AL-1 from the plaster made it impossible to extract the binder fraction <2 µ m, and thus the bulk fraction of both inner and pigmented layers was analysed. For the analysis of the inner layer, the aggregates observable with the naked eye were removed. The XRD results are shown in Figure 5. All samples are mainly composed of magnesium calcite [(Ca, Mg)CO 3 ], and in minor amounts, hydrotalcite [Mg 6 Al 2 (CO 3 )(OH) 16· 4(H 2 O)] was also detected in all samples, except in the pigmented layer where only traces were detected. Quartz [SiO 2 ] and illite-like phyllosilicates were detected in samples from the cistern tank in both structural and plaster mortars. Reflection peaks at 7.03 Å and 3.51 Å allowed to detect small amounts of the amesite mineral phase [Mg 2 Al 2 SiO 5 (OH) 4 ] in Sample CA-AL-9 and in the inner layer of the plaster. Hematite [Fe 2 O 3 ] was also identified in the pigmented outermost layer of the plaster. Figure 5. X-ray di↵raction patterns of the lime mortars from Amaiur Castle cistern. ( a ) Binder fraction <2 µ m from the lunette. ( b ) Binder fraction <2 µ m from the structural mortar of the tank. ( c ) Bulk fraction from the inner layer of the plaster mortar. ( d ) Bulk fraction from the pigmented layer of the plaster mortar. Ame: amesite, Hem: hematite, HT: hydrotalcite; Mg-cal: magnesium calcite, Phy: phyllosilicates s.l., Qz: quartz. 8. Appendices: Published and Submitted Works 189 Minerals 2020,10, 311 8 of 16 Both hydrotalcite and amesite have been the Mg-hydrated phases detected by XRD. Hydrotalcite is a layered double hydroxide phase (LDHs) [ 29 ], whereas amesite is a magnesium aluminosilicate hydrate phase (M-A-S-H). To confirm the presence of the Mg-hydrated phases detected by XRD, the binder fraction <2 µ m of Samples CA-AL-2 (vault mortar) and CA-AL-9 (tank mortar) were analysed by thermogravimetric analysis (TGA). The TGA results are shown in Figure 6. Figure 6. Thermogravimetric analyses of the binder fraction <2 µ m from the vault mortar (Sample CA-AL-2 in black) and tank mortar (Sample CA-AL-9 in green). Sample CA-AL-2 shows a total weight loss of 38.14%, whereas Sample CA-AL-9 shows a total weight loss of 28.17%. Since the total weight loss of pure calcium carbonate is 44%, these lower weight losses indicate the presence of other mineral phases in the binder as indicated by the XRD results (Figure 5). The TGA curves show four main weight loss regions. The first weight loss (<120  C) and the second weight loss (120 to 200  C) are attributed to the adsorption water and poorly bonded interlayer water, respectively. The third weight loss (200 to 600  C) is attributed to dehydration caused by the loss of hydroxyl groups (OH  ). The last fourth weight loss (600 to 800  C) is related to the decomposition of the carbonates [ 30 – 32 ]. No weight loss is observed over 800  C. Considering the DSC curve, between 200 and 600  C, two endothermic peaks are observed in both Sample CA-AL-2 and Sample CA-AL-9. These two endothermic peaks correspond to the hydrotalcite (LDHs), which decomposes in two steps in this range of temperatures [ 33 , 34 ]. Nevertheless, the second endothermic peak between 450 and 600  C can also be related to the decomposition of the amesite (M-A-S-H) and illite-like phyllosilicates [ 35 – 38 ] present in Sample CA-AL-9, and therefore, they appear to overlap. Between 800 and 900  C, an endothermic peak is only detected in Sample CA-AL-9, confirming the presence of amesite and illite in the tank mortar sample, since the breakdown of both phases takes place in this temperature range [35–37]. X-ray fluorescence was performed to determine the chemical composition of the binder fraction <2 µ m of Samples CA-AL-2 and CA-AL-9. Chemical results of both vault and tank mortars (Samples CA-AL-2 and CA-AL-9, respectively) were used to calculate the Hydraulicity Index (HI) and Cementation Index (CI) in order to assess and compare the hydraulicity degree of binders from the vault and tank (Table 2). Hydraulicity is classified as weak (HI =0.1–0.2, CI =0.3–0.5), moderate (HI =0.2–0.4, CI =0.5–0.7), and eminent (HI <0.4, CI =0.7–1.1) [ 24 , 25 ]. According to the HI and CI values, the mortar binder from the cistern tank is eminently hydraulic, whereas the mortar binder from the vault is weakly hydraulic. Applied Mineralogy in the Study of Historical Lime Mortars 190 Minerals 2020,10, 311 9 of 16 Table 2. Semiquantitative results of the major elements of the binder fraction <2 µ m in powder samples from the lunette of the barrel vault and tank samples determined by X-ray fluorescence, the hydraulicity index (HI), and the cementation index (CI). Chemical results are expressed as oxides in wt%. Iron content is expressed as total Fe2O3t. LOI: loss on ignition (%). Sample Structure MgO Al2O3SiO2K2O CaO TiO2MnO Fe2O3t LOI HI CI CA-AL-2 Lunette 6.16 2.43 5.55 0.23 44.73 0.20 0.05 2.40 38.14 0.20 0.37 CA-AL-9 Tank 6.70 8.15 21.12 1.08 29.20 0.35 0.15 4.88 28.17 0.95 1.85 4.2. Study of the Pigmented Layer of Plaster Scanningelectronmicroscopy(SEM)wasperformedonSampleCA-AL-1forbettercharacterization of the plaster. SEM observations show that the pigmented layer of plaster is less porous than the inner layer and that the contact surface between both layers is rough (Figure 7). Figure 7. SEM image of the cistern plaster. A: pigmented layer; B: inner layer. Rough contact surface in red. The outermost pigmented layer of the plaster was also analysed by Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) in order to determine whether any other type of additive was used in the manufacture. Raman spectroscopy confirmed that the pigmented layer of plaster is mainly composed of a mixture of calcite and hematite (Figure 8a). Raman spectra show intense bands at 282 cm 1 , 712 cm 1 , and 1087 cm 1 attributed to calcite and less intense bands at 226 cm 1 , 294 cm 1 , and 410 cm 1 attributed to hematite [ 39 , 40 ]. Broad bands at 355 and 464 cm 1 related to quartz are also observed. The broad band identified in the region of 1150–1450 cm 1 is attributed to an organic compound, but due to the low quality of the spectrum, it was difficult to identify (Figure 8b). Infrared spectroscopy (FTIR) analysis was performed in order to identify the organic compound detected by Raman spectroscopy. FTIR spectra show bands at 2864 cm 1 , 2514 cm 1 , 1794 cm 1 , 1428 cm 1 , 871 cm 1 , and 711 cm 1 attributed to calcite and bands at 1027 cm 1 , 642 cm 1 and 528 cm 1 attributed to the hematite (red earth pigment) (Figure 9a) [ 41 – 43 ]. Nevertheless, the strong absorption of the inorganic phases hides the signal of the organic compound, hindering its identification. To improve the FTIR signal of the organic component, an extraction was conducted using 200 µ L of dichloromethane. The resulted supernatant was evaporated on a potassium bromide disk to be then analysed. The intense bands detected at 2955 cm 1 , 2916 cm 1 , 2848 cm 1 , 1736 cm 1 , and 1472 cm 1 were attributed to beeswax organic compound (Figure 9b) [43]. 8. Appendices: Published and Submitted Works 191 Minerals 2020,10, 311 10 of 16 Figure 8. Raman spectroscopy of the bulk fraction of the pigmented layer of the cistern plaster. ( a ) Raman spectra showing the highest intensities bands of calcite, hematite, and quartz. ( b ) Raman spectra showing an organic compound in the region of 1150–1450 cm 1 . Calcite bands at 282 cm 1 , 712 cm 1 , and 1087 cm 1 ; hematite bands at 226 cm 1 , 294 cm 1 , and 410 cm 1 ; quartz bands at 355 cm1and 464 cm1. Figure 9. Fourier transform infrared spectroscopy (FTIR) analysis of the pigmented layer of the cistern plaster. ( a ) FTIR spectra showing the highest intensities bands of calcite and hematite (red earth). ( b ) FTIR spectra showing the highest intensities bands of the organic compound identified as beeswax. Calcite bands at 2864 cm 1 , 2514 cm 1 , 1794 cm 1 , 1428 cm 1 , 871 cm 1 , and 711 cm 1 ; hematite (red earth) bands at 1027 cm 1 , 642 cm 1 , and 528 cm 1 . Beeswax bands at 2955 cm 1 , 2916 cm 1 , 2848 cm 1 , 1736 cm1, and 1472 cm1. 5. Discussion Petrologicalstudysuggestsacarefulprocessinboththemortarmanufactureandmortarapplication technique for the cistern construction according to the specific characteristics needed for this structure. The impermeability of the cistern tank is an essential requirement for appropriate water storage. Mortar impermeability is strictly related to mortar hydraulicity, which is favoured by the use of silico-aluminous aggregates working as reactive materials in the mixture [ 8 , 10 – 13 ]. The use of silico-aluminous rocks and ceramic fragments as aggregates in the tank mortar manufacture, instead of the carbonated aggregates used for the vault mortars, indicates a deliberate selection of aggregates in order to confer hydraulicity to the mortar to obtain waterproof mortars. Furthermore, the use of silico-aluminous aggregates adds greater cohesion and mechanical strength to the mortar [44,45]. The raw materials that were used as aggregates to manufacture both the lime mortars from the vault and cistern tank correspond to the surrounding geological materials. Not only the selection of aggregates was important but also the aggregate sorting. The grain size of aggregates in the Applied Mineralogy in the Study of Historical Lime Mortars 192 Minerals 2020,10, 311 11 of 16 tank mortars becomes smaller and better sorted from the first layer of the structural mortar toward the outermost pigmented layer of the plaster. Besides, aggregate size also contributes to material reactivity, since the smaller the size, the higher the specific surface area and thus the higher the reaction rate [ 8 , 46 – 48 ]. Furthermore, mortar porosity is lower in mortars with better-sorted aggregates since they produce a better-packed system [49–52]. Themineralogical analyses allowed identifying additives in the pigmentedlayer. TheXRD, Raman, and FTIR analyses indicate that hematite was used as an inorganic additive, which led to the reddish colour of the pigmented layer (Figures 5,8and 9). Hematite would not be related to ceramic fragments, since they were not observed either in the petrographic study or by XRD (Figures 4f and 5d). Therefore, the hematite may have been deliberately added. FTIR analyses allowed identifying the beeswax as the organic additive in the pigmented layer (Figure 9). Beeswax was the most common natural wax used as an organic additive to provide impermeability and sealing property to the materials [ 53 ]. Since organic compounds are more susceptible to degradation than inorganic compounds, knowledge of the composition of ancient additives is essential for appropriate interventions on archaeological structures [53,54]. Therefore, to ensure the impermeability of the cistern tank, a multilayer application of di↵erent mortars was performed using silico-aluminous aggregates and decreasing their grain size from the first layer of the structural mortar toward the inner layer and applying a final plaster with a beeswax-bearing pigmented layer (Figure 10). Figure 10. Schematic image of the multilayer application technique for mortars in Amaiur Castle cistern. The cistern tank is shown in green, the vault lunette is shown in blue, the barrel vault is shown in yellow, and the 14th–15th centuries wall is shown in black. Furthermore, the reaction zones observed in dolomitic aggregates resulted from the dedolomitization of dolomitic aggregates, and the presence of hydrotalcite in the binder has been related to the use of the traditional hot-mixing method in mortar manufacture [ 23 ]. In the manufacture of cistern tank mortars, the use of this traditional hot-mixing method would also be expected since reaction zones were not only observed at the edge of the dolomitic aggregates, but they also stand out in the ceramic fragments and some silico-aluminous aggregates (Figure 4a–d). 8. Appendices: Published and Submitted Works 193 Minerals 2020,10, 311 12 of 16 Quartz and phyllosilicates are attributed to the ceramic fragments and silico-aluminous rocks used as aggregates, whereas magnesium calcite, hydrotalcite, and amesite are mineral phases formed during mortar manufacture (Figure 5). Magnesium calcite is formed in the setting of mortar as a result of the lime cycle [ 24 , 55 ], and hydrotalcite is a carbonated mineral formed during the slaking process in the presence of available magnesium content [28]. Hydrotalcite has been identified in all analysed mortar binders (Figure 5). Magnesium released from the dedolomitization process, leading to the formation of the reaction zone in the edge of dolomitic aggregates, and the aluminium released from the breakdown of phyllosilicates favours the formation of hydrotalcite [ 23 , 56 – 58 ]. Nevertheless, some amount of magnesium and aluminium can also come from the lime used for the mortar manufacture when impure limestones or partially dolomitized limestones have been used as the raw material for lime production [ 28 , 59 ]. Therefore, the presence of hydrotalcite and the absence of dolomitic aggregates in the pigmented layer of plaster (Figures 4and 5) would indicate the use of impure limestones or partially dolomitized limestones for the production of lime for the cistern construction. The aluminosilicate phases present in the silico-aluminous aggregates of the tank mortars are highly reactive materials that in the presence of alkalis react with water, forming a wide family of hydration products that induce hydraulic properties to the mortars [ 8 , 15 , 46 ]. Reaction zones observed in the edge of the silico-aluminous aggregates suggest the development of this reaction (Figure 4b–d). The reaction between aluminosilicate phases and an alkaline solution is known as an alkali-silicate reaction (ASSR), which is a specific type of alkali-silica reaction (ASR) [60–62]. Amesite has been the only aluminosilicate hydrated phase detected in the tank mortars. This mineral phase has also been described in some mortars with pozzolanic aggregates [ 48 , 63 ]. Amesite is a magnesium aluminosilicate hydrate (M-A-S-H) phase, and although it is chemically related to chlorites, it displays a similar structure to serpentine with alternating tetrahedral and trioctahedral layers [ 37 ]. The amesite has only been detected in samples containing silico-aluminous aggregates, indicating that it would have formed as a result of the reaction between the aluminosilicate phases and the putty alkalis. Magnesium silicate hydrate (M-S-H) phases have been described during the hydration of MgO-bearing lime materials and formed by the reaction between magnesium and silicate ions [ 64 – 66 ]. TheM-S-Hphasesshowalayeredstructureandhavebeenrelatedtopoorlycrystallinephyllosilicates[ 64 , 66 – 69 ]. The reaction zone of the dolomitic aggregates of the structural mortars from Amaiur Castle showed the presence of M-S-H phases, which are suggested as a result of an ASSR, although the presence of the M-S-H phases could not be confirmed [ 23 ]. According to Mackenzie and Bowden [ 37 ], amesite is formed by the substitution of the Si 4+ in the tetrahedral layers and the Mg 2+ in the octahedral layers by the Al 3+ . Therefore, the amesite detected in the mortars from the cistern tank could also have been formed as a result of the ASSR, since the kinetic formation of M-A-S-H phases has been described as similar to M-S-H phases, incorporating aluminium into the structure [63,70]. Besides, the phases formed as a result of the reaction between the aluminosilicate phases of the silico-aluminous aggregates and the putty alkalis contribute to decreasing the porosity and therefore favour the waterproofing of the cistern tank [45,71–73]. The study of both structural and plaster mortars from Amaiur Castle cistern show patterns/rules in the mortar manufacture according to the specific construction requirements, distinguishing two kinds of mortars with aggregates of di↵erent nature. Mortars from the cistern tank acquired hydraulicity by the addition of silico-aluminous rocks and ceramic fragments as aggregates. 6. Conclusions The study of the mortars from the Amaiur Castle cistern has allowed assessing the knowledge of the mortar manufacturing process and the mortar application techniques to ensure the structure waterproofing necessary for the correct storage of water. Applied Mineralogy in the Study of Historical Lime Mortars 194 Minerals 2020,10, 311 13 of 16 The cistern shows three types of lime mortars with di↵erent compositional characteristics related to the specific function within the structure: structural mortars from the barrel vault, structural mortars from the tank, and plaster. The nature of the aggregates used in the manufacture of cistern mortars was di↵erent, according to specific construction requirements. Carbonated aggregates were used in the vault mortar and silicious and silico-aluminous aggregates in the tank mortars and plaster, suggesting the specific selection of raw materials. The raw materials of the surrounding geological materials were used for the manufacture of the lime mortars of the cistern of the Amaiur Castle. To confer hydraulicity to the mortars of the cistern tank and achieve the waterproofing of the structure, ceramic fragments and silico-aluminous rocks were used as aggregates in the manufacture. Besides, the reaction zones on the edge of silico-aluminous rocks and ceramic aggregates resulted from an alkali silicate reaction (ASSR) that favoured the formation of amesite, the magnesium aluminosilicate hydrated (M-A-S-H) phase detected in the binder of the tank mortars. A multilayering application technique was performed in the construction of the cistern tank. Two/three layers have been di↵erentiated in the structural mortar from the tank, with a decrease in grain size and an improvement in sorting of aggregates from the inner part to the outer part. The plaster is formed by two layers: an inner layer and an outer pigmented layer. The pigmented layer of plaster is composed by two types of additives. Hematite was identified as an inorganic additive giving rise to the reddish colour of the layer. Additionally, beeswax was identified as an organic additive used to confer impermeability to the pigmented layer. The presence of hydrotalcite and the absence of dolomitic aggregates in the pigmented layer point to the use of impure limestones or partially dolomitized limestones as the raw material for the production of lime at Amaiur Castle. Author Contributions: Conceptualization, G.P.-A., M.C.Z. and L.A.O.; Data Curation, G.P.-A. and M.C.Z.; Writing—Original Draft Preparation, G.P.-A.; Writing—Review and Editing, G.P.-A., M.C.Z.; Funding Acquisition, L.A.O. and J.A.M. All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by the IT1193-13 project of the Basque Government. Acknowledgments: G.P.-A. acknowledges the PhD research grant of the Basque Government 2015-1-02-35. The authors would like to thank Peter Smith for reviewing the use of English in the manuscript. Conflicts of Interest: The authors declare no conflict of interest. References 1. Cadogan, G. Water management in Minoan Crete, Greece: The two cisterns of one Middle Bronze Age settlement. Water Sci. Technol. Water Supply 2007,7, 103–112. [CrossRef] 2. Angelakis, A.N.; Spyridakis, D.S. Water supply and wastewater management aspects in Ancient Greece. Water Sci. Technol. Water Supply 2010,10, 618–628. [CrossRef] 3. Angelakis, A.N.; Mays, L.W.; Koutsoyiannis, D.; Mamassis, N. Evolution of Water Supply through the Millennia; IWA Publishing: London, UK, 2012. 4. Carrion,A.; Formnes,A. Undergroundmedieval waterdistribution networkin a Spanishtown. Tunn. Undergr. Space Technol. 2016,51, 90–97. [CrossRef] 5. Mays, L.; Antoniou, G.P.; Angelakis, A.N. History of Water Cisterns: Legacies and Lessons. Water 2013 ,5, 1916–1940. [CrossRef] 6. Van Hees, R.P.J.; Binda, L.; Papayianni, I.; Toumbakari, E. Characterisation and damage analysis of old mortars. Mater. Struct. 2004,37, 644–648. [CrossRef] 7. Stefanidou, M.; Pachta, V.; Konopissi, S.; Karkadelidou, F.; Papayianni, I. Analysis and characterization of hydraulic mortars from ancient cisterns and baths in Greece. Mater. Struct. 2014,47, 571–580. [CrossRef] 8. Rizzo, G.; Ercoli, L.; Megna, B.; Parlapiano, M. Characterization of mortars from ancient and traditional water supply systems in Sicily. J. Therm. Anal. Calorim. 2008,92, 323–330. [CrossRef] 8. Appendices: Published and Submitted Works 195 Minerals 2020,10, 311 14 of 16 9. Henry, A.; Stewart, J. Practical Building Conservation: Mortars, Renders & Plasters; Practical Building Conservation Series; English Heritage: Surrey, UK, 2011. 10. Baronio, G.; Binda, L. Study of the pozzolanicity of some bricks and clays. Constr. Build. Mater. 1997 ,11, 41–46. [CrossRef] 11. Baronio, G.; Binda, L.; Lombardini, N. The role of brick pebbles and dust in conglomerates based on hydrated lime and crushed bricks. Constr. Build. Mater. 1997,11, 33–40. [CrossRef] 12. Stefanidou, M.; Papayianni, I. The role of aggregates on the structure and properties of lime mortars. Cem. Concr. Compos. 2005,27, 914–919. [CrossRef] 13. Arizzi, A.; Cultrone, G. Aerial lime-based mortars blended with a pozzolanic additive and di↵erent admixtures: A mineralogical, textural and physical-mechanical study. Constr. Build. Mater. 2012 ,31, 135–143. [CrossRef] 14. Miriello, D.; Bloise, A.; Crisci, G.M.; De Luca, R.; De Nigris, B.; Martellone, A.; Osannac, M.; Paced, R.; Peccia, A.; Ruggieri, N. New compositional data on ancient mortars and plasters from Pompeii (Campania-Southern Italy): Archaeometric results and considerations about their time evolution. Mater. Charact. 2018,146, 189–203. [CrossRef] 15. Walker, R.; Pav í a, S. Physical properties and reactivity of pozzolans, and their influence on the properties of lime–pozzolan pastes. Mater. Struct. 2011,44, 1139–1150. [CrossRef] 16. Bonazza, A.; Ciantelli, C.; Sardella, A.; Pecchioni, E.; Favoni, O.; Natali, I.; Sabbioni, C. Characterization of hydraulic mortars from archaeological complexes in Petra. Period. Mineral. 2014,82, 459. 17. Rampazzi, L.; Colombini, M.P.; Conti, C.; Corti, C.; Lluveras-Tenorio, A.; Sansonetti, A.; Zanaboni, M. Technology of medieval mortars: An investigation into the use of organic additives. Archaeometry 2016 ,58, 115–130. [CrossRef] 18. Gal á nP é rez, E.; Garc í a de Domingo, A.; Cabra Gil, A.; Ganz á lez Lastra, J.; Matinez Torres, L.M.; Pesquera P é rez, A. Memoria Hoja 66-III (Maya de Bazt á n). In Mapa Geol ó gico de Navarra. E. 1:25000; Diputación Foral de Navarra: Navarra, Spain, 2002. 19. Juch, D.; Krausse, H.F.; Müller, D.; Requadt, H.; Schafer, D.; Sole, J.; Villalobos, L. Memoria Hoja 66 (Maya del Baztan). In Mapa Geol ó gico de España, E. 1:50.000, 1st ed.; Segunda Serie; MAGNA: Magna Drive Aurora, ON, Canada, 1974. 20. AGN. Royal and General Archive of Navarre. In Rena Papers; 15/3, 52, Box 33055: 1516; Government of Navarre: Pamplona, Spain, 1995. 21. Sagredo, I. El castillo de Amaiur a Trav é s de la Historia de Navarra; Editorial Pamiela Argitaletxea: Pamplona, Spain, 2009. 22. Sagredo, I. Navarra. In Castillos que Defendieron el Reino (Tomo I) de Laguardia a Foix, y del Moncayo al Goierri; Editorial Pamiela Argitaletxea: Pamplona, Spain, 2006. 23. Ponce-Ant ó n, G.; Zuluaga, M.C.; Ortega, L.A.; Mauleon, J.A. Multi-analytical approach for chemical-mineralogical characterization of reaction rims in the lime mortars from Amaiur Castle (Navarre, Spain). Microchem. J. 2020,152, 104303. [CrossRef] 24. Boynton, R.S. Chemistry and Technology of Lime and Limestone; John Wiley & Sons, Inc.: New York, NY, USA, 1980. 25. Vicat, L.J. Mortars and Cements; Donhead Publishing: Shaftesbury, UK, 1997. 26. Folk, R.L. A comparison chart for visual percentage estimation. J. Sediment. Res. 1951,21, 32–33. 27. Ortega, L.A.; Zuluaga, M.C.; Alonso-Olazabal, A.; Murelaga, X.; Insausti, M.; Ibañez-Etxeberria, A. Historic lime-mortar 14C dating of Santa Mar í a la Real (Zarautz, northern Spain): Extraction of suitable grain size for reliable 14C dating. Radiocarbon 2012,54, 23–36. [CrossRef] 28. Ponce-Ant ó n, G.; Ortega, L.A.; Zuluaga, M.C.; Alonso-Olazabal, A.; Solaun, J.L. Hydrotalcite and Hydrocalumite in Mortar Binders from the Medieval Castle of Portilla ( Á lava, North Spain): Accurate Mineralogical Control to Achieve More Reliable Chronological Ages. Minerals 2018,8, 326. [CrossRef] 29. Mills,S.J.; Christy,A.G.; G é nin,J.-M.R.; Kameda, T.; Colombo,F. Nomenclatureofthehydrotalcitesupergroup: Natural layered double hydroxides. Mineral. Mag. 2012,76, 1289–1336. [CrossRef] 30. Bakolas, A.; Biscontin, G.; Moropoulou, A.; Zendri, E. Characterization of structural byzantine mortars by thermogravimetric analysis. Thermochim. Acta 1998,321, 151–160. [CrossRef] 31. Paama, L.; Pitkänen, I.; Rönkkömäki, H.; Perämäki, P. Thermal and infrared spectroscopic characterization of historical mortars. Thermochim. Acta 1998,320, 127–133. [CrossRef] Applied Mineralogy in the Study of Historical Lime Mortars 196 Bottom right, masons manufacturing a mortar. A detail from Construction du Temple de Jérusalem par ordre de Salomon., In: Antiquités judaïques de Flavius Josèphe. Bibliothèque Nationale de France, Paris. Ms 247, fol.163 v. Jean Fouquet, 1470-1475. This PhD thesis has been accomplished with the research grant from the Basque Country Government PRE-2015-1-0235 in the Department of Mineralogy and Petrology of the University of the Basque Country (UPV/EHU) under the supervision of Dr Maria Cruz Zuluaga and Dr Luis Angel Ortega. The conservation and restoration of monuments must have recourse to all the sciences and techniques which can contribute to the study and safeguarding of the architectural heritage. Article 2. Venice Charter, 1964