Influence of moisture content on the mechanical properties of an ancient high-porosity building sandstone: San Cristóbal's stone (Andalusia, Spain)

Case Studies in Construction Materials 18 (2023) e02128 Available online 10 May 2023 2214-5095/© 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Influence of moisture content on the mechanical properties of an ancient high-porosity building sandstone: San Crist´ obal’s stone (Andalusia, Spain) Juan Ram´ on Baeza a , Víctor Comp´ an b , * , Pablo Pach´ on b , Jaime Aguilar b , Margarita C´ amara b a Department of Architectural Construction II, University of Seville, Seville, Spain b Department of Building Structures and Ground Engineering, University of Seville, Seville, Spain ARTICLE INFO Keywords: Sandstones Building stone Moisture content Mechanical properties Static elastic modulus Dynamic elastic modulus Uniaxial compressive strength Empirical relationships ABSTRACT San Crist´ obal’s is a porous sandstone that is present in masonry structures of numerous historical buildings located in the southwest of Spain (15 th –18 th centuries). In order to guarantee conservation and structural integrity, most of these structures have been assessed during the last two decades after they presented severe damages in locations affected by moisture. In this study, static and dynamic elastic modulus and uniaxial compressive strength of San Crist´ obal’s stone are determined in the laboratory under dry and saturated states, as well as with a moisture content of 40%, to establish the influence of moisture on them. An experimental campaign was conducted on 16 samples of ancient stone, extracted from the core of structural walls and columns during a structural intervention. The results show how the moisture content directly affects the deformability of the stone, especially between dry and 40% moisture content states. The values of the elastic modulus, both static and dynamic, are reduced with average values of 16.98% and 22.85% respectively. The loss of uniaxial compressive strength between the dry and saturated states is established with a mean value of 29.82%. Additionally, empirical relationships between the studied mechanical properties have been developed, reaching coefficients of determination over 0.90 in most cases. 1. Introduction Stone masonries are widespread as part of historical buildings, so they are usually under heritage protection criteria. This implies not only that they are needed to be conserved but also the responsibility of guaranteeing their structural integrity, especially when they are part of buildings that are still used. [1,2]. It is widely known that the mechanical properties of natural stones used as building structural materials are negatively affected by moisture [3]. Stone masonries in historical structures are on the outside, so they are subjected to environmental humidity changes. In addition, the structural elements that are in contact with the ground can reach higher moisture levels because of capillarity. Due to structural assessments of historical buildings require a deep knowledge about the mechanical properties of the material, it is important to know the influence of moisture on the mechanical behavior of these natural stones to ensure adequate safety levels. In this * Corresponding author. E-mail address: [email protected] (V. Comp´ an). Contents lists available at ScienceDirect Case Studies in Construction Materials journal homepage: www.elsevier.com/locate/cscm https://doi.org/10.1016/j.cscm.2023.e02128 Received 19 February 2023; Received in revised form 2 May 2023; Accepted 6 May 2023 Case Studies in Construction Materials 18 (2023) e02128 2 sense, and in order to be respectful and consistent with the character of protection of this kind of structures, non-destructive techniques to obtain or predict mechanical properties would be especially interesting [4,5]. These techniques would increase their practical applicability, because they could be performed in situ in addition to in laboratory and data could be taken on numerous areas of the building, that is, more extensively than if it depended on the extraction of drilling specimens to be tested in laboratory [6]. Among the different non-destructive tests (NDT), the following stand out: Schmidt hammer, to obtain compressive strength from rebound number [7] and methods based on wave propagation, through which mechanical properties such as elastic modulus and uniaxial compressive strength can be predicted [8]. Several authors have established empirical relationships between P-wave velocity and elastic modulus [8] in sedimentary rocks and between P-wave velocity and uniaxial compressive strength [9] in squeezing rocks, both cases in a dry state. In addition, p-wave velocity is sensitive to water saturation [10], which allowed Karakul [11] to propose an empirical relationship between uniaxial compressive strength and P-wave velocity of several types of rocks at different degrees of saturation. In this case, and in order to improve the coefficient of determination of proposed equations, the percentage of clay minerals of the stone was considered as independent variable, due to it contributes to a decrease in mechanical properties after its interaction with water. Likewise, there are also methods that allow obtaining in situ moisture content of the stone. The most common measurements are electrical-based methods. Moisture content can be obtained from electrical resistance or capacitance of the stone [12]. The existence of this kind of technique, which can be performed in situ, makes it useful to count on empirical relationships through which the mechanical behavior of historical stone masonries could be predicted from measurements experimentally obtained. San Crist´ obal’s stone can be found in numerous historic buildings located in the western area of Andalusia (Spain) between the 15 th –18 th centuries. This mainly includes religious buildings, as well as civil and military ones. The Cathedral (1434) and the Monastery of San Jer´ onimo (1414), both in Seville [13,14]; Santiago Church (15 th century) and San Dionisio Church (15 th century), both in C´ adiz [15,16], are some examples where San Crist´ obal’s stone has been used. During the last two decades, several of these buildings have been subjected to structural assessments after they presented severe damages that compromised their structural integrity. Thus, for examples, (i) two columns of the Cathedral of Seville needed to be replaced due to the decrease of their mechanical properties; (ii) Santiago Church presented instability problems because of the same reason and (iii) severe cracks appeared along the main cloister of the Monastery of San Jer´ onimo after an architectural intervention, especially in areas affected by moisture. Fig. 1 shows severe damages on one of the columns of Monastery of San Jer´ onimo (in Seville-Spain), where moisture content over 50% was identified [6]. In order to conduct structural assessments that ensure the structural integrity of the wide Andalusian built heritage made using San Crist´ obal’s stone, it is necessary to have a deep knowledge of the material. This sandstone is characterized by a low bulk density (1710–1860 kg/m 3 ) [15,17] and a high porosity (22.4–27%) [15,17]. Regarding their main mechanical properties, compressive strength has been established between 1.5 and 2.6 MPa [15], and elastic modulus is between 4000 and 10,000 MPa [15,17]. Other authors have studied the effect of moisture content on mechanical properties of different sandstones. C.G. Dyke and L. Dobereiner [18], tested nine specimens from three different sandstones under dry and saturated states, as well as three intermediate moisture content (32%, 63% and 96%). It was found that moisture content could change mechanical behavior of the sandstones signtificantly, reducing the elastic range of the material, which was often below 20% of peak strength in saturated conditions; A. B. Hawkins [19] presented a studies that included thirty five different sandstones from 21 British localities. In this case, some of the sandstones presented a significant decrease in uniaxial compressive strength from dry to saturated states. The loss of strength was established between 8.2% and 78.1% and a similar effect was observed on the elastic modulus. More recent studies of the influence of moisture content on the mechanical properties of sandstones, like those performed by A. Shakoor (2009) [20], E. Verstrynge (2014) [3] and E. Kim (2016) [21] show results that lead to the same conclusions about the effect of Fig. 1. Severe damages on columns of the Monastery of San Jeronimo (Seville - Spain) affected by moisture [6]. J.R. Baeza et al. Case Studies in Construction Materials 18 (2023) e02128 3 moisture content, although with different extent, depending on the specific stone. Shakoor [20] analyzed 8 types of stones with 18 specimens, obtaining a general range of unconfined compressive strength (UCS) reduction between 20% and 40% in dry and saturated states and reaching in two types of sandstones a strength decrease of 62.6% and 71.6% respectively. In this last work, some equations were defined to predict UCS from square roots of the degree of saturation. However, none of the 8 stones analyzed present physical properties close to those that characterize San Crist´ obal’s stone, with lower density and higher porosity. On the other hand, the study conducted by Kim [21] affirmed that the sandstones he analyzed reduced their compressive strength by approximately 20% from dry to saturated states. In this case, despite one of the sandstones studied by Kim (Buff sandstone) presented a porosity (22.7%) close to the range of San Crist´ obal’s stone and he studied several samples, no other of the physical properties of Buff sandstone are shown, so it is difficult to assess the correspondence between Buff and San Crist´ obal’s stones. Among these studies, the work by Verstrynge [3] is pointed out not only because it includes the analysis of the influence of moisture content on mechanical properties of a sandstone, but also because it is an aging sandstone from a bell tower (17 th century) that collapsed in Meldert (Belgium, 2006). The main physical properties of this sandstone (Diestian) are similar to those presented by San Crist´ obal’s stone, that is, a density of about 1800 kg/m 3 and a 22–27% porosity. However, their mineralogical composition differs. Diestian sandstone is mainly characterized by about 60% of quartz and 24% of glauconite [Verstringe, 2014], while San Crist´ obal’s stone contains 60% of calcium carbonate and around the 35% of quartz [22]. For the case of Diestian sandstone, Verstringe obtained a decrease of UCS within the range 40–59% considering dry and saturated states. The novelty of this work lies on its study object, aging San Crist´ obal’s stone, the construction material of numerous and important historical buildings in the southwest of Spain. The mechanical properties of this natural stone have never been studied before under different moisture conditions, even though the affection of moisture on them seems to be evident because of damages such as those shown in Fig. 1. The objective is to determine how moisture affects this stone regarding both the deformability, through the elastic modulus, and the compressive strength. Static and dynamic elastic modulus have been distinct in order to consider the corresponding main roles of each one of them in structural assessments of historical constructions, that is, the static elastic modulus is useful to develop numerical models which structural analyses can be based on, and dynamic elastic modulus is easily and extensively determined in situ by implementing non-destructive techniques that use wave propagation. On the other hand, and as a secondary aim, correlations between the parameters will be addressed under different moisture levels. To reach the described objectives, different tests have been conducted in laboratory on 16 San Crist´ obal’s stone specimens. Physical properties (density, porosity and absorption) and mechanical properties (static and dynamic elastic modulus and uniaxial compressive strength) of each one of the specimens were obtained through an experimental campaign considering different moisture contents. These specimens were extracted from the core of some columns and walls of Santiago Church, in Jerez de la Frontera (C´ adiz - Spain) (15 th century), during structural consolidation works that took place in 2007. Although, this implies a limitation of the work regarding the reduced number of specimens studied, this also constitutes a unique opportunity because it allows not only to count on specimens of the mentioned stone (they could have been extracted from the corresponding quarry) but also to study aging stone, as ancient as that to be assessed in any structural analysis that could be conducted on built heritage made up of San Crist´ obal’s stone. 2. Experimental program To reach the proposed aims, experimental tests were performed in laboratory on 16 specimens which are described in section 2.1. Section 2.2. details the series of tests that have been performed. They were conducted to obtain elastic moduli, both static and dynamic, and uniaxial compressive strength. These three mechanical properties were determined for different moisture contents, so section 2.2 includes the description of the procedures followed to control moisture in specimens as well. On other hand, and due to the main role of moisture content in this study, the absorption of the specimens was also determined to characterize them by this parameter. Regarding the different moisture contents that have been considered for the specimens to be analyzed, elastic moduli were determined for three moisture contents: dry and saturated states and 40%. The consideration of this intermediate moisture value responds mainly to two reasons: (i) a preliminary study carried out by authors established that the higher loss of mechanical capacity Fig. 2. Cylindrical specimens extracted from columns and walls of Santiago Church (Jerez de la Frontera, Cadiz - Spain). J.R. Baeza et al. Case Studies in Construction Materials 18 (2023) e02128 4 takes place between dry and 40% in San Crist´ obal’s stone [23]; (ii) Moisture contents reaching the values in this range have been recognized in situ in structural elements made up of San Crist´ obal’s stone [6]. Uniaxial compressive strength has been analyzed considering dry and saturated states, as a reference of the limit states. 2.1. Material and samples The specimens that have been analyzed are cylindrical and were extracted by drilling from columns and walls of Santiago Church in Jerez de la Frontera (C´ adiz - Spain), during consolidation works (Fig. 2). Jerez de la Frontera has a warm Mediterranean climate, environmentally characterized by mean values of 17,75 degrees of temperature, 68,06% humidity and 524 mm of annual rainfall (mean values of the last 20 years)[24]. The extraction of the specimens was performed from the top of some of the columns and walls of the church and along their main load direction, that is, the longitudinal direction of both the specimens and the structural elements correspond (Fig. 3). Table 1 shows the location and dimensions of each one of the 16 specimens. They present different dimensions because of the way of drilling stone from structural elements. However, all of them comply with the conditions established by the standards that have been taken as a basis during the experimental campaign. These specimens were used to determine mechanical and physical properties. The analyzed specimens are dated to the same period as the elements which they were extracted from (late 1 st century and early 16 th century). The stone of Santiago Church was obtained from the quarry of San Crist´ obal in the basin of Guadalete River, SW Andalucía. This is a chalcitic sandstone that is mainly composed of CaCO3 (67%) and SiO2 (30%) as an average composition. 2.2. Methods 2.2.1. Procedure to control the moisture content of the specimens Dry state was reached through the application of the EN 1936:2006 standard [25]. Saturated state was achieved after having specimens submerged for 24 h. After getting the 100% of water contain, specimens experimented with a controlled loss of moisture in the oven until their weight denoted a moisture content of 40% considering the difference in weights between dry and saturated states. 2.2.2. Physical properties: absorption, bulk density and porosity Absorption. Standard EN 13755:2008 [26] was followed. This standard contains a method to determine the absorption of water by natural stone through water immersion at atmospheric pressure. The studied specimens comply with the geometric requirements of this standard, that is, mínimum apparent volume of 60 ml and a ratio of superficial area to volume within the range 0.08–0.20 mm −1 . Absorption is the ratio of the difference between the masses of a specimen in saturated and dried state to the mass of the dried one. Porosity and bulk density. Standard EN 1936:2006 [25] was followed. This standard define density as the ratio of the weight of the dried specimen to its bulk volume. On the other hand, it defines porosity as the ratio of the volume of OPEN pores to the bulk volume of the specimen. Fig. 3. Location of analyzed specimens from Santiago Church (Jerez de la Frontera, Cadiz - Spain). J.R. Baeza et al. Case Studies in Construction Materials 18 (2023) e02128 5 2.2.3. Dynamic elastic modulus (E dyn ) Standard EN 14146:2004 [27] was followed to determine the dynamic elastic modulus (E dyn ) by means of sonic waves tests (Fig. 4). According to this standard [27], E dyn can be obtained from the bulk density and the fundamental resonance frequency. 2.2.4. Static elastic modulus (E st ) and uniaxial compressive strength (UCS) Standard EN 14580:2006 [28] was followed to determinate Static elastic modulus (E st ). Standard EN 1926:2006 [29] was applied to obtain uniaxial compressive strength (UCS). In both cases, an MTS Criterion Electromechanical Test System whose load capacity is of 100 KN (C45.105) was used to perform the corresponding mechanical tests (Fig. 5). Strains were measured through a device of National Instruments (cDAQ-9174, NI-9219) in addition to LVDTs Solartron AXR/2.5/S. MTS TestSuite TW and Signal Express 2015 softwares controlled load cycles and LVDTs deformation respectively [17]. 3. Results and discussion 3.1. Physical properties Table 2 shows the obtained results with respect to physical properties, specifically bulk density, open porosity, and absorption. Likewise, the mean and standard deviation values of each are shown. The bulk density are between 1655 and 1867 kg/m 3 with a mean value of 1776 kg/m 3 , values close to those established by other authors [6,15]. However, porosity and absorption are higher than expected, with mean values of 33.77% and 17.04% respectively. By analyzing results from a statistical point of view, normal results were obtained in the case of bulk density and porosity. Results of absorption are close to normality, with 62.5% of specimens within Mean ±2 SD. Fig. 6 shows Pareto diagrams of the physical properties studied to better describe the obtained ranges of resulting values. A linear relationship between density and porosity had previously been found by the authors [17]. In the case of porosity and absorption, a linear relationship between them is clearly found considering 11 of the 16 specimens studied (Fig. 7), but the remaining specimens, which present similar values for porosity, showed corresponding values for absorptions also very similar. Table 1 Location and dimmensions of analyzed specimens from Santiago Church. Specimen Extraction Depth of ext. (m) Length (mm) Diameter (mm) Length/diameter N01 2 11.20 164 63 2.6 N02 2 19.27 165 69 2.4 N03 5 5.15 215 83 2.6 N04 6 2.18 183 82 2.2 N05 6 4.60 168 83 2.0 N06 6 6.80 194 83 2.3 N07 6 9.27 180 82 2.2 N08 6 11.55 204 83 2.5 N09 6 12.85 202 83 2.4 N10 6 21.21 144 71 2.0 N11 6 22.03 159 71 2.2 N12 A 9.75 131 58 2.3 N13 B 11.26 149 61 2.4 N14 C 21.59 156 61 2.6 N15 D 1.60 155 62 2.5 N17 E 2.67 149 62 2.4 Fig. 4. Test performed to obtain the dynamic elastic modulus. J.R. Baeza et al. Case Studies in Construction Materials 18 (2023) e02128 6 Fig. 5. Tests performed to determine (a) the static elastic modulus and (b) the uniaxial compressive strength. Table 2 Physical parameters obtained from tests in lab [17]. Specimen (Sp) Bulk density (Kg/m 3 ) Porosity (%) Absorption (%) N01 1760.75 34.49 19.63 N02 1843.26 29.58 16.08 N03 1759.05 34.73 19.78 N04 1742.76 35.08 13.90 N05 1831.65 31.65 17.31 N06 1693.98 36.97 21.87 N07 1777.66 33.88 12.83 N08 1655.74 38.66 23.40 N09 1867.62 30.75 16.50 N10 1766.65 34.08 12.50 N11 1791.88 33.03 12.52 N12 1761.35 34.30 19.51 N13 1752.66 34.50 19.73 N14 1798.32 33.11 18.45 N15 1753.07 34.83 12.14 N17 1861.19 30.68 16.52 Mean 1776,09 33.77 17.04 SD 56.69 2.32 3.53 Fig. 6. Physical properties of San Cristobal’s stone: Pareto diagrams. J.R. Baeza et al. Case Studies in Construction Materials 18 (2023) e02128 7 3.2. Deformability (Static (E st ) and Dynamic (E dyn ) elastic modulus) Table 3 shows the static elastic modulus of stone specimens under different moisture conditions: dry state (E st ), 40% moisture content (E st40 ) and saturated state (E st100 ). The variation percentages beween them, the mean and the standard deviation values are also included. On other hand, Fig. 8 plots E st obtained from the specimens for the studied moisture contents. Values obtained for E st , E st40 and E st100 present an acceptable dispersion, with 11/16 specimens (68.7%) within the range Mean ±SD. The same 11 specimens keep this condition for E st in the three moisture states. As shown in Table 3 and Fig. 8, every specimen presented a higher decrease in E st in the range of 0–40% of moisture content than in the range of 40–100%, except for the specimen N13, presents an especially high loss of E st (22.07%) in the range 40–100%. Likewise, it can be seen that 75% of the studied specimens lost 70% or more of their total loss of E st in the range 0–40% of moisture content. These results can be extended to dynamic elastic modulus, as Table 4 and Fig. 9 show. Thus, the same 11 specimens keep the condition of an acceptable dispersion for E dyn , E dyn40 and E dyn100 . Likewise, the main decrease in dynamic elastic modulus occurs between dry state and 40% of moisture content (Fig. 9). However, this last aspect is more pronounced in the case of E dyn than in the case of E st , with a mean value for the decrease of E dyn0−40 of 22.85% versus a mean of 16.98% in the case of E st0−40 . Other authors have noted likewise an increase in the deformability of other sandstones as the moisture content increase through the decrease of elastic modulus (see Section 1). In this sense, wide ranges were defined by them for this mechanical property (e.g. 32.2–65.7% [30]; 20.63–80.73% [11] from dry to saturated states in both cases). In this study, the range of this variation is reduced for San Crist´ obal’s stone and a decrease between dry and saturated states has been established between 11.1% and 34.3% in the case of E st , and between 12.3% and 39.3% in the case of E dyn . Fig. 10 shows Pareto diagrams with the most frequent ranges to describe the results obtained for the elastic moduli beyond their means and standard deviations. 3.3. Uniaxial compressive strength (UCS) Table 5 and Fig. 11 show the loss of UCS obtained between dry and saturated states for each one of the studied specimens. A mean value for this loss of 29.82% show a notable decrease in the compressive mechanical capabilities of San Crist´ obal’s stone affected by moisture. This mean value is like others obtained for different sandstones. It could be seen in Section 1, where mean values for UCS loss of 20% [20], 40% [20] or 22.7% [21] were referred. These results correspond to new sandstones extracted from their corresponding Fig. 7. Relationship between absorption and porosity. Table 3 Mechanical parameters: Static elastic modulus under different moisture conditions (0%, 40% and 100%). Sp E st (MPa) E st40 (MPa) E st100 (MPa) % 0−40 % 40−100 % 0−100 % 0−40 ∕% 0−100 N01 5970 4557 3970 23.67 12.88 33.50 0.71 N02 10,081 8094 7262 19.71 10.28 27.96 0.70 N03 4715 3812 3723 19.15 2.33 21.04 0.91 N04 4889 4152 3899 15.07 6.09 20.25 0.74 N05 9218 7956 7038 13.69 11.54 23.65 0.58 N06 4204 3636 3205 13.51 11.85 23.76 0.57 N07 5511 4168 3982 24.37 4.46 27.74 0.88 N08 3409 3065 2903 10.09 5.29 14.84 0.68 N09 6752 4939 4768 26.85 3.46 29.38 0.91 N10 3058 2605 2403 14.81 7.75 21.42 0.69 N11 7718 6735 6498 12.74 3.52 15.81 0.81 N12 5754 5290 5115 8.06 3.31 11.11 0.73 N13 5206 4835 3768 7.13 22.07 27.62 0.26 N14 6430 4972 4818 22.67 3.10 25.07 0.90 N15 4479 3933 3913 12.19 0.51 12.64 0.96 N17 4628 3335 3041 27.94 8.82 34.29 0.81 Mean 5751 4755 4394 16.98 7.33 23.13 0.74 SD 1937 1607 1451 6.62 5.45 6.99 0.18 J.R. Baeza et al. Case Studies in Construction Materials 18 (2023) e02128 8 quarries. It has compared results obtained from the studied ancient specimens to those obtained by Verstringe for Dienstian sandstone, from ancient specimens [3] (Section 1). Verstringe studied 3 specimens of Dienstian ferruginous sandstone and obtained a loss of UCS between 50% and 59%. The range obtained for San Crist´ obal’s stone from a larger population is between 2.03% and 64.14%, so greater Fig. 8. Static elastic modulus values under different moisture states. Table 4 Mechanical parameters: Dynamic elastic modulus under different moisture conditions (0%, 40% and 100%). Sp E dyn (MPa) E dyn40 (MPa) E dyn100 (MPa) % 0−40 % 40−100 % 0−100 % 0−40 ∕% 0−100 N01 7509 5444 5399 27.50 0.83 28.10 0.98 N02 11,543 9776 9529 15.30 2.53 17.45 0.88 N03 6357 4591 4462 27.78 2.80 29.81 0.93 N04 6401 4344 4038 32.13 7.04 36.91 0.87 N05 11,948 9415 8851 21.19 6.00 25.92 0.82 N06 5212 3989 3436 23.47 13.86 34.08 0.69 N07 7459 6063 5667 18.72 6.53 24.02 0.78 N08 3755 3109 2931 17.20 5.73 21.94 0.78 N09 8370 7244 6549 13.45 9.60 21.76 0.62 N10 3990 2825 2501 29.20 11.47 37.32 0.78 N11 9579 7737 7558 19.23 2.31 21.10 0.91 N12 6155 5299 5168 13.91 2.47 16.04 0.87 N13 6687 4970 4061 25.68 18.29 39.27 0.65 N14 8787 5432 5403 38.18 0.53 38.51 0.99 N15 6007 4061 3928 32.39 3.28 34.61 0.94 N17 5113 4589 4485 10.25 2.27 12.28 0.83 Mean 7179 5555 5247 22.85 5.97 27.45 0.83 SD 2390 2040 2010 7.98 5.06 8.67 0.11 Fig. 9. Dynamic elastic modulus values under different moisture states. J.R. Baeza et al. Case Studies in Construction Materials 18 (2023) e02128 9 loss of UCS are reached in this case with respect to Dienstian sandstone. In addition to it has been obtained loss of UCS for San Crit´ obal’s stone (64.14%) close to the highest losses found for other sandstones (78.1% [19] or 71.6% [20]), the low values obtained for UCS in dry state are also notable. The range obtained, between 3.09 MPa and 8.73 MPa is similar to that obtained by Verstringe for Dienstian sandstone, but quite lower than the UCS in dry state of other sandstones like those studied by Hawkings (74.5–195.2 MPa) [19], Dyke (11–70 MPa) [18] or Kim (74.5–195.2 MPa) [21]. Fig. 12 shows a Pareto diagram with the most frequent ranges of results. Note the abnormal values of UCS loss obtained for specimens S07 and S10. The same moisture content (100%) does not produce a similar effect on the loss of UCS of the studied specimens. This can be seen in Fig. 13, which represents UCS of dry specimens in a crescent order (blue line) versus the loss of UCS in saturated state (orange line). Results also show that porosity is not the only factor to be considered in the total loss of mechanical properties of the studied stone when it is affected by moisture content. In Fig. 14, it can be seen that the narrow range obtained for porosity does not correspond to the dispersion obtained for the total loss (saturated state) of UCS, E st and E dyn (%) in each one of the specimens studied. Fig. 10. Pareto diagrams of static and dynamic elastic modulus values. Table 5 Mechanical parameters: Uniaxial compressive strength under different moisture conditions (0% and 100%). Sp UCS (MPa) UCS 100 (MPa) Loss (MPa) Loss (% 0−100 ) N01 4.304 2.997 1.31 30.35 N02 8.338 2.990 5.35 64.14 N03 5.283 4.611 0.67 12.72 N04 5.898 3.436 2.46 41.74 N05 8.730 5.374 3.36 38.45 N06 4.845 3.878 0.97 19.95 N07 4.913 4.760 0.15 3.11 N08 3.087 2.754 0.33 10.78 N09 8.199 5.035 3.16 38.59 N10 5.533 5.421 0.11 2.03 N11 6.084 4.640 2.04 30.58 N12 6.029 3.256 2.77 45.99 N13 4.536 2.253 2.28 50.33 N14 4.656 3.683 0.97 20.90 N15 4.241 2.587 1.65 38.99 N17 5.884 4.214 1.67 28.39 Mean 5.697 3.868 1.83 29.82 SD 1.601 1.024 1.39 17.43 J.R. Baeza et al.