Rietveld quantitative phase analysis with molybdenum radiation

TECHNICAL ARTICLE Rietveld quantitative phase analysis with Molybdenum radiation Ana Cuestaa, Gema Álvarez-Pinazoa, Marta García-Matéa, Isabel Santacruza, Miguel A.G. Arandaa,b, Ángeles G. De la Torrea, Laura León-Reinac,*. a Departamento de Química Inorgánica, Universidad de Málaga, Campus Teatinos S/N. 29071-Málaga, Spain. b ALBA-CELLS synchrotron, Carretera BP 1413, Km. 3.3, E-08290 Cerdanyola, Barcelona, Spain. c Servicios Centrales de Investigación SCAI, Universidad de Málaga, 29071Málaga, Spain Abstract Building materials are very complex samples of worldwide importance, hence quantitative knowledge of their mineralogical composition is necessary to predict performances. Rietveld quantitative phase analysis (RQPA) allows a direct measurement of the crystalline phase contents of cements. We highlight in this paper the use of laboratory x-ray powder diffraction (LXRPD) employing high energy radiation, Mo, for attaining the RQPA of cements. Firstly, we evaluate the accuracy of RQPA employing a commercial calcium sulfoaluminate clinker with gypsum. In addition to Mo Kα1 and Mo Kα1,2 radiations, Cu and synchrotron patterns are also analyzed for the sake of comparison. Secondly, the assessment of the accuracy of RQPA results obtained using different radiations (synchrotron, Mo and Cu) and geometries (reflection and transmission) is performed by analyzing two well known commercial samples. As expected, for LXRPD data, accuracy in the RQPA results improves as the irradiated volume increases. Finally, three very complex aged hydrated cements have been analyzed using MoKα1-LXRPD and Synchrotron-XRPD. The main overall outcome of this work is the benefit for RQPA of using strictly monochromatic Mo Kα1 radiation. Best laboratory results arise from Mo Kα1 data as the effective tested volume is much increased but peak overlapping is not swelled. Key words: Mo and Cu radiations, Synchrotron radiation, irradiated volume, cement, accuracy. TECHNICAL ARTICLE I. INTRODUCTION In a standard laboratory instrument, the X-rays are produced in a sealed-tube source, in the same way as they were produced in the original tube discovered by W. C. Rontgen in 1895, where electrons accelerated by a potential difference of up to 60 kV bombard a metal anode inside a vacuum tube. Such sources differ only in the intensity of the radiation produced. The most common target elements are Cu for powder diffraction and Mo for single crystal studies. Alternative radiations, both with lower (Cr, Fe and Co) and higher (Ag and W) energies, are employed for very special applications. For routine powder diffraction work, a Cu tube is the most common choice, giving the wavelength 1.5406 Å. Heavier elements are believed to give too short wavelengths for most practical use in the laboratory, as they exacerbate the peak overlapping, though they become important for total scattering, pair distribution function (PDF) studies and in order to avoid fluorescence from samples containing elements excited by Cu radiation (Dinnebier and Billinge, 2008). On the other hand, the advantages of highenergy penetrating laboratory X-ray sources are i) larger irradiated volumes, ii) lower absorption effects, and iii) more accessible Bragg reflections. However, to keep the angular resolution in powder diffraction is a key point since high-energy patterns are squeezed and therefore, if the appropriate optic elements are not present, peak overlap may become an important drawback. For powder diffraction-based quantitative phase analysis procedures, it is generally accepted that the peak intensities need to be measured to an accuracy of about ± 1-2% relative (Dinnebier and Billinge, 2008). The ability to achieve this goal is strongly influenced by the size of the crystallites in the sample and their number contributing to the Debye-Scherrer cone (Smith, 2001). Reproducible diffraction intensities in 0D or 1D detectors require smooth cones which are obtained from samples containing small TECHNICAL ARTICLE crystallite size(s) and high-enough number of crystallites per phase. Elton and Salt (1996) estimated the number of crystallites diffracting in a sample. Fluctuations in peak intensity between replicate samples arise largely from statistical variation in the number of particles contributing to the diffraction process. It was shown that small changes to the instrumental and sample configurations can significantly improve the sample particle statistics. For a given sample, several methods can be used to increase the number of crystallites contributing to the diffraction pattern, including: i) rotate the sample about the normal to the sample surface for a flat plate sample or the sample axis for a capillary sample; ii) oscillate the sample about the incident angle axis, this motion removes the exact Bragg-Brentano theta/2theta relationship between sample and receiving slit and may lead to aberrations in the peak intensities; iii) repack the sample, recollect and reanalyze the diffraction data, averaging the results from each analysis will produce more meaningful parameter values, iv) reduce the average crystallite size(s) by milling (Buhrke et al., 1998), however, caution must be exercised in the choice of mill since many grinding techniques introduce peak broadening and some phases can undergo solid-solid phase transitions or dehydration during grinding (Hill and Madsen, 2002); and v) enhancing particle statistic by the increasing the diffracting volume. X-ray powder diffraction only concerns a ‘small’ volume of the material, called the irradiated volume, which is determined by the product of the irradiated surface and effective depth. Swapping Cu by Mo radiation, it is possible to deeply penetrate the sample enhancing the irradiated volume which has been employed in gem characterization where the sample cannot be altered (León-Reina et al., 2011). This approach also allows its combination with others listed above in order to maximize the number of crystallites diffracting in a sample. TECHNICAL ARTICLE On the other hand, there is no doubt that Rietveld quantitative phase analysis (RQPA) is one of the most important uses of powder diffraction for analyzing materials, in general (Madsen et al., 2001; Scarlett et al., 2002), and in cements in particular (De la Torre and Aranda, 2003). There are several interlaboratory comparisons that gave some key recommendations for carrying out accurate RQPA and included results relating to the influence of sample related effects such as preferred orientation and microabsorption (Madsen et al., 2001; Scarlett et al., 2002; Stutzman, 2005). Cements are an archetype in RQPA due to is complex phase assemblage with always more than four crystalline phases and usually more than seven/eight crystalline phases for hydrating cements. Laboratory and synchrotron X-ray powder diffraction (LXRPD, SXRPD) (De la Torre and Aranda, 2003) have been thoroughly used for clinker and cements characterization. Rietveld quantitative phase analysis of cement related materials is complex for a number of reasons: (a) high number of phases and the resulting strong peak overlapping; (b) some phases, for instance, alite and gypsum, crystallize as flat plates which may show preferred orientation effects (De la Torre and Aranda, 2003; De la Torre et al., 2004); (c) phases can crystallize as several polymorphs (Dunstetter, 2006; De la Torre et al., 2002, 2008); (d) the number of illuminated crystallites may be not high enough to ensure a random orientation for all diffraction planes; (e) the atomic impurities inside each phase are not known. The mineralogical quantification of selected clinkers and cements was carried out by LXRPD and the Rietveld method employing the data from different laboratories (León-Reina et al., 2009) and allowing the determination of the precision ranges and the general uncertainties for the accuracies for anhydrous cements. Recently, two review articles have been devoted to RQPA of Portland cements (Le Saout et al., 2011) and Portland cements, blended Portland cements and their hydration products (Aranda et al., 2012). TECHNICAL ARTICLE RQPA has been employed for a number of applications related to the hydration reactions of OPC materials (Scrivener and Nonat, 2011). The uses have been expanded from the hydration of model systems (Bellman et al., 2010) to blended cements and the role of admixtures and superplasticizers. RQPA has been used to study the hydration reactions of commercial OPC in reflection geometry with laboratory data (Scrivener et al., 2004). The results were satisfactorily compared to those obtained from thermal analysis and electron microscopy. RQPA, in transmission geometry, was employed for studying OPC hydration products (Mitchell et al., 2006). The data obtained from capillary measurements showed little preferential orientation. This study highlighted the benefits of the transmission geometry as more particles were measured which yields more reliable quantitative results. All these previous studies employed Cu-radiation. To the best of our knowledge, there are not reports dealing with RQPA with Molybdenum radiation for cements or complex samples. Complex samples are defined as those containing more than three crystalline phases. In this article, we highlight the use of LXRPD employing Mo radiation for attaining the RQPA of cements (with selected examples: clinkers, cements and hydrating cement pastes). Firstly, we focus our attention on evaluating the accuracy of RQPA obtained from LXRPD data employing a commercial calcium sulfoaluminate ‘CSA’ clinker mixed with a well known quantity of crystalline gypsum. In addition to Mo Kα1 and Mo Kα1,2 radiations, copper and synchrotron patterns are also analyzed for the sake of comparison. Secondly, the assessment of the accuracy of RQPA results obtained using different radiations (synchrotron, Mo and Cu) and geometries (reflection and transmission) is performed by analyzing two commercial samples, previously used in a Round Robin of building materials (León-Reina et al., 2009). Finally, and for evaluating the case for very complex materials, three aged hydrated cements have been TECHNICAL ARTICLE analyzed using Mo Kα1-LXRPD and SXRPD. The main overall outcome of this work is the benefit for RQPA of using strictly monochromatic Mo Kα1 radiation. II. EXPERIMENTAL A. Sample Preparation To ascertain the accuracy of the methodologies a commercial calcium sulfoaluminate, CSA, cement was mixed with a well known amount, 25 wt%, of commercial micronized natural gypsum, both materials marketed in Europe by BELITH S.P.R.L. (Belgium) (García-Maté et al., 2012), hereafter labeled as 25G_CSA. Two commercial building related materials (León-Reina et al., 2009) were used to establish the accuracy of the methodologies: i) an ordinary grey Portland clinker, labeled as GP_Clin and ii) an ordinary Portland cement type I, labeled as GP_Cem. Three laboratory belite calcium sulfoaluminate (BCSA) (Aranda and De la Torre, 2013) cements were hydrated according to Alvarez-Pinazo et al. (2013), and after 28 days hydration was stopped and samples analyzed. Following the same nomenclature as in Alvarez-Pinazo et al. (2013), G10B0 which is a non-active BCSA with 10 wt% of gypsum and G5B2 and G10B2 which are active BCSAs with 5 and 10 wt% of gypsum, respectively, have been used. These samples have been selected as they are very complex mixtures. B. Transmission Cu Kα and Mo K α LXRPD data acquisition. Table I gives experimental set up details for the three diffractometers used for this type of data collection. 1) D8 ADVANCE DaVinci (Bruker AXS) diffractometer (250 mm of diameter) with Mo radiation equipped with a primary Johansson monochromator Ge (220), which gives TECHNICAL ARTICLE a strictly monochromatic radiation (λ=0.7093 Å), Mo Kα1. The energy dispersive linear detector LYNXEYE XE 500μm, specific for high energetic radiation, was used. 2) EMPYREAN diffractometer (PANalytical B.V.) with a θ/θ goniometer (240 mm of diameter) with Mo radiation equipped with focusing mirror component used in the incident beam path which is capable of converting the divergent beam into a convergent radiation focused on the goniometer circle. The focusing mirror is able to eliminate Mo K β , yielding Mo Kα1,2 radiations. Raw patterns were mathematically treated to strip Mo Kα2, see below. Data were collected preserving constant volume assumption (2theta scan mode). The detector used was the silicon-based position-sensitive detector, X´Celerator, it measures up to 100 times faster than with a traditional point detector, without compromising data quality. 3) EMPYREAN diffractometer (PANalytical B.V.) with a θ/θ goniometer (240 mm of diameter) with Cu radiation equipped with focusing mirror, operating as described just above, yielding Cu Kα1,2 radiations. The geometrical configuration of this diffractometer gives a maximum angle of measurement of 40º, which is low for Cu radiation. Consequently, constant volume assumption was not preserved during data collection (gonio scan mode). The photon counting x-ray detector, PIXCEL 3D, was used. This detector can operate in 1D mode offering a very small strip size and extremely high dynamic range and low noise. The powder samples were placed (for the three diffractometers) in the holders between two Kapton foils. Table II gives details about data acquisition. Moreover, the absorption factors of each sample were experimentally measured by comparison of the direct beam with and without sample. The amount of sample loaded in the sample holders were controlled to obtain a total absorption (µt~1) which corresponds to an absorption factor of ~2.7 or 63% of direct attenuation (Cromer and Liberman, 1981). Table III gives TECHNICAL ARTICLE linear absorption coefficients, fractional attenuation factor of the beam due to absorption (experimentally measured) as well as the calculated thickness (t) by using Lambert-Beer law and a supposed packing fraction of 75%. C. Reflection Cu Kα1 LXRPD data acquisition. Patterns were also recorded in Bragg-Brentano reflection geometry (θ/2θ) on an X'Pert MPD PRO (PANalytical B.V.) diffractometer (240 mm of diameter) using strictly monochromatic Cu Kα1 radiation (λ=1.54059 Å) [Ge (111) primary monochromator]. The X-ray tube worked at 45 kV and 40 mA. The optics configuration was a fixed divergence slit (1/2°), a fixed incident antiscatter slit (1°), a fixed diffracted anti-scatter slit (1/2°) and X'Celerator RTMS (Real Time Multiple Strip) detector, working in scanning mode with maximum active length. D. Transmission synchrotron X-ray powder diffraction (SXRPD). SXRPD patters were collected in Debye-Scherrer (transmission) mode using the X-ray powder diffraction station of ALBA, the Spanish Synchrotron Radiation Facility (Barcelona, Spain) (Knapp et al., 2011). The wavelength, 0.62015(2) Å, was selected with a double-crystal Si (111) monochromator and determined from a Si640d NIST standard (a=5.43123 Å). The diffractometer is equipped with a MYTHEN detector system especially suited for time-resolved experiments. This detector system is not optimized for high-resolution experiments, nevertheless its suitability to perform RQPA has been previously checked (Alvarez-Pinazo et al., 2014). The capillaries of 0.7 mm of diameter were rotated during data collection to improve diffracting particle statistics. The data acquisition time was ∼25 min per pattern to attain very good signal-to-noise ratio over the angular range 1-35º (2θ). The temperature inside the experimental hutch was 299(1) K. TECHNICAL ARTICLE E. XRPD data analysis. The focusing mirror used in EMPYREAN diffractometers causes a wavelength shift of Kα2 radiation. The effect is very small for copper wavelength, but it becomes noticeable for short wavelengths like molybdenum radiation. Consequently, Mo Kα2 data were stripped by using the modified wide Rachinger (1948) algorithm of Delhez and Mittemeijer (1975) as implemented in HighScore+ (v. 3.0e) PANalytical software, by using Kα2 shift value of 0.005, Kα2/ Kα1 intensity ratio of 0.6 and a wavelength ratio correction of 0 ppm. In order to obtain RQPA, all patterns were analyzed by using the Rietveld methodology as implemented in the GSAS software package (Larson and Von Dreele, 1994). Crystal structure descriptions used for all the phases were those reported in Aranda et al. (2012). Final global optimized parameters were: background coefficients, zero-shift error, cell parameters, peak shape parameters and March-Dollase (Dollase, 1986) preferred orientation parameter, when appropriated. Peak shapes were fitted by using the pseudo-Voigt function (Thompson et al., 1987) with the asymmetry correction of Finger et al. (1994) included. III. RESULTS AND DISCUSSIONS A. Characterization of peak widths. The instrumental contribution to peak broadening for LXRPD and SXRPD was determined with Standard Reference Material (SRM) LaB6 and Na2Ca3Al2F14 (NAC) standards, respectively. Figure 1 shows measured full width at the half maximum, FWHM, as a function of angle for all the diffractometers and configurations used in this study. TECHNICAL ARTICLE Three hydrated cements have been analyzed using strictly monochromatic Mo Kα1 radiation. RQPA results were crosschecked by comparison to the results from SXRPD data for the same samples. In addition to some remaining phases from the anhydrous cements, three hydrated crystalline phases are expected in these types of pastes: ettringite, stratlingite and katoite (Alvarez-Pinazo et al., 2013, 2014). Some amounts of calcium carbonate (calcite and vaterite) were also quantified. These carbonates likely arise from the carbonation of portlandite, Ca(OH)2, which is one of the hydration products of dicalcium silicate, a.k.a. belite. The complexity of these systems is clear from Table VII as eight crystalline phases are present. Figure 5 gives Rietveld plots for G10B0 sample (Mo Kα1 and synchrotron patterns) as a representative example. Figure 5 highlights the complexity of the sample (with eight crystalline phases) but also the highresolution features the Mo Kα1 pattern, where the diffraction peak overlapping is very similar to that observed in the synchrotron pattern. Two main conclusions can be derived from the RQPA results reported in Table VII. Firstly, the carbonation effect are clearly observed in these patterns with the calcium carbonate (calcite and vaterite phases) slightly evolving with time. Secondly, and in spite of the carbonation effects and the complexity of the systems, the derived contents for the main crystalline phases agree relatively well in both studies. IV. CONCLUSION Irradiated volume in diffraction is a key issue since higher volume yields enhanced particle statistics. Therefore, the use of a high energy radiation is beneficial as the irradiated volume of sample can be increased. Moreover, quite low FWHM values for strictly monochromatic Mo Kα1 diffraction peaks have been measured. Low FWHM TECHNICAL ARTICLE values indicate that peak overlapping is not much more important than in Cu Kα1 powder diffraction. So, the optimum results for strictly monochromatic Mo radiation arise from the large tested volumes meanwhile peak overlapping is not enlarged. ACKNOWLEDGMENTS This work has been supported by Junta de Andalucía through P11-FQM-7517 research grant and by Spanish MINECO through MAT2010-16213 research grant, which is cofunded by FEDER. I. Santacruz thanks a Ramón y Cajal fellowship, RYC-2008-03523. PANalytical B.V. (Almelo, The Netherland) and Bruker (Karlsruhe, Germany) are thanked by providing the Mo-radiation diffractometers. ALBA is thanked for providing synchrotron beamtime at BL04-MSPD beamline. References Alvarez-Pinazo, G., Santacruz, I., León-Reina, L., Aranda, M. A. G., and De la Torre, A. G. 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"Outcomes of the International Union of Crystallography Commission on Powder Diffraction Round Robin on Quantitative Phase Analysis: samples 2, 3, 4, synthetic bauxite, natural granodiorite and pharmaceuticals,” J. Appl. Cryst. 35, 383-400. Scrivener, K. L., Fullmann, T., Gallucci, E., Walenta, G. and Bermejo, E. (2004). “Quantitative study of Portland cement hydration by X-ray diffraction/Rietveld analysis and independent methods,” Cem. Concr. Res. 34 1541-1547. Scrivener, K. L., and Nonat, A. (2011). “Hydration of cementitious materials, present and future,” Cem. Concr. Res. 41 651-665. Smith, D. K. (2001). “Particle statistics and whole-pattern methods in quantitative X-ray powder diffraction analysis,” Powder Diffr., 16, 186-191. Stutzman, P. (2005). “Powder diffraction analysis of hydraulic cements: ASTM Rietveld round-robin results on precision,” Powder Diffr., 20, 97-100. Thompson, P., Cox, D. E. and Hasting, J. B. (1987). “Rietveld refinement of DebyeScherrer synchrotron X-ray data from Al2O3,” J. Appl. Cryst. 20, 79-83. TECHNICAL ARTICLE Tables Table I. Transmission laboratory X-ray powder diffraction experimental setups with flat samples. Mo Kα1-D8 Mo Kα1,2-EMPYREAN Cu Kα1,2-EMPYREAN X-ray tube λ (Å) Ceramic Mo - long fine focus 0.70932 Ceramic Mo - long fine focus 0.7107 Ceramic Cu - long fine focus 1.5418 Applied power 50 kV, 45 mA 60 kV, 40 mA 45 kV, 40 mA Tube focus Long line Line Line Flat sample stage transmission spinner (10 rpm) transmission spinner (60 rpm) transmission spinner (15 rpm) Incident beam optics Optic device Johansson monochromator Ge (220) Focusing X-ray mirror for Mo radiation Focusing X-ray mirror for Cu radiation Beam width (Bw) 16 mm 20 mm 12.9 mm Soller slit 1.6º (0.028 rad) 0.02 rad 0.04 rad Divergence slit (Sw) 2 mm 0.7 mm 0.7 mm Anti-Scatter slit -- ¼º ½º Diffracted beam optics Anti-Scatter slit -- 2 mm 5 mm Soller slit 1.6º (0.028 rad) 0.02 rad 0.04 rad Detector LYNXEYE XE 500μm (3.5˚ opening) X’CELERATOR (scanning mode 2.122 o active length) PIXCEL 3D RTMS (scanning mode 3.347 o active length) TECHNICAL ARTICLE Table II. Data acquisition details for LXRPD patterns collected using Mo and Cu radiations in transmission (t) and reflection geometries (r). Angular range (º) step size (º) Average total time (min) D8 (Mo Kα1) (t) 3-30 0.009 150 EMPYREAN (Mo Kα2-strip) (t) 3-31 0.017 100 EMPYREAN (Cu Kα1,2) (t) 5-70 0.013 170 X’PERT (Cu Kα1) (r) 5-70 0.013 120 Table III. Density (ρ), linear absorption coefficient (µ), fractional attenuation factor of the beam due to absorption (a.f.) and thickness (t) of flat samples for transmission LXRPD measurements. Sample ρ (g/cm 3 ) Mo Kα 1 Mo Kα 2-strip Cu Kα 1,2 µ (cm-1) 24 24 205 25G_CSA 2.7 a.f. 2.5 2.7 3.0 t (mm)* 0.5 0.5 0.07 µ (cm-1) 36 36 320 GP_Clin 3.3 a.f. 2.2 2.1 2.9 t (mm)* 0.3 0.3 0.04 µ (cm-1) 35 35 307 GP_Cem 3.2 a.f. 2.2 2.5 2.7 t (mm)* 0.3 0.3 0.04 *75% packing factor is assumed TECHNICAL ARTICLE Table IV. Comparative of the RQPAs for sample 25G_CSA measured with different radiations (Mo, Cu and Synchrotron) and geometries (reflection (r) and transmission (t)). Phase (wt%) Comments DTA-TG wt% Synchr λ=0.62 Å t-capillary Mo Kα 1 t-flat Mo Kα 2-strip t-flat Cu Kα 1 r-flat Cu Kα 1,2 t-flat µ [Cu Kα] (cm -1 ) µ [Mo Kα] (cm -1 ) µ [λ=0.62 Å] (cm -1 ) C4A3S 51.7(1) 47.5(2) 51.5(2) 47.9(1) 50.6(1)/51.1(1)* 171 19 13 β-C2S 12.7(3) 17.1(5) 11.5(7) 11.0(3) 11.0(5)/10.5(5)* 299 34 23 C4AF 1.2(1) - - 0.7(1) - 388 58 39 CT 6.4(1) 6.4(2) 7.1(3) 6.8(2) 7.6(2)/7.5(2)* 485 57 38 MgO 1.9(1) 1.5(1) 1.8(2) 1.4(1) 1.0(1)/0.9(1)* 100 10 7 Ca2MgSi2O7 - - 1.3(2) 1.4(1) 1.1(2)/1.1(2)* 204 23 15 CaSO4 . 2H2O (CSH2) 24.96 26.1(2) 27.6(3) 26.8(3) 31.0(1) 28.7(2)/28.9(2) * 140 16 11 P.O.C. CSH2 [0 1 0] 1.00 1.180(7) 1.085(8) 0.732(2) 1.300(7)/1.290(7)* * Rietveld quantitative phase analysis obtained after the application of the correction factor due to not preserving constant volume assumption. TECHNICAL ARTICLE Table V. Comparative of the RQPAs for sample GP_Clin measured with synchrotron, Mo and Cu radiations, as in Table IV. Phase (wt%) $R.R. Synchr λ=0.62 Å t-capillary Mo Kα 1 t-flat Mo Kα 2-strip t-flat Cu Kα 1,2 t-flat µ [Cu Kα] (cm -1 ) µ [Mo Kα] (cm -1 ) µ [λ=0.62 Å] (cm -1 ) C 3 S 66.6(2. 8) 63.1(1) 62.7(3) 62.1(1) 56.5(2)/ 56.2(2)* 313 36 24 C 2 S 19.2(2. 5) 20.0(3) 21.9(4) 21.7(4) 26.3(5)/ 26.7(5)* 299 34 23 C3A 2.4(0.5) 3.1(2) 2.3(2) 2.7(2) 2.4(2)( 2.3(2)* 260 30 20 C4AF 9.9(1.2) 12.1(3) 11.7(2) 11.9(2) 13.6(2)/13.7(3)* 388 33 22 NaK3(SO4)2 0.8(0.2) 0.6(1) 0.7(1) 0.7(1) 0.6(1)/0.5(1)* 195 22 15 MgO 1.0(0.2) 1.0(1) 0.9(1) 0.9(1) 0.6(1)/0.5(1)* 100 10 7 P.O.C. C3S [1 0 -1] 1.0(-) 1.020(3) 1.034(4) 1.040(4)/1.040(4) * $ Mean and standard deviation values from the Round Robin study (León-Reina et al., 2009). In this case, the average values and the standard deviations were derived from the results of the fourteen participants. * Rietveld quantitative phase analysis obtained after the application of the correction factor due to not preserving constant volume assumption. Figure 4 Gypsum Bassanite C3S C4AF C3S C3S C3S C3S C3S C3AC4AF C3S C3S C2S 2-Theta, deg I (a.u.) I (a.u.) I (a.u.) (a) 2-Theta, deg 2-Theta, deg (b) (c) 2-Theta, deg Figure 5 4.0 6.0 8.0 10.0 12.0 14.0 16.0 Ett Ett Ett Ett Ett Ett, β-C2S Ett Stratl Stratl Stratl Katoite Katoite Katoite Katoite Ett β-C2S β-C2S C2AS Ett Calcite Vaterite Vaterite γ-C2S (a) I (a.u.) 2-Theta, deg MoKα1 4.0 6.0 8.0 10.0 12.0 14.0 Ett Ett Ett Ett Ett Ett, β-C 2 S Ett Stratl Stratl Stratl Katoite Katoite Katoite Katoite Ett β-C 2 S β-C 2 S C 2 AS Ett Calcite Vaterite Vaterite γ-C 2 S γ-C 2 S I (a.u.) 2-Theta, deg (b) λ= 0.62 Å