Elsevier Editorial System(tm) for Cement and Concrete Research Manuscript Draft Manuscript Number: CEMCON-D-11-00691R1 Title: Rietveld quantitative phase analysis of Yeelimite-containing cements Article Type: Research Paper Keywords: 4CaO.3Al2O3.CaSO4 Sulfoaluminate X-Ray Diffraction Amorphous Material Characterization Corresponding Author: Dr MIGUEL A. G. ARANDA, PhD Corresponding Author's Institution: Universidad de Málaga First Author: Gema Álvarez-Pinazo Order of Authors: Gema Álvarez-Pinazo; Ana Cuesta; Marta García-Maté; Isabel Santacruz; Enrique R Losilla; Angeles G De la Torre; Laura León-Reina; MIGUEL A. G. ARANDA, PhD Abstract: Yeelimite-containing cements are attracting attention for their tailored properties. Calcium sulfoaluminate, CSA, cements have high contents of Yeelimite and they are used for special applications. Belite calcium sulfoaluminate, BCSA or sulfobelite, cements have high contents of belite and intermediate contents of Yeelimite, and they may become an alternative to OPC. Here, we report Rietveld quantitative phase analyses for three commercially available CSA clinkers, one CSA cement, and two laboratory-prepared iron-rich BCSA clinkers. The crystalline phases are reported and quantified. Selective dissolutions are employed for BCSA clinkers to firmly establish their phases. Finally, the overall unaccounted contents (amorphous plus crystalline not quantified) have been determined by two approaches: i) external standard procedure (G-method) with reflection data; ii) internal standard procedure (spiking method with ZnO) with transmission data. The overall unaccounted contents for CSA clinkers were ~10 wt%. Conversely, the unaccounted contents for BCSA clinkers were higher, ~25 wt%. *Manuscript Click here to download Manuscript: CEMCON-D-11-00691_RQPA_Yeelemite_cements_rCelviciske hde.droe cto view linked References 1 Revised manuscript (CEMCON-D-11-00691) submitted to Cement and Concrete Research 2 Rietveld quantitative phase analysis of Yeelimite-containing cements 1 1 1 1 1 1 3 G. Álvarez-Pinazo , A. Cuesta , M. García-Maté , I. Santacruz , E. R. Losilla, A. G. De la Torre , 2 ,1 4 L. León-Reina and M. A. G. Aranda* 1 5 Departamento de Química Inorgánica, Cristalografía y Mineralogía, Universidad de Málaga, 6 29071 Málaga, Spain 2 7 Servicios Centrales de Apoyo a la Investigación, Universidad de Málaga, 29071-Málaga, Spain 8 Abstract. 9 Yeelimite-containing cements are attracting attention for their tailored properties. Calcium 10 sulfoaluminate, CSA, cements have high contents of Yeelimite and they are used for special 11 applications. Belite calcium sulfoaluminate, BCSA or sulfobelite, cements have high contents of 12 belite and intermediate contents of Yeelimite, and they may become an alternative to OPC. Here, 13 we report Rietveld quantitative phase analyses for three commercially available CSA clinkers, one 14 CSA cement, and two laboratory-prepared iron-rich BCSA clinkers. The crystalline phases are 15 reported and quantified. Selective dissolutions are employed for BCSA clinkers to firmly establish 16 their phases. Finally, the overall unaccounted contents (amorphous plus crystalline not quantified) 17 have been determined by two approaches: i) external standard procedure (G-method) with reflection 18 data; ii) internal standard procedure (spiking method with ZnO) with transmission data. The overall 19 unaccounted contents for CSA clinkers were ~10 wt%. Conversely, the unaccounted contents for 20 BCSA clinkers were higher, ~25 wt%. . . 21 Keywords: 4CaO 3Al2O3 CaSO4; calcium sulfoaluminate; X-Ray Diffraction analysis; Rietveld 22 method; amorphous material * 23 Corresponding author. Tel.: +34952131874; fax: +34952132000; E-mail address: 24 g_aranda@uma.es (Miguel A. G. Aranda) 1 25 1. Introduction. 26 Calcium sulfoaluminate (CSA) cements have been applied worldwide from the 60‘s as expansive 27 binders mixed with Portland cements [1]. These cements are characterised by containing high 28 amounts of Yeelimite, also called Klein‘s salt or tetracalcium trialuminate sulfate (C4A3S). 29 Hereafter, cement nomenclature will be used, i.e. C=CaO, S=SiO2, A=Al2O3, F=Fe2O3, M=MgO, 30 S=SO3, C=CO2, H=H2O, K=K2O and N=Na2O. Therefore, C4A3S corresponds to Ca4Al6O12(SO4). 31 During the 70‘s, CSA cements were introduced into the Chinese market as high performance and 32 dimensionally stable cementitious matrices developed by China Building Materials Academy [2]. In 33 Europe, the use of CSA cements is strongly limited by the lack of standards concerning special 34 cements derived from non-Portland clinkers. Nevertheless, their manufacture has recently been 35 started by several companies. The main uses of these CSA cements, or blends with Portland 36 cements, are for quick repairs and pre-cast products or floor concrete applications. 37 Moreover, Yeelimite-containing cements have become highly popular over the last few years for 38 research. The driving force for these investigations is much lower CO2 emissions in their 39 manufacture when compared to those of Portland cement production due to the following main 40 reasons [3,4]: i) Yeelimite releases during its synthesis only a third part of the CO2 released by the 41 production of alite, ii) firing temperature is about 200ºC lower than that of OPC clinker, iii) various 42 industrial by-products can be used in the kiln feed, and iv) Yeelimite-containing clinkers are easier 43 to grind than OPC clinkers. The improvement of cement performances and the reduction of the 44 environmental impact related to its manufacture are most likely the main areas of innovation for the 45 cement industry [5]. It must be highlighted that CSA cements may have important special 46 applications such radioactive element encapsulation in high-density cement pastes [6]. Other 47 interesting properties of Yeelimite-containing cements are high early strengths, short setting times, 2 48 low solution alkalinity as well as high impermeability and chemical resistance against several 49 aggressive media [7]. 50 However, while the composition of Portland cement is defined by long-standing codes and 51 standards, there is no corresponding compositional framework for Yeelimite-containing cements. 52 These clinkers may show very variable phase assemblage. The raw mix composition can be based 53 on conventional raw materials (limestone, clay, bauxite and iron ores); in addition, industrial by- 54 products and wastes can also be added [8,9]. Yeelimite-containing cements could be classified 55 according to their C4A3S contents as: 56 I) Calcium Sulfo-Aluminate (CSA) cements which would refer to those with high C4A3S 57 contents. They may be prepared from CSA clinkers containing C4A3S as the main phase ranging 58 between 50 to 90 wt% [10]. The calcium sulfate addition is very important as it may profoundly 59 affect the properties of the resulting binder [11-13]. The calcium sulfate source and content have 60 to be customized for a given application. These cements can be used alone or in combination 61 with other cements to provide an improved early resistance, low shrinkage, high 62 impermeability, and a strong resistance to sulfate attack. 63 II) Belite Calcium Sulfo-Aluminate (BCSA) cements which would refer to those with C2S 64 (belite) as the main phase and intermediate C4A3S contents. These cements, also known as 65 sulfobelite, are prepared from clinkers containing more than 40-50 wt% of C2S and 20-30% 66 C4A3S. The most common formulation of BCSA clinkers consists on -C2S, C4A3S and C4AF 67 [6, 14-18]. These are iron-rich BCSA cements, also termed as BCSAF, and they are produced at 68 ~1250ºC and show a rapid hardening, excellent durability, self-stressing and volume stability, 69 depending on the amount of gypsum added [19]. Recently, a new class of BCSAF cement has 70 been proposed by Lafarge [15,20,21] in which stabilization of high temperature belite 3 71 polymorphs (-forms) has been promoted (for instance with borax) to enhance early age 72 hydration of these cements. 73 Alternatively, in order to further enhance mechanical strengths at very early ages, <1 day, C4AF 74 phase may be substituted by C12A7; however, the clinkering temperature should be increased 75 ~100ºC and the durability with respect to sulfate attack is limited [22,23]. This formulation 76 corresponds to aluminium-rich BCSA clinkers (or BCSAA) with C2S, C4A3S, C12A7 and CA as 77 main phases [24]. In this type of clinkers, aluminate phases and C4A3S are responsible for the 78 early strength development, while C2S provides hardening at much later ages. An in-situ study 79 of the clinkering of both BCSAF and BCSAA samples has been very recently reported using 80 high-energy synchrotron X-ray powder diffraction [25]. 81 III) Alite Calcium Sulfo-Aluminate (ACSA) cements which would correspond to those 82 characterized by the simultaneous presence of C3S and C4A3S phases. In this special case, 83 Yeelimite phase content may be even higher than that of alite [26]. Other phases may appear in 84 the clinkers including C2S and C3A. However, this type of clinker is quite difficult to prepare 85 because the optimum temperatures for the synthesis of the two phases differ considerably. 86 Nevertheless the addition of a small amount of CaF2 (and/or CuO, TiO2) to the raw mixes 87 allows the coexistence of both phases at temperatures between 1230 and 1300°C. 88 CSA and BCSA clinkers are complex materials due to the presence of many crystalline phases, 89 some of them also displaying polymorphism. X-ray powder diffraction (XRPD) is the most 90 appropriate technique to identify, characterize and quantify the crystalline phases within these 91 samples. The application of Rietveld methodology [27] to XRPD data in order to obtain quantitative 92 phase analyses (RQPA) was reported long time ago [28]. To derive the phase contents from the 93 Rietveld optimised scale factors, this methodology normalizes the results to 100% of crystalline 94 phases (i.e. the presence of amorphous content is not taken into account). Therefore, if the mixture 4 95 has an appreciable amount of amorphous phase, this method is considered as semi-quantitative. To 96 overcome this problem, two approaches have been developed, the internal and the external standard 97 methods (to be briefly described just below). The presence of a glassy or amorphous component in 98 Portland cements and clinkers has been debated by several authors [29-31]. 99 I) Internal standard method or ―spiking method‖, which consists on the addition of a known 100 amount of a crystalline standard, Wst. This standard must be free of amorphous content or at 101 least it should contain a known non-diffracting content. This (artificial) mixture must be well 102 homogenised since the particles should be randomly arranged. The addition of the standard will 103 dilute the crystalline phases within the samples, hence this may be a problem for low-content 104 phases. A procedure for Rietveld quantitative amorphous content analysis was outlined 105 elsewhere [32] and the effects of systematic errors in the powder patterns were studied. A very 106 recent report uses this methodology in depth [33]. This method permits the determination of an 107 overall unaccounted content which is composed by amorphous phase(s), misfitting problems of 108 the analysed crystalline phases, and because some crystalline phases may not be included in the 109 control file due to several reasons (its crystal structure is not known, the phase was not 110 identified, etc.). This overall content is hereinafter named ACn which stands for Amorphous and 111 Crystalline not-quantified, to highlight that not only an amorphous fraction but any not- 112 computed crystalline phase and any misfit problem (for instance the lack of an adequate 113 structural description for a given phase) may contribute to this number. 114 II) External standard method (G-factor approach), which consists in recording two patterns (one 115 for the sample and another for the standard). It is possible to use an external standard method to 116 avoid the complications that may arise from mixing an internal standard with the sample. This 117 approach requires the recording of two patterns in identical diffractometer 118 configuration/conditions for Bragg-Brentano  reflection geometry. The method was 5 119 proposed by O‘Connor and Raven [34] and very recently applied to anhydrous cements [35] and 120 to pastes [36]. This methodology is also known as G-method since the standard allows 121 calculating the G-factor of the diffractometer in the operating conditions. This calculated G- 122 factor represents a calibration factor for the whole experimental setup and comprises the used 123 diffractometer, radiation, optics, and all data acquisition conditions (f.i. detector configuration, 124 integration time, etc.). It is experimentally more demanding but it may have the brightest future 125 as it does not interfere with the hydration reactions. 126 In this work, we report Rietveld quantitative phase analysis for several Yeelimite-containing 127 clinkers and cements. Both CSA and BCSAF clinkers have been studied to illustrate the suitability 128 of Rietveld methodology. Furthermore, the ACn contents have been determined using both 129 strategies, internal and external standard procedures. The obtained results are discussed. 130 2. Experimental section. 131 2.1. Material description. 132 In this work, six different types of Yeelimite-containing samples have been investigated. Three of 133 them are commercially available CSA clinkers. A CSA cement prepared in an industrial trial, but 134 not commercially available, has been also studied. Finally, two BCSAF clinkers prepared in our 135 laboratory have been also analysed. 136 2.1.1. Commercial CSA clinkers. 137 The following commercial clinkers with high C4A3S contents (ranging between 55 to 70 wt%) have 138 been studied: 139 - ALIPRE® (2009), a CSA clinker industrially produced by Italcementi Group. 140 - BELITH_CS10, a CSA clinker industrially produced in China and marketed in Europe by Belith 141 (Belgium). 6 142 - S.A.cement, a CSA clinker industrially produced by Buzzi Unicem. 143 2.1.2. Non-commercial CSA cement. 144 It has also been studied a CSA cement, with ~ 40% C4A3S, produced in an industrial trial which is 145 not commercially available. This cement is named CSA_trial in this study. 146 2.1.3. Laboratory-prepared BCSAF clinkers. 147 Approximately two kilograms of two BCSAF clinkers have been prepared in our laboratory in 148 several steps. The raw materials were weighed to have an expected phase composition of 50 wt% 149 C2S, 30 wt% of C4A3S and 20 wt% of C4AF. Table 1 shows the amounts of raw materials used for 150 the preparations. The difference in both samples is the addition of borax in one of them, 2 wt% 151 expressed as B2O3 in the resulting clinker. Hereafter, these clinkers are named BCSAF_B0 and 152 BCSAF_B2, for boron-free and boron-containing clinker, respectively. The raw materials mixture 153 (approximately 3 kilograms) was pre-homogenised for 15 minutes in a micro-Deval machine 154 (A0655, Proeti S.A., Spain) at 100 rpm with steel balls (9 balls of 30 mm, 21 balls of 18 mm and a 155 number of balls of 10 mm up to a total ball weight of 2500 g). The mixture was pressed into pellets 156 of about 40 g (55 mm of diameter and approximately 5 mm of height). Six pellets, one on top of 157 each other, were placed in a large Pt/Rh crucible of 325 ml of volume. The pellets were heated at 158 900ºC and held for 30 min (heating rate of 5 ºC/min). Then, they were further heated at 1350ºC and 159 held for another 30 min (heating rate of 5 ºC/min). Finally, the samples were quenched with air 160 flow. The clinkered pellets were grinded in the micro-Deval mill at 100 rpm for 1 hour. Under these 161 milling conditions, all clinker material passed through a 250 m sieve. 162 2.1.4. Selective dissolution of laboratory-prepared BCSAF clinkers. 163 Selective dissolutions have been performed to study the laboratory-prepared BCSAF clinkers [37]. 164 Initially, these clinkers were ground to a Blaine fineness of ~ 400 m²/kg. 7 165 Selective dissolution to remove the aluminate phases (silicate residue). A solution composed of 166 60 ml demineralised water, 8 g of KOH and 8 g of sucrose was heated to 95 °C with magnetic 167 stirring in a 250 ml beaker. After around 30 minutes, it becomes brown-yellow. Then, 4 g of clinker 168 powder was added and kept under stirring for 15 minutes. After this treatment, the resulting 169 suspension was filtered with a Whatman system (Whatman filter with diameter 70 mm). Once this 170 initial filtration step was finished, the minimum amount of water was added to eliminate the sucrose 171 and finally the residue was rinsed twice with isopropyl alcohol to remove water. After filtration, the 172 residue was mashed with a spatula to break up agglomerated particles, dried and analyzed by 173 XRPD. 174 Selective dissolution to remove the silicate phases (aluminate residue). A mixture of 4 g of 175 clinker powder, 52 ml methanol and 24 g salicylic acid was prepared. This mixture was stirred in a 176 250 ml beaker with a glass cover for 50 minutes. After that treatment, the mixture was filtered with 177 a Whatman system (Whatman filter with diameter 70 mm) and rinsed with ethanol. The residue was 178 dried in an oven at 60ºC for 30 minutes, ground and analyzed by XRPD. 179 2.2. Analytical techniques. 180 2.2.1. Elemental analysis by X-ray fluorescence. 181 Table 2 gives the elemental analysis for the 6 studied samples prepared as fused beads. The X-ray 182 fluorescence (XRF) data were taken in a Magic X spectrometer (PANalytical, Almelo, The 183 Netherlands) using the calibration curve of silica-alumina materials. The elemental analyses of the 184 raw materials used for the BCSAF clinker preparations are available upon request, but they are not 185 reported here since the analyses of the clinkers are provided. 186 2.2.2. Inductively coupled plasma mass spectroscopy (ICP-MS). 8 187 The amounts of Na2O and B2O3 in the laboratory-prepared BCSAF clinkers were determined by 188 ICP-MS on Perkin Elmer spectrophotometer (Nexion 300D). Previously, the samples were digested 189 in an Anton Paar device (Multiwave 3000) by using HNO3, HCl and HF. 190 2.2.3. Laboratory X-ray powder diffraction. 191 All six samples were studied by laboratory X-ray powder diffraction (LXRPD) to identify, 192 characterize and quantify the crystalline phases. In order to study the ACn contents, both internal 193 and external standard approaches were employed. 194 On the one hand, the patterns studied by the external standard method were recorded in Bragg- 195 Brentano reflection geometry (/2) on an X'Pert MPD PRO diffractometer (PANalytical B.V.) 196 using strictly monochromatic CuKα1 radiation (λ=1.54059Å) [Ge (111) primary monochromator]. 197 In addition to the patterns for the samples to be studied, this approach requires the recording of 198 additional patterns collected in identical diffractometer configuration/conditions for the standard, in 199 this case -Al2O3 (SRM-676a). The X-ray tube worked at 45 kV and 40 mA. The optics 200 configuration was a fixed divergence slit (1/2°), a fixed incident antiscatter slit (1°), a fixed 201 diffracted anti-scatter slit (1/2°) and X'Celerator RTMS (Real Time Multiple Strip) detector, 202 working in scanning mode with maximum active length. Data were collected from 5º to 70° (2θ) for 203 2 hours. The samples were rotated during data collection at 16 rpm in order to enhance particle 204 statistics. NIST standard reference material SRM-676a, corundum (-Al2O3) powder, has been 205 certified to have a crystalline phase purity of 99.02%  1.11% (95% confidence interval) by RQPA 206 against a suitable primary standard, powder silicon carefully prepared from a single crystal [33]. 207 On the other hand, the patterns studied by the internal standard method were recorded in flat- 208 sample transmission geometry on an EMPYREAN diffractometer (PANalytical B.V.) equipped 209 with a / goniometer, CuK1,2 radiation (λ=1.542Å) and a focusing mirror. This PreFIX optical 9 210 component is capable of converting the divergent beam into a convergent radiation focused on the 211 goniometer circle. The EMPYREAN diffractometer was equipped with fixed incident and diffracted 212 beam anti-scatter slits of ¼ º and 5 mm, respectively. The detector was PIXCEL 3D RTMS, which 213 comprises more than 65000 pixels, each 5555 microns in size; each having its own circuitry. As 214 internal standard, ZnO (99.99%, Sigma-Aldrich, St. Louis, MO, USA), was added to the samples to 215 a total content of 25 wt%. The mixtures were homogenized for 20 minutes in an agate mortar. The 216 powder samples (mixed with ZnO) were placed in the holders between two Kapton films. The 217 cylindrical sample diameter and thickness were ~10.0 mm and ~0.3 mm, respectively. The overall 218 measurement time was ~3 h per pattern to have very good statistic over the 2θ range of 5-70º with 219 0.0131º step size (2). 220 2.2.4 XRPD data analysis. 221 Powder patterns of the samples were analyzed by the Rietveld method as implemented in the GSAS 222 software package [38] by using a pseudo-Voigt peak shape function [39] with the asymmetry 223 correction included [40] to obtain Rietveld Quantitative Phase Analysis (RQPA). The refined 224 overall parameters were: phase scale factors, background coefficients, unit cell parameters, zero- 225 shift error, peak shape parameters and preferred orientation coefficient, if needed. March-Dollase 226 ellipsoidal preferred orientation correction algorithm was employed [41]. In addition to these 227 parameters, and only for the Rietveld refinements of transmission powder data, a flat-sample 228 absorption coefficient was also optimized as implemented in GSAS. Table 3 reports the crystal 229 structures used in this study to simulate the crystalline phase powder patterns [references 42-59]. 230 The powder diffraction file (PDF) codes for all identified phases in the studied cements are also 231 given in Table 3. 10 232 The output of a RQPA study for a sample with m-crystalline phases is a set of m-crystalline phase 233 scale factors, mS. A phase scale factor, S, is related to the phase weight content, W, by 234 equation 1 [28]. W 235 S = K  e (1) (ZMV) s 236 Where Ke is a constant which depends on the diffractometer operation conditions, s is the sample 237 mass absorption coefficient, Z is the number of chemical units/formulas within the unit cell of - 238 phase, M is the molecular mass of the chemical formula for -phase, and V the unit cell volume for 239 -phase. Once the crystal structure is known, the ‗ZMV‘ term is known. The parameter of interest, 240 W, depends on the phase scale factor, S, but also on Ke and s. Unfortunately, these two variables 241 are not known and they can not derived from the single powder diffraction pattern of the sample 242 under study. 243 Currently, there are three main ways to derive the phase content, W, from the Rietveld refined 244 scale factor, S. These three methods are based on different mathematical approaches and they have 245 different experimental complexities. They are very briefly discussed below. 246 2.2.4.1 Normalization to full crystalline content method. 247 The simplest approach is the approximation that the sample is only composed of crystalline phases 248 with known structures. These crystal structures are used to compute the powder pattern with any 249 Rietveld program code, in this case GSAS. Under this approximation, W is given by equation (2) 250 [28]: S (ZMV) 251 W =   (2) m Si (ZMV)i i1 11 252 The use of equation (2) in RQPA eliminates the need to measure the instrument calibration 253 constant, Ke, and the sample mass absorption coefficient, s. However, the method normalizes the 254 sum of the analysed weight fractions to 1.0. Thus, if the sample contains amorphous phases, and/or 255 some amounts of unaccounted crystalline phases, the analysed weight fractions will be 256 overestimated. This approach is by far the most widely used method in RQPA. However, it must be 257 highlighted that the resulting weight fractions are only accurate if the ACn amount is very small 258 (negligible). 259 2.2.4.2 External standard method (G-factor approach). 260 One possibility to quantify the amount of the ACn content is to use the G-factor approach by 261 employing a suitable external standard. In this approach, the diffractometer constant, Ke, is 262 calculated according to equation 3 (in this case the standard was NIST Al2O3) [34]:  V2  263 G = Ke = Sst st st st (3) Wst 264 where Sst is the Rietveld scale factor of the (external) standard, st is density of the standard, Vst is 265 the unit cell volume of the standard, Wst is weight fraction the standard (in our case 100 wt%), all 266 values derived from the Rietveld refinement of the external standard pattern collected in identical 267 conditions than those of the cements. μst is the mass attenuation coefficient of the standard. This G- 268 factor (the average of three independent measurements) was used to determine the mass 269 concentration of each phase in the RQPA of the Yeelimite-containing cements by equation 4:  V2  270 W = S    s  (4) G 271 This method allowed determining the absolute weight fractions by previously obtaining the 272 diffractometer constant. However, the mass attenuation coefficient of the samples are needed, s. 12 273 These values were independently determined by X-ray fluorescence analysis from data in Table 2. 274 The calculated G factor for NIST Al2O3, as well as selected structural details of the used standard, is 275 given in Table 4. The mass attenuation coefficients (MAC) of the individual oxides (calculated with 276 the HighScore Plus 2.2 program) were given in Table 2. Furthermore, the MAC values of the six 277 studied samples were also given in that Table. 278 2.2.4.3 Internal standard method. 279 An alternative method to quantify the ACn content is to use the internal standard method. In this 280 approach, the sample is spiked with an appropriate standard that should fulfil at least three 281 conditions. It must have an absorption coefficient close to the sample, negligible ACn content, and 282 small average particle size in order to be easily homogenised with the sample under study. In our 283 case, ZnO was used as internal standard. This compound was selected because its MAC value, 2 -1 284 50.34 cm /g, yields a linear attenuation coefficient, 285 cm , very similar to those of the analysed 285 cements. Furthermore, its particle size is small, approximately 0.5 m as determined by scanning 286 electron microscopy; its face-centred crystal structure gives a very simple pattern avoiding strong 287 overlapping with the diffraction lines of the studied cements; and a previous study [60] showed very 288 small, if any, ACn content. 289 A simple Rietveld refinement using the methodology explained in section 2.2.4.1 will yield a set of 290 weight fractions normalized to 100%. However in this case, in addition to the weight fractions of 291 the phases in the sample, the Rietveld refined weight fraction of the standard, Rst, is also obtained. It 292 should be kept in mind that the weight fraction added of the internal standard is precisely known, 293 Wst. If the sample contains ACn, Rst will be (much) larger than Wst. From this overestimation, the 294 overall ACn content is derived according to equation (5) [32]: 1- W 295 ACn = st / R st 4 10 % (5) 100Wst 13 296 Once the overall ACn content of the sample under study, ACn, is known, the initial RQPA can be 297 recalculated to yield the real sample phase contents. All details for these calculations have been 298 already reported [32]. Furthermore, the errors associated to this approach and the optimum amount 299 of standard has been recently discussed [61]. 300 3. Results and discussion. 301 3.1. Standard RQPA of Yeelimite-containing clinkers/cement. 302 Three commercial CSA clinkers (ALIPRE®, BELITH_CS10 and S.A.cement), one CSA cement 303 (CSA_trial) and two laboratory-prepared BCSA clinkers (BCSAF_B0 and BCSAF_B2) have been 304 analyzed by LXRPD. Table 5 reports the direct RQPA results (wt%) obtained for these samples 305 where Rietveld results were normalized to 100% of crystalline phases. These values were obtained 306 from the approach described in section 2.2.4.1, and hence, the presence of an ACn fraction is 307 neglected. Standard deviations are derived from three independent measurements (not the 308 mathematical errors from the Rietveld fits). These three analyses were carried out to different 309 portions of the samples for better averaging (i.e. not recording three patterns for the same sample). 310 Figures 1 to 6 show a selected range of the Rietveld plots for the six studied Yeelimite-containing 311 cements. The major peaks for each phase are labelled. 312 Several conclusions can be drawn from the phase analyses reported in Table 5. 313 I) Yeelimite, ideal stoichiometry Ca4Al6O12(SO4), is known to crystallise in the tectosilicate sodalite . 314 type structure, Na4Al3Si3O12 Cl. Replacement of chloride by sulfate and partial replacement of 315 sodium by calcium gives hauynite, Na3CaAl3Si3O12(SO4). Both sodalite and hauynite minerals are 316 cubic. However, some aluminates with sodalite structure are known to be orthorhombic, for 317 instance Ca4Al6O12(WO4) [62,63]. Therefore, both orthorhombic and cubic structural descriptions 318 have been included in the control file for the RQPA, see Table 3. It is noteworthy that five out of six 319 studied samples contained a mixture of orthorhombic and cubic sodalite type-structures. Only, 14 320 BCSAF_B2 sample showed just cubic Yeelimite. We speculate that this is due to the simultaneous 321 presence of Na, Fe and Si within cubic Yeelimite in BCSAF_B2. A deep synthetic and structural 322 study of cubic and orthorhombic C4A3S-type phases is in progress, including neutron powder 323 diffraction, and it will be reported elsewhere. 324 II) It is also important to identify the belite polymorph and its quantification. Borax addition fully 325 transform -belite in BCSAF_B0 to fully 'H-belite in BCSAF_B2, in complete agreement with a 326 previous report [60]. The mechanism for the borax-activation of belite has been very recently 327 unravel as a solid solution, Ca2-xNax(SiO4)1-x(BO3)x, has been proved and the crystal structure of 328 'H-Ca1.85Na0.15(SiO4)0.85(BO3)0.15 has been worked out [45]. It is also noteworthy that S.A.cement 329 has a high 'H-belite content. This can be justified with the elemental composition reported in Table 330 2, as its Na2O content is quite high, 1.4 wt%. Na2O is known to stabilise -forms of belite [64,65]. 331 III) CS quantified in ALIPRE®, S.A.cement and CSA_trial is the high temperature polymorph, 332 anhydrite-II [48]. So, this less reactive CS was likely produced during the clinkering process. It 333 should be noted that gypsum, bassanite and less-soluble anhydrite-II can be easily distinguished and 334 quantified by RQPA. However, bassanite and highly soluble anhydrite-III can only be distinguished 335 in especial experimental conditions [66] with high-quality laboratory X-ray powder diffraction data. 336 IV) The good accuracy of the analyses can be estimated by the comparison of the XRF results 337 (Table 2) and RQPA results (Table 5). RQPA showed the highest amount of periclase (MgO) for 338 BELITH_CS10, 2.2(2) wt%, and this is in full agreement with elemental analysis reported in Table 339 2, where this clinker showed the highest MgO content, 2.7 wt%. Furthermore, S.A.cement was the 340 second sample with the highest magnesium content determined by XRF, 1.5 wt%, and RQPA 341 showed the second highest periclase content, 1.1 wt%. We choose to compare magnesium oxide 342 contents because magnesium is little soluble in the Yeelimite structure. 15 343 V) The presence of ternesite (also known as sulfate-spurrite), C5S2S, is quite uncommon in CSA or 344 BCSA clinkers. However, CSA_trial has a high amount of ternesite, 16.2(5) wt%. This is likely due 345 to a very high SO3 dosage in the raw materials. XRF SO3 value for this cement, 16.7 wt%, is very 346 high even taken into account the ~14 wt% of gypsum added. Overall SO3 values range 347 approximately from 9 to 14 wt% for CSA clinkers and between 3 and 4 wt% for BCSA clinkers. 348 VI) Titanium is usually present in CSA and BCSA cements as it accompanies aluminium in 349 bauxites. High aluminium contents in CSA clinkers are linked to high titanium contents as shown in 350 Table 2. Consequently, lower aluminium contents in BCSA are linked to lower titanium contents. 351 Furthermore, titanium may replace aluminium in some phases but the solubility limits are exceeded 352 in CSA and BCSA clinkers. This is evident from the RQPA as the perovskite CaTiO3 phase 353 segregates. We have carried out the RQPA with this assumed stoichiometry, CaTiO3, however 354 further studies are needed in order to establish the stoichiometry of the perovksite phase as it is very 355 well known that this phase forms extensive solid solutions with transition metals. 356 Finally, selective dissolutions have been carried out for BCSAF_B0 and BCSAF_B2, see Figures 7 357 and 8. This work was carried out for a better characterisation of these samples. For instance, it can 358 be highlighted that the main peak of CT is strongly overlapped with the main peak of C3A and 359 merwinite, Ca3Mg(SiO4)2. Therefore, RQPA, itself, can not distinguish between these phases. 360 Figure 7 shows a small selected region of the Rietveld plots for BCSAF_B0 clinker plus the 361 aluminate and silicate residues. Figure 8 shows the same type of graphic for BCSAF_B2. The 362 Rietveld plot for the silicate residue of BCSAF_B0 is very informative as the diffraction peaks from 363 C4AF disappear but the diffraction peak at ~33.3º (2) is still present. Hence, this phase could be 364 pervoskite or merwinite but not C3A. The Rietveld refinements of the silicate residue indicated that 365 the fit with perovskite was better (lower R-factors) than that with merwinite. 16 366 Furthermore, a close analysis of the Rietveld plots of the residues indicates that the peaks widths in 367 the BCSAF_B2 are narrower than those in BCSAF_B0. For instance, the diffraction peaks from CT 368 and C4A3S in BCSAF_B2 aluminate fraction are narrower than those in the BCSAF_B0 aluminate 369 fraction, see Figure 8b and 7b, respectively. This behaviour is likely due to a better particle growth 370 when borax is added. In fact, scanning electron microscopy data (not shown) indicate that the 371 average particle sizes for BCSAF_B2 are larger than those of BCSAF_B0. However, the unit cell 372 values of some phases change between the two studied clinkers. Furthermore, these values also 373 slightly change between a clinker and the residues. So, the unit cell variations may also influence 374 the degree of overlapping and consequently, some peak widths. 375 3.2. Absolute RQPA of Yeelimite-containing clinkers/cement. 376 Table 6 shows the RPQA results (wt%) for the Yeelimite-containing samples including the ACn 377 contents employing the two methodologies previously described. The values obtained from 378 reflection geometry using an external standard (G-method) are given in the first row. The values 379 obtained from transmission geometry using ZnO as internal standard are given in the second row. In 380 both cases, standard deviations are derived from three independent measurements. 381 Three important conclusions can be drawn from the comparative study shown in Table 6. Firstly, 382 using the G-factor (previously obtained with an external standard, see Table 4), it allowed 383 measuring both the crystalline phases and the ACn contents. The ACn contents of CSA 384 clinkers/cements are similar to those found in OPC cements, ~ 10 wt% [30-32]. However, these 385 contents are much higher in BCSA clinkers, of the order of 25 wt%. We would like to highlight that 386 this measurement does not mean that there is about 25 wt% of amorphous/sub-cooled liquid in these 387 clinkers. These high values are likely due to the high concentration of impurities and defects in 388 belite. 17 389 Secondly, transmission powder diffraction data were also recorded for the same samples. An 390 alternative methodology is always advisable to show the appropriateness of data recording and data 391 analysis strategies. Furthermore, although the internal standard dilutes the phases in the samples, 392 ZnO was added to determine the overall ACn contents. Table 6 also reports the analytical results 393 obtained from this methodology. Overall, the same trend was obtained concerning the ACn 394 contents. CSA clinkers have ACn contents close to 10 wt% except for BELITH_CS10, which 395 essentially had a cero value. Furthermore, the BCSA clinkers displayed high ACn contents, ~ 25 396 wt%, in full agreement with those obtained with the G-method. 397 For the internal standard method, the reported uncertainties in Table 6 are those arising from the 398 average of three measurements. However, the uncertainties resulting from the amount of standard 399 used, 25 wt%, are not taken into account. Therefore, the standard deviations reported for the ACn 400 numbers are underestimated. Errors close to 3 wt% are more likely to occur, but they are very 401 difficult to quantify with precision. 402 Thirdly, a brief discussion on the results obtained by these two methods is worthy, see Table 6. For 403 four samples, S.A.cement, CSA_trial, BCSA_B0 and BCSAF_B2, the Rietveld quantitative phase 404 analysis values agree quite well. However, for ALIPRE® and BELITH_CS10, the results are not 405 that satisfactory. For ALIPRE®, the differences in the quantification of C4A3S-c, -belite and ACn 406 are 5.7, 4.3 and 10.3 wt%. Three times the standard deviations is commonly used for a good level of 407 confidence. So, the sum of 3 for the two analyses was calculated giving 3.0, 5.1 and 9.6 wt% for 408 C4A3S-c, -belite and ACn values, respectively. Therefore, the quantification of C4A3S-c for 409 ALIPRE® is well out of the limits. For BELITH_CS10, the differences in the quantification of 410 C4A3S-o, -belite and ACn are 4.3, 7.2 and 14.5 wt%, with the sum of 3 for the two analyses 411 giving 3.9, 3.9 and 5.7 wt%, respectively. In this case, the quantification of -belite and ACn does 18 412 not agree. We do not have a definitive answer for this behaviour but correlations of the phase scale 413 factors with the peak shape parameters may be likely playing a role. 414 Finally, it is worth to highlight the importance of having accurate structural description for every 415 phase in the cements to be analysed. This is more important for high-content phases, and it will be 416 illustrated for the RQPA of BCSAF_B2. If the ‗old‘ approximate crystal structure of 'H-C2S is 417 used [44], one Rietveld fit of the reflection data gave RWP=5.22% and RF('H-C2S)=7.24%. The 418 application of the G-method gave 'H-C2S and ACn contents of 35 and 33 wt%, respectively. If a 419 better structural description is used, 'H-Ca1.85Na0.15(SiO4)0.85(BO3)0.15 [45], then, the Rietveld fit of 420 the same pattern was better (lower disagreement factors): RWP=4.87% and RF('H-C2S)=5.72%. 421 This better fit gave a larger 'H-C2S scale factor (30.94 instead of 25.53) and therefore, the 'H-C2S 422 content was larger (40 wt%) and ACn content smaller, 28 wt%. So, the use of approximate crystal 423 structures give lower determined crystalline phase contents and higher ACn contents, as expected. 424 425 4. Conclusions. 426 Rietveld quantitative phase analyses of three commercially-available calcium sulfoaluminate 427 clinkers have been successfully carried out. In addition, two laboratory prepared iron-rich belite 428 calcium sulfoaluminate clinkers have been also studied. All commercial CSA clinkers contained 429 mixtures of orthorhombic and cubic Yeelimites. Only, the borax-activated BCSA clinker contained 430 just cubic-Yeelimite. Moreover borax addition transform -belite in BCSAF_B0 to fully ‘H-belite 431 in BCSAF_B2. Other accompanying phases have been quantified. It has been found a good 432 agreement between elemental compositions obtained by X-ray fluorescence and mineralogical 433 compositions obtained by Rietveld analysis of powder diffraction data as shown for MgO/periclase. 434 Selective dissolutions were employed to better characterise the iron-rich belite calcium 19 435 sulfoaluminate clinkers. Using this approach, every phase in the samples was firmly established. 436 Finally, the ACn contents of these materials were measured by both external and internal standard 437 methods. The agreement was fairly good for some cements but the variations for ALIPRE® and 438 BELITH_CS10 were larger than expected. Overall, the analyses showed that the commercial 439 calcium sulfoaluminate clinkers have ACn contents quite similar to those of OPCs, ~ 10 wt%. 440 Conversely, the ACn contents of the belite calcium sulfoaluminate clinkers were higher, ~ 25 wt%. 441 Acknowledgments 442 This work has been supported by Spanish Ministry of Science and Innovation through MAT2010- 443 16213 research grant, which is co-funded by FEDER. I.S. thanks a Ramón y Cajal fellowship, 444 RYC-2008-03523. 445 References 446 [1] A. Klein, Calciumaluminosulfate and expansive cements containing same, US Patent No. 3, 447 155, 526 (1963) 4 pp. 448 [2] Y. Wang, M. Su, The third cement series in China, World Cem. 25 (1994) 6-10. 449 [3] E.M. Gartner, Industrially interesting approaches to ―low- CO2‖ cements, Cem. Concr. Res. 34 450 (2004) 1489-1498. 451 [4] G.S. Li, G. Walenta, E.M. Gartner, Formation and hydration of low-CO2 cements based on 452 belite, calcium sulfoaluminate and calcium aluminoferrite, Proceedings of the 12th ICCC, Montreal, 453 Canada (2007) pp TH3-15.3. 454 [5] M.C.G. Juenger, F. Winnefeld, J.L. Provis, J.H. Ideker, Advances in alternative cementitious 455 binders, Cem. Concr. Res. 41 (2011) 1232-1243. 456 [6] Q. Zhou, N.B. Milestone, M. Hayes, An alternative to Portland cement for waste 457 encapsulation—the calcium sulfoaluminate cement system, J. Hazard. Mater. 136 (2006) 120–129. 20 458 [7] F.P. Glasser, L. Zhang, High-Performance Cement Matrices Based on Calcium 459 Sulphoaluminate-Belite Compositions, Cem. Concr. Res. 31 (2001) 1881-1886. 460 [8] J. Beretka, M. Marroccoli, N. Sherman, G.L. Valenti, The influence of C4A3S content and WS 461 ratio on the performance of calcium sulfoaluminate-based cements, Cem. Concr. Res. 26 (1996) 462 1673-1681. 463 [9] S. Sahu, J. Majling, Preparation of sulphoaluminate belite cement from fly ash, Cem. Concr. 464 Res. 24 (1994) 1065-1072. 465 [10] I. Odler, Special inorganic cements, Taylor and Francis Publisher. Cap. 4 (2000) 69-74. 466 [11] F. Winnefeld, S. Barlag, Calorimetric and thermogravimetric study on the influence of calcium 467 sulfate on the hydration of yeelimite, J. Therm. Anal. Calorim. 101 (2010) 949-957. 468 [12] S. Berger, C.C.D. Coumes, P. Le Bescop, D. Damidot, Influence of a thermal cycle at early age 469 on the hydration of calcium sulphoaluminate cements with variable gypsum contents, Cem. Concr. 470 Res. 41 (2011) 149–160. 471 [13] I.A. Chen, C.W. Hargis, M.C.G. Juenger, Understanding expansion in calcium sulfoaluminate- 472 belite cements, Cem. Concr. Res. 42 (2012) 51-60. 473 [14] L. Zhang, F.P. Glasser, Hydration of calcium sulfoaluminate cement at less than 24 h, Adv. 474 Cem. Res. 14 (2002) 141-155. 475 [15] G.S. Li, E.M. Gartner, High-belite sulfoaluminate clinker: fabrication process and binder 476 preparation, World Patent Application WO 2006/018569 A2. 477 [16] K. Quillin, Performance of belite-sulfoaluminate cements, Cem. Concr. Res. 31 (2001) 1341- 478 1349. 479 [17] I. Janotka, U. Krajci, S.C. Mojumdar, Performance of sulphoaluminate-belite cement with high 480 C4A3$ content, Ceram. Silik. 51 (2007) 74-81. 481 [18] D. Adolfsson, N. Menad, E. Viggh, B. Bjorkman, Hydraulic properties of sulphoaluminate 482 belite cement based on steelmaking slags, Adv. Cem. Res. 19 (2007) 133-138. 21 483 [19] J. Pera, J. Ambroise, New applications of calcium sulfoaluminate cement, Cem. Concr. Res. 34 484 (2004) 671-676. 485 [20] G. Walenta, C. Comparet, V. Morin, E. Gartner, Hydraulic binder based on sulfoaluminate 486 clinker and minerals additions, World Patent Application WO 2010/070215 A1 (2010). 487 [21] G. Walenta, E. Gartner, V. Morin, Additives for hydraulic binder based on iron-rich belite 488 calcium sulfoaluminate clinker, World Patent Application WO 2011/020958 A1 (2011). 489 [22] A. Wolter, Belite cements and low energy clinker, Cem. Inter. 3 (2005) 106-117. 490 [23] G.L. Valenti, M. Marroccoli, F. Montagnaro, M. Nobili, A. Telesca, Synthesis, hydration 491 properties and environmental friendly features of calcium sulfoaluminate cements, Proceedings of 492 the 12th International Congress of Cement Chemistry, Montreal (2007) W3 11.2. 493 [24] M.C Martín-Sedeño, A.J.M. Cuberos, A.G. De la Torre, G. Álvarez-Pinazo, L.M. Ordónez, M. 494 Gateshki, M.A.G. Aranda, Aluminum-rich belite sulfoaluminate cements: Clinkering and early age 495 hydration, Cem. Concr. Res. 40 (2010) 359–369. 496 [25] A.G. De la Torre, A.J.M. Cuberos, G. Alvarez-Pinazo, A. Cuesta, M.A.G. Aranda, In situ 497 powder diffraction study of belite sulfoaluminate clinkering, J. Synchr. Rad. 18 (2011) 506–514. 498 [26] J. Li, H. Ma, H. Zhao, Preparation of Sulphoaluminate-alite Composite Mineralogical Phase 499 Cement Clinker from High Alumina Fly Ash, Key Eng. Mat. 334-335 (2007) 421–424. 500 [27] H.M. Rietveld, A Profile Refinement Method for Nuclear and Magnetic Structures, J. Appl. 501 Cryst. 2 (1969) 65-71. 502 [28] D.L. Bish, S.A. Howard SA, Quantitative phase analysis using the Rietveld method, J. Appl. 503 Cryst. 21 (1988) 86-91. 504 [29] O. Pritula, L. Smrcok, B. Baumgartner, On reproducibility of Rietveld analysis of reference 505 Portland cement clinkers, Pow. Diffr. 18 (2003) 16-22. 506 [30] P.M. Suherman, A.V. Riessen, B. O‘connor, D. Li, D. Bolton, H. Fairhurst, Determination of 507 amorphous phase levels in Portland cement clinker, Pow. Diffr. 17 (2002) 178-185. 22 508 [31] P.S. Whitfield, L.D. Mitchell, Quantitative Rietveld analysis of the amorphous content in 509 cements and clinkers, J. Mater. Sci. 38 (2003) 4415-4421. 510 [32] A.G. De la Torre, S. Bruque, M.A.G. Aranda, Rietveld quantitative amorphous content 511 analysis, J. Appl. Cryst. 34 (2001) 196-202. 512 [33] J.P. Cline, R.B. Von Dree, R. Winburn, P.W. Stephens, J.J. Filliben, Addressing the 513 amorphous content issue in quantitative phase analysis: the certification of NIST standard reference 514 material 676a, Acta Cryst. Sect A 67 (2011) 357-367. 515 [34] B.H. O‘Connor, M.D. Raven, Application of the Rietveld refinement procedure in assaying 516 powdered mixtures, Pow. Diffr. 3 (1988) 2-6. 517 [35] D. Jansen, Ch. Stabler, F. Goetz-Neunhoeffer, S. Dittrich, J. Neubauer, Does Ordinary Portland 518 Cement contain amorphous phase? A quantitative study using an external standard method, Pow. 519 Diffr. 26 (2011) 31-38. 520 [36] D. Jansen, F. Goetz-Neunhoeffer, B. Lothenbach, J. Neubauer, The early hydration of Ordinary 521 Portland Cement (OPC): An approach comparing measured heat flow with calculated heat flow 522 from QXRD, Cem. Concr. Res. 42 (2012) 134-138. 523 [37] J. Wang, Hydration mechanism of cements based on low-CO2 clinkers containing belite, 524 ye‘elimite and calcium alumino-ferrite, PhD Thesis, University of Lille (2010). 525 [38] A.C. Larson, R.B. Von Dreele, General Structure Analysis System (GSAS), Los Alamos 526 National Laboratory Report LAUR (2000) pp 86-748. 527 [39] P. Thompson, D.E. Cox, J.B. Hasting, Rietveld refinement of Debye-Scherrer synchrotron X- 528 ray data from Al2O3, J. Appl. Cryst. 20 (1987) 79-83. 529 [40] L.W. Finger, D.E. Cox, A.P. Jephcoat, A correction for powder diffraction peak asymmetry 530 due to diaxial divergence, J. Appl. Cryst. 27 (1994) 892-900. 531 [41] W.A. Dollase, Correction of intensities for preferred orientation in powder diffractometry: 532 application of the March model, J. Appl. Cryst. 19 (1986) 267-272. 23 533 [42] N.J. Calos, C.H.L. Kennard, A.K. Whittaker, R.L.Davis, Structure of calcium aluminate 534 sulphate Ca4Al6O16S, J. Solid State Chem. 119 (1995) 1-7. 535 [43] H. Saalfeld, W.Depmeier, Silicon-free compounds with sodalite structure, Kristall und 536 Technik, 7 (1972) 229-233. 537 [44] W.G. Mumme, R.J. Hill, G. Bushnell-Wye, E.R. Segnit, Rietveld crystal structure refinement, 538 chemistry and calculated powder diffraction data for the polymorphs of dicalcium silicate and 539 related phases, N. Jb. Miner. Abh. 169 (1995) 35-68. 540 [45] A. Cuesta, E.R. Losilla; M.A.G. Aranda, A.G. De la Torre, Reactive belite stabilization 541 mechanisms by boron-bearing dopants, Cem. Concr. Res. 42 (2012) 598-606. 542 [46] A.A. Colville, S. Géller, The crystal structure of brownmillerite, Ca2FeAlO5, Acta Cryst. B27 543 (1971) 2311-2315. 544 [47] S. Sasaki, C.T. Prewitt, J.D.Bass, Orthorhombic perovskite CaTiO3 and CdTiO3: structure and 545 space group, Acta Cryst. C43 (1987) 1668-1674. 546 [48] A. Kirfel, G. Will, Charge density in anhydrite, CaSO4, from X-ray and neutron diffraction, 547 Acta Cryst. B36 (1980) 2881-2890. 548 [49] A.G. De la Torre, M.G. Lopez-Olmo, C. Alvarez-Rua, S. Garcia-Granda, M.A.G. Aranda, 549 Structure and microstructure of gypsum and its relevance to Rietveld quantitative phase analyses, 550 Pow. Diffr. 19 (2004) 240-246. 551 [50] S. Sasaki, K. Fujino, Y. Takeuchi, X-ray determination of electron-density distributions in 552 oxides, MgO, MnO, CoO, and NiO, and atomic scattering factors of their constituent atoms, Proc. 553 Jap. Acad. 55 (1979) 43-48. 554 [51] W. Hörkner, Hk. Müller-Buschbaum, Crystal-structure of CaAl2O4, Inorg. Nuclear Chem. 38 555 (1976) 983-984. 24 556 [52] A.G. De la Torre, S. Bruque, J. Campo, M.A.G. Aranda, The superstructure of C3S from 557 synchrotron and neutron powder diffraction and its role in quantitative phase analyses, Cem. Concr. 558 Res. 32 (2002) 1347-1356. 559 [53] S.J. Louisnathan, Refinement of the crystal structure of a natural gehlenite, Ca2Al(Al,Si)O7, 560 Can. Min. 10 (1971) 822-837. 561 [54] P.D. Brotherton, J.M. Epstein, M.W. Pryce, A.H. White, Crystal structure of calcium 562 sulphosilicate, Ca5(SiO4)2(SO4), Australian J. Chem. 27 (1974) 657-660. 563 [55] H. Effenberger, A. Kirfel, G. Wil, Studies of the electron-density distribution of dolomite, 564 CaMg(CO3)2, Tschermaks Mineralogische und Petrographische Mitteilungen, 31 (1983) 151-164. 565 [56] I.P. Swainson, , M.T. Dove, W.W.Schmahl, A. Putnis, Neutron Diffraction Study of the 566 Akermanite-Gehlenite Solid Solution Series, Phys. Chem. Min. 19 (1992) 185-195. 567 [57] V. Kahlenberg, G. Doersam, M. Wendschuh-Josties, R.X. Fischer, The crystal structure of 568 delta-(Na2Si2O5), J. Solid State Chem. 146 (1999) 380-386. 569 [58] E.N. Maslen, V.A. Streltsov, N.R. Streltsova, N. Ishizawa, Y. Satow, Synchrotron X-ray study 570 of the electron density in alpha-Al2O3, Acta Cryst. B49 (1993) 973-980. 571 [59] J. Albertsson, S.C. Abrahams, A. Kvick, Atomic displacement, anharmonic thermal vibration, 572 expansivity and pyroelectric coefficient thermal dependences in ZnO, Acta Cryst. B45 (1989) 34- 573 40. 574 [60] A.J.M. Cuberos, A.G. De la Torre, G. Álvarez-Pinazo, M.C. Martín-Sedeño, K. Schollbach, H. 575 Pöllmann, M.A.G. Aranda, Active Iron-Rich Belite Sulfoaluminate Cements: Clinkering and 576 Hydration, Environ. Sci. Technol. 44 (2010) 6855-6862. 577 [61] T. Westphal, T. Füllmann, H. Pöllmann, Rietveld quantification of amorphous portions with an 578 internal standard-mathematical consequences of the experimental approach, Pow. Diffr. 24 (2009) 579 239-243. 25 580 [62] W. Depmeier, Aluminate Sodalite Ca8[Al12O24](WO4)2 at Room Temperature, Acta Cryst. C40 581 (1984) 226-231. 582 [63] W. Depmeier, Structure of Cubic Aluminate Sodalite Ca8[Al12O24](WO4)2 in Comparison with 583 its Orthorhombic Phase and with Cubic Sr8[Al12O24](CrO4)2, Acta Cryst. B44 (1988) 201-207. 584 [64] K. Morsli, AG. de la Torre, S. Stober, A.J.M. Cuberos, M. Zahir, M.A.G. Aranda, Quantitative 585 Phase Analysis of Laboratory-Active Belite Clinkers by Synchrotron Powder Diffraction, J. Am. 586 Ceram. Soc. 90 (2007) 3205-3212. 587 [65] K. Morsli, AG. de la Torre, M. Zahir, M.A.G. Aranda, Mineralogical phase analysis of alkali 588 and sulfate bearing belite rich laboratory clinkers, Cem. Concr. Res. 37 (2007) 639-646. 589 [66] S. Seufert, C. Hesse, F. Goetz-Neunhoeffer, J. Neubauer, Discrimination of bassanite and 590 anhydrite III dehydrated from gypsum at different temperatures, Z. Kristallogr. Suppl. 30 (2009) 591 447-452. 592 593 594 Figure Captions 595 Figure 1. Selected range of the Rietveld plot for ALIPRE® clinker. Crosses are the experimental 596 scan, solid line is the calculated pattern and the bottom line is the difference curve. The major peaks 597 for each phase are labelled. 598 Figure 2. Selected range of the Rietveld plot for BELITH_CS10 clinker. Crosses are the 599 experimental scan, solid line is the calculated pattern and the bottom line is the difference curve. 600 The major peaks for each phase are labelled. 601 Figure 3. Selected range of the Rietveld plot for S.A.cement clinker. Crosses are the experimental 602 scan, solid line is the calculated pattern and the bottom line is the difference curve. The major peaks 603 for each phase are labelled. 26 604 Figure 4. Selected range of the Rietveld plot for CSA_trial cement. Crosses are the experimental 605 scan, solid line is the calculated pattern and the bottom line is the difference curve. The major peaks 606 for each phase are labelled. 607 Figure 5. Selected range of the Rietveld plot for BCSAF_B0 clinker. Crosses are the experimental 608 scan, solid line is the calculated pattern and the bottom line is the difference curve. The major peaks 609 for each phase are labelled. 610 Figure 6. Selected range of the Rietveld plot for BCSAF_B2 clinker. Crosses are the experimental 611 scan, solid line is the calculated pattern and the bottom line is the difference curve. The major peaks 612 for each phase are labelled. 613 Figure 7. Selected small range (30 – 36 º /2) of the Rietveld plots for: (a) BCSAF_B0 clinker, (b) 614 BCSAF_B0 aluminate residue, (c) BCSAF_B0 silicate residue. All details as in previous Rietveld 615 figures. 616 Figure 8. Selected small range (30 – 36 º /2) of the Rietveld plots for: (a) BCSAF_B2 clinker, (b) 617 BCSAF_B2 aluminate residue, (c) BCSAF_B2 silicate residue. All details as in previous Rietveld 618 figures. 619 620 27 Table 1. Raw materials employed for the preparation of BCSAF clinkers (expressed in grams). Limestone Kaolin Bauxite Gypsum Marl Borax BCSAF_B0 1796.30 281.03 519.53 227.51 209.78 - BCSAF_B2 1744.21 272.88 504.47 220.91 203.70 120.26 Table 2. Elemental composition, determined by XRF and expressed as oxide wt%, of the Yeelimite-containing clinkers. The mass attenuation coefficients (MAC) used in this study are also given in italics. 2 ALIPRE® BELITH_CS10 S.A.cement CSA_trial BCSAF_B0 BCSAF_B2 MAC (cm /g) CaO 41.59 41.86 44.10 45.59 51.75 50.99 120.47 Al2O3 33.64 33.85 27.30 20.93 18.78 17.03 30.91 SiO2 6.52 8.21 9.00 10.13 16.70 16.53 34.84 SO3 13.97 8.81 12.20 16.66 3.68 3.70 42.48 Fe2O3 0.89 2.37 2.60 3.63 6.72 6.28 220.77 # B2O3 - - - - 0.13 2.37 8.26 # Na2O 0.09 <0.08 1.40 0.18 0.10 1.00 24.28 K2O 0.39 0.25 0.30 0.31 0.34 0.33 116.82 MgO 0.68 2.73 1.50 1.26 0.99 0.97 27.88 TiO2 1.48 1.50 1.30 1.00 0.65 0.62 121.97 SrO 0.50 0.15 0.20 0.17 0.028 0.03 100.36 Cr2O3 - 0.017 - 0.02 0.028 0.023 176.40 MnO - 0.011 - 0.02 0.036 0.034 217.87 ZrO2 0.10 0.070 - 0.05 0.021 0.019 104.15 P2O5 0.16 0.13 0.10 0.04 0.055 0.059 38.59 2 MAC (cm /g) 73.81 75.96 78.56 82.31 92.00 89.28 - # B2O3 and Na2O contents were measured by ICP-MS. 28 Table 3. ICDD-PDF and ICSD collection codes for all phases used for Rietveld refinements. PDF-code ICSD code Ref. PDF-code ICSD code Ref. C4A3S-o 01-085-2210 80361 [42] M 01-071-1176 9863 [50] C4A3S-c 01-071-0969 9560 [43] CA 01-070-0134 260 [51] -C2S 01-086-0397 81095 [44] C3S 01-070-8632 94742 [52] -C2S 01-086-0398 81096 [44] C2AS 01-089-5917 87144 [53] ’-C2S 01-086-0399 81097 [44] C5S2S 01-070-1847 4332 [54] ’-C2S (act.) 01-086-0399 - [45] Dolomite 01-075-1711 31277 [55] C4AF 01-071-0667 9197 [46] Akermanite 01-079-2425 67691 [56] CT 01-078-1013 62149 [47] Na2Si2O5 01-089-8339 88662 [57] CS 01-072-0916 16382 [48] Al2O3 (standard) 01-081-2267 73725 [58] CSH2 00-033-0311 151692 [49] ZnO (standard) 01-079-0206 65120 [59] Table 4. Computed G factor and selected structural details for the alumina standard used. # # Rietveld scale factor from GSAS program 236.60 Sst (NIST Al2O3) 0.92748 -22 3 Cell volume 2.551·10 (cm ) 3 Density 3.998 (g/cm ) 2 MAC 30.91 (cm /g) -42 5 G-factor 7.46·10 (cm /wt%) # The individual phase scale factors provided in the GSAS program output 3 are multiplied by each phase volume (in Å ). So, this has to be taken into account when using equations 3 and 4. 29 Table 5. Direct RQPA results (wt%) for the Yeelimite-containing clinkers normalized to 100% of crystalline phases. Standard deviations are derived from three independent measurements (not the mathematical errors from the Rietveld fit). C4A3S-o C4A3S-c ’-C2S -C2S C4AF CT M C5S2S CSH2 CS C3S 1 ALIPRE® 51.0(7) 18.5(6) 9.4(3) 7.7(1) 3.5(1) 0.52(2) 9.0(4) 2 BELITH_CS10 40.1(9) 25.5(6) 16.0(2) 2.4(1) 9.3(1) 2.2(2) 3 S.A.cement 27.5(5) 28.7(6) 21.4(9) 9.7(4) 3.5(4) 1.1(1) 6.3(1) 4 CSA_trial 16.5(1.3) 23.6(7) 9.0(9) 4.8(2) 16.2(5) 13.7(4) 8.5(2) 5.9(5) 5 BCSAF_B0 14.6(1.1) 13.5(1.2) 48.7(6) 14.9(2) 1.3(2) BCSAF_B2 31.1(1.7) 56.7(1.8) 10.1(6) 2.1(2) 2 Also contains 4.6(1) wt% of akermanite. 3 Also contains 1.9(1) wt% of CA. 4 Also contains 1.8(7) wt% of dolomite. 5 Also contains 2.6(5) wt% of -C2S and 4.4(2) wt% of C2AS. 30 Table 6. RQPA results (wt%) for the Yeelimite-containing clinkers including the overall amorphous plus not-quantified crystalline phase(s) content. The values obtained from reflection geometry using an external standard (G-method) are given in the first row. The values obtained from transmission geometry using ZnO as internal standard are given in the second row (italics). Standard deviations are derived from three independent measurements (not the mathematical errors from the Rietveld fit). # C4A3S-o C4A3S-c ’-C2S -C2S C4AF CT M C5S2S CSH2 CS C3S ACn 1 ALIPRE® 42.0(9) 15.3(5) 7.7(2) 6.4(1) 2.9(1) 0.43(1) 7.5(4) 17.5(1.4) 41.0(8) 21.0(5) 7.6(2) 10.7(1.6) 3.0(2) 0.5(2) 8.2(1) 7.2(1.8) 2 BELITH_CS10 35.8(4) 22.8(3) 14.3(3) 2.1(1) 8.3(2) 2.0(2) 10.6(8) 40.1(9) 23.0(9) 21.5(1.0) 2.1(4) 7.9(1) 2.1(1) -3.9(1.1) 3 S.A.cement 24.2(6) 25.3(9) 18.8(4) 8.6(5) 3.1(4) 0.92(2) 5.6(2) 11.9(1.7) 23.0(7) 27.2(6) 17.1(3) 8.8(6) 2.9(1) 0.7(1) 6.1(1) 13.5(6) 4 CSA_trial 14.6(7) 21.2(1.0) 8.0(1.1) 4.3(3) 14.4(8) 12.2(7) 7.6(1) 5.3(6) 10.8(2.9) 14.3(6) 20.7(8) 9.0(6) 3.4(2) 13.0(1) 13.3(3) 7.5(2) 6.0(6) 12.3(1.4) 5 BCSAF_B0 10.9(1.0) 10.0(8) 36.2(1.3) 11.1(2) 1.0(1) 25.5(2.1) 10.2(7) 8.8(6) 33.3(1) 12.9(3) 0.6(2) 26.1(4) BCSAF_B2 22.5(1.6) 40.9(1.0) 7.3(4) 1.5(2) 27.7(1.2) 22.1(3) 41.9(4) 10.3(2) 0.9(2) 24.9(9) # ACn stands for amorphous plus not-quantified crystalline phase(s) which includes misfitting problems and not-computed phase(s). 1 Also contains: 0.4(1) wt% Na2Si2O5. 0.8(3) wt% Na2Si2O5. 2 Also contains: 4.1(1) wt% akermanite. 7.3(1) wt% akermanite. 3 Also contains 1.6(1) wt% CA. 0.8(2) wt% CA 4 Also contains 1.6(5) wt% dolomite. 1.0(4) wt% dolomite 5 Also contains 1.9(4) wt% -C2S and 3.3(2) wt% C2AS. 1.5(2) wt% -C2S and 6.7(3) wt% C2AS. 31 Figure(s) R7_Alipre Hist 1 Lambda 1.5406 A, L-S cycle 879 Obsd. and Diff. Profiles ALIPRE® C4A3S-o β-C2S C4A3S-c CS α’-C2S CT * * 20.0 25.0 30.0 35.0 40.0 45.0 2-Theta, deg Figure 1 Counts X10E 4 -1.0 0.0 1.0 2.0 3.0 2_CS10 Hist 1 Lambda 1.5406 A, L-S cycle 704 Obsd. and Diff. Profiles BELITH_CS10 C4A3S-o CT * C4A3S-c M β-C2S * 20.0 25.0 30.0 35.0 40.0 45.0 2-Theta, deg Figure 2 Counts X10E 4 -1.0 0.0 1.0 2.0 3.0 4_SA_Cement_alfa&beta Hist 1 Lambda 1.5406 A, L-S cycle 757 Obsd. and Diff. Profiles S.A.cement C4A3S-o β-C2S C4A3S-c CS α’-C2S CT * * 20.0 25.0 30.0 35.0 40.0 45.0 2-Theta, deg Figure 3 Counts X10E 4 -1.0 0.0 1.0 2.0 3.0 RR3_Dycker Hist 1 Lambda 1.5406 A, L-S cycle 347 Obsd. and Diff. Profiles CSA_trial C4A3S-o CS C4A3S-c CT * β-C2S C5S2S CSH2 * 20.0 25.0 30.0 35.0 40.0 45.0 2-Theta, deg Figure 4 Counts X10E 4 -0.5 0.0 0.5 1.0 1.5 5_BCSAF_B0 Hist 1 Lambda 1.5406 A, L-S cycle 479 Obsd. and Diff. Profiles BCSAF_B0 C4A3S-o C4AF C4A3S-c C2AS β-C2S γ-C2S 20.0 25.0 30.0 35.0 40.0 45.0 2-Theta, deg Figure 5 Counts X10E 4 0.0 0.5 1.0 RR6_BCSAF_B2 Hist 1 Lambda 1.5406 A, L-S cycle 581 Obsd. and Diff. Profiles BCSAF_B2 C4A3S-c C4AF α’-C2S CT * * 20.0 25.0 30.0 35.0 40.0 45.0 2-Theta, deg Figure 6 Counts X10E 4 0.0 0.5 1.0 5_BCSAF_B0 Hist 1 Lambda 1.5406 A, L-S cycle 483 Obsd. and Diff. Profiles (a) clinker Residuo_metanol-salicilico_B0_CT Hist 1 Lambda 1.5406 A, L-S cycle 512 Obsd. and Diff. Profiles 30.0 31.0 32.0 33.0 34.0 35.0 36.0 2-Theta, deg C4A3S-o C4AF (b) C 4A3S-c C2AS aluminates β-C2S CT * * Residuo_B0_KOH_CT Hist 1 Lambda 1.5406 A, L-S cycle 611 Obsd. and Diff. Profiles 30.0 31.0 32.0 33.0 34.0 35.0 36.0 2-Theta, deg (c) silicates * 30.0 31.0 32.0 33.0 34.0 35.0 36.0 Figure 7 2-Theta, deg Counts X10E 3 Counts X10E 3 Counts X10E 3 -2.0 0.0 2.0 4.0 6.0 0.0 2.0 4.0 6.0 8.0 0.0 2.0 4.0 6_BCSAF_B2 Hist 1 Lambda 1.5406 A, L-S cycle 556 Obsd. and Diff. Profiles * (a) clinker Residuo_Met_Sal_B2_CT Hist 1 Lambda 1.5406 A, L-S cycle 348 Obsd. and Diff. Profiles 30.0 31.0 32.0 33.0 34.0 35.0 36.0 2-Theta, deg C4A3S-c C4AF (b) α ’-C2S CT * aluminates C2AS * Residuo_KOH_B2_CT Hist 1 Lambda 1.5406 A, L-S cycle 888 Obsd. and Diff. Profiles 30.0 31.0 32.0 33.0 34.0 35.0 36.0 2-Theta, deg * (c) silicates Figure 8 30.0 31.0 32.0 33.0 34.0 35.0 36.0 2-Theta, deg Counts X10E 3 Counts X10E 4 Counts X10E 3 -2.0 0.0 2.0 4.0 6.0 8.0 0.0 0.5 1.0 0.0 2.0 4.0 6.0