Rietveld Quantitative Phase Analysis Research Articles

The existence of amorphous phase in Portland cements: Physical factors affecting Rietveld quantitative phase analysis

Rietveld quantitative phase analysis has become a widespread tool for the characterization of Portland cement, both for research and production control purposes. One of the major remaining points of debate is whether Portland cements contain amorphous content or not. This paper presents detailed analyses of the amorphous phase contents in a set of commercial Portland cements, clinker, synthetic alite and limestone by Rietveld refinement of X-ray powder diffraction measurements using both external and internal standard methods. A systematic study showed that the sample preparation and comminution procedure is closely linked to the calculated amorphous contents. Particle size reduction by wet-grinding lowered the calculated amorphous contents to insignificant quantities for all materials studied. No amorphous content was identified in the final analysis of the Portland cements under investigation.

The Baetican workshops: a starting point to study Terra Sigillata Hispanica

Terra Sigillata Hispanica (TSH) was a Roman pottery easily recognized by its characteristic intense red color. It was produced in several workshops in the Iberian Peninsula. Seven of them were placed within the Baetica province. Here, we report a full characterization of a series of 35 TSH samples from the known Baetican centers. Additionally, two samples recovered from Caserio Silverio Mayorga (Antequera, Malaga), a possible eighth production center, and another sample with an unpublished stamp (reading ‘NOMO’) are also studied. The main employed techniques were stereomicroscopic examination, elemental analysis by WDXRF, Rietveld quantitative phase analysis from laboratory XRPD, including amorphous quantification by the innovative G-factor approach and, finally, SEM-EDX for paste-microstructure and slip characterization. The results rule out Caserio Silverio Mayorga as a TSH production center. The stamped sample is not related to Alameda TSH, and it is likely from La Rioja. Chemical data analysis allows workshop separation when used with macroscopic examination. The mineralogical data show a wide range of variation in amorphous content (24–68 wt%), and also allow firing temperature estimation (900–1000 °C). The SEM-EDX study highlights the markedly thicker slips of Andujar productions (20–40 μm), made with c. 0.1 μm particles, compared to the rest of the workshops (≈10 μm).

Effect of substitution of lime stone in CPJ45 by Jorf Lasfer fly and bottom ash on the hydration of cement and on the mechanical proprieties of mortar

The study undertaken in this work indicates that it is possible to exploit the industrial by products such as fly ash and bottom ash from the combustion of coal in Jorf lasfar thermal power and valorize them as additive in the construction materials. Because in addition to their poozolanic activity, these ashes have technical, economical and ecological compelling interests.In this work we have studied the effects of substitution of limestone in the CPJ45 cement by fly ash or bottom ash on the mechanical properties of prepared mortars, on the grinding time and on the hydration of the new cements.Different analysis techniques were undertaken to determine the physico-chemical characteristics of the starting materials.X-ray fluorescence (XRF) had permitted the classification of fly ash and bottom ash in the class F from their levels on major oxides. Rietveld quantitative phase analysis (RQPA) allowed us to compare the percentages of clinker phases with that calculated with bogue formulas. The result showed that the values found by RQPA of C 3 S and C 3 A were much higher than those calculated, while for the C 2 S the values given by RQPA were much lower.The isothermal conduction micro calorimeter was used to measure the heat evolution during the hydration of the cements prepared. We noticed that the additions of fly ash or bottom ash have accelerated the hydration of C 3 A and have delayed that of C 3 S.The tests performed by substituting limestone in CPJ 45 by different proportions of fly ash or bottom ash have shown that the effect of these ashes on the mechanical properties of cement CPJ 45 . We have observed that the 28days mechanical strengths of the mortar went for a maximum with the substitution of lime stone by 6% of fly ash and 7% of bottom ash;We have also observed that increasing the amount of substitution of lime stone by fly ash had decreased the grinding time and had eliminated the clogging of the cement on the mill balls.

The Effect of Mg on Slag Reactivity in Blended Cements

Blast-furnace slags are widely used as supplementary cementitious materials in blended cements because of their relatively high reactivity. This study describes the effect of substituting Ca by Mg on the reactivity of synthetic glass with similar composition to slags, keeping the basicity ratio constant. The glass reactivity was assessed using a multi-technique approach including dissolution rate experiments at high dilution, calorimetry, X-ray diffraction combined with Rietveld quantitative phase analysis and electron microscopy image analysis of blended cement pastes. The effect of glass hydration on the hydration product assemblage was assessed by comparing experimental data to thermodynamic modelling. The results show that reactivity was not affected significantly by Ca by Mg substitution at constant basicity. The relative reactivities from the dissolution experiments, calorimetry and image analysis are in agreement and show a dependence of reactivity on basicity but not on Mg content. The release of Mg from the glasses led to the through-solution precipitation of hydrotalcite-like hydration products. Under the high pH conditions studied, there was no indication of incongruent glass dissolution or the formation of a leached passivating layer. The experimental results on changes in the cement hydration product assemblage by glass addition were supported by thermodynamic modelling and generally show an increase in calcium–aluminosilicate–hydrate, AFm, and hydrotalcite-type reaction products.

Quantitative Mineralogical Characterization of Karst Bauxite Deposits in the Southern Apennines, Italy

The southern Italian karst bauxite deposits occur at a Late Cretaceous hiatus on a Bahamian-type carbonate platform succession cropping out in the southern Apennines, and are mainly located in the Abruzzi Mountains, in Apulia (Gargano peninsula and Murge area), and in Campania. The bauxites of southern Italy are presently uneconomic, but can be considered as a model analogue for economic karst bauxite ores. The texture of the bauxite deposits is mainly oolitic to pisolitic but can also be arenitic-conglomeratic, suggesting reworking of evolved lateritic soils. The minerals boehmite and hematite are more abundant in the ooids, whereas kaolinite is found at high levels in the groundmass, and titanium oxides are also present. Furthermore, small amounts of rare earth elements have been detected in most of the bauxite occurrences. Scanning electron microscopy with energy dispersive spectrometry (SEM-EDS) and geochemical analyses on several of the deposits confirmed the diagenetic texture of the bauxite, and provided an estimate of the mineralogy of the different components and their chemical composition. The mineralogical and petrographic characteristics of bauxite are crucial for the Bayer process and can influence its economic evaluation: both the particle size distribution in the ore and the presence of reactive silica phases associated with Ti and Fe oxides can reduce the efficiency of processing. Quantitative analyses combining different methods (X-ray diffraction [XRD]-Rietveld quantitative phase analysis [QPA] and QEMSCAN ® ) have been carried out on a limited number of samples from two of the bauxite districts of the Campania region: the Matese Mountains and the Caserta province. QEMSCAN ® analysis allowed a more rapid quantification of mineralogy (including trace detrital phases) and assessment of the individual textural characteristics of the bauxite lithotypes, showing a detailed image of the distribution of economic and noneconomic minerals and their intergrowths. This methodology can augment or replace other time-consuming quantitative phase analyses for mineralogical studies of bauxites, provided that the species identification protocol (SIP) database has been carefully validated by preliminary use of XRD and SEM-EDS. Both XRD (QPA) and QEMSCAN ® analytical techniques can be complementary for bauxite ore evaluation, and a very powerful tool for exploitation and mineral processing.

Quantitative analysis of turbostratically disordered nontronite with a supercell model calibrated by the PONKCS method

Two calibration-based quantitative X-ray diffraction (XRD) models for turbostratically disordered Bulong nontronite, the PONKCS (partial or no known crystal structure) approach and the supercell structural model, were compared in terms of the accuracy and refinement error from Rietveld quantitative phase analysis. The PONKCS approach achieved improved nontronite quantitative results with synchrotron diffraction patterns compared with those achieved with laboratory XRD data as a result of better data quality and the use of Debye–Scherrer geometry with significantly reduced preferred orientation effects. The introduction of a peak shape modifier (spherical harmonics) to correct the quantification result is mainly useful for laboratory XRD patterns containing nontronite collected from Bragg–Brentano geometry with appreciable preferred orientation effects. A novel calibration approach for the nontronite supercell model was developed, based on the Rietveld quantitative formula in theTOPASsymbolic computation system. The calibrated supercell model achieved better accuracy (deviation within 1 wt%) and lower refinement error than the PONKCS approach because the physically based description of turbostratic disorder requires fewer refinable parameters than the PONKCS approach. The drawbacks and limitations of the supercell approach are also discussed.

Utilization of phosphate fertilizer industry waste for belite–ferroaluminate cement production

Phosphogypsum (PG) and pyrite cinder (PC) are phosphate fertilizer industry wastes. At present, the utilization of PG and PC is limited, their stockpiling brings about serious environmental problems. We studied the manufacturing technique for producing belite–ferroaluminate cement utilizing of PG and PC as raw materials instead of natural materials. The mechanical properties, mineral composition and microstructure of the resulting cement clinker were investigated using X-ray powder diffraction (XRD) with Rietveld quantitative phase analysis, scanning electron microscope (SEM), etc. We found that burning at 1250°C for 60min was suitable for clinker production. The effect of natural gypsum (NG) content on setting time, heat evolution, compressive strength, hydration products of cements were also investigated. The results show that setting time of cement depends much on NG content. The early hydration accelerates with NG content increasing. The effect of NG content on compressive strength at different curing age is variable. NG content in cement is also an important factor in the hydration products.

Rietveld quantitative phase analysis of Yeelimite-containing cements

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 ~10wt.%. Conversely, the unaccounted contents for BCSA clinkers were higher, ~25wt.%.

Rheological and hydration characterization of calcium sulfoaluminate cement pastes

Calcium sulfoaluminate (CSA) cements are currently receiving a lot of attention because their manufacture produces less CO2 than ordinary Portland cement (OPC). However, it is essential to understand all parameters which may affect the hydration processes. This work deals with the study of the effect of several parameters, such as superplasticizer (SP), gypsum contents (10, 20 and 30 wt.%) and w/c ratio (0.4 and 0.5), on the properties of CSA pastes during early hydration. This characterization has been performed through rheological studies, Rietveld quantitative phase analysis of measured X-ray diffraction patterns, thermal analysis and mercury porosimetry for pastes, and by compressive strength measurements for mortars. The effect of the used SP on the rheological properties has been established. Its addition makes little difference to the amount of ettringite formed but strongly decreases the large pore fraction in the pastes. Furthermore, the SP role on compressive strength is variable, as it increases the values for mortars containing 30 wt.% gypsum but decreases the strengths for mortars containing 10 wt.% gypsum.

Understanding the mechanism and kinetics of pentlandite oxidation in extractive pyrometallurgy of nickel

Pentlandite oxidation behavior in the temperature range 530–600°C was investigated by microscopic and kinetic methods. A clear four-step reaction sequence was identified through monitoring the reaction progress by Rietveld quantitative phase analysis of quenched samples. The first step involves the transformation of pentlandite to monosulfide solid solution (mss), (Fe,Ni)S. This is followed by the transformation from mss to α-NiS in the second step, the oxidation from Fe3O4 to Fe2O3 in the third step, and the oxidation of α-NiS to NiO in the final step. Avrami/Arrhenius analysis indicated rapid transformation of pentlandite to mss with rate constant increasing from 3.8×10−4s−1 at 530°C to 2.1×10−3s−1 at 600°C and an activation energy of 140kJmol−1; the rate constant for the transformation from mss to α-NiS increases from 6.7×10−5s−1 at 530°C to 4.4×10−4s−1 at 600°C with an activation energy of 151kJmol−1, and for the oxidation from Fe3O4 to Fe2O3 increases from 3.2×10−5s−1 at 530°C to 1.7×10−4s−1 at 600°C with an activation energy of 127kJmol−1. Such clear reaction mechanism and the associated kinetic data can be applied to optimize the operation conditions in industrial rosters and flash smelters to improve process efficiency and Ni recovery.

Modal Analysis of Montmorillonite in Bentonites Using Phase Mixing Equation

Based on the mass balance principle, mineral contents of the bentonites from Yangxian of Shaanxi province, Queshan of Henan province, and Chifeng of the Inner Mongolia Autonomous Region were estimated by resolving the Phase Mixing Equation constructed from the data of X-ray diffraction, microprobe analysis of montmorillonite grains, and chemical anaysis of the bentonites. The crystal formulas of montmorillonite in the bentonites were calculated based on the anion hydrogen equivalent method. The cell lattice constants of the principal minerals in the bentonites were calculated with a FORTRAN90 program CELLSR. When compared with both methods of the methylene blue absorption and XRD Rietveld quantitative phase analysis, the Phase Mixing Equation was confirmed to be the most effective modal analysis method for determing content of montmorillonite in bentonites with several minerals coexisted.

Quantitative X-ray Rietveld analysis of metallic aluminum content in nano-aluminum powders

Accurate analysis of the content of metal aluminum (Al) in nano-Al powders is a difficult task due to the high reactivity of nano-Al powders. Here, the X-ray Rietveld quantitative phase analysis (QPA) method was applied to analyze the content of metal aluminum in nano-Al powders produced by three methods. A good agreement between the observed and calculated diffraction pattern was obtained and the conventional Rietveld factors (R p, R wp and GOF) converged to satisfactory values, which suggested that Al content was evaluated accurately. At the same time, the mixture sample of 89.77 wt.% micro-Al + 10.23 wt.% α-Al 2O 3 was study and the fitting pattern and R factors were satisfactory, which further verified the reliability of the X-ray Rietveld QPA method.

Preparation and characterization of nanocomposites in system as: SnO2–xTiO2 (where x = 25, 50 and 75 mol%)

Nanocomposite samples containing various molar compositions of tin and titanium oxides were synthesized by a sol–gel method using octadecylamine as controlling template agent. The structural and the crystalline features of the samples were investigated with Fourier Transformer Infra-red, X-ray diffraction, Transmission electron microscope (TEM) where the surface area was estimated by BET analysis. The crystalline parameters and the particle size were estimated by Rietveld quantitative phase analysis. It is interesting to mention that a reduction in the lattice parameters was detected upon introduction of various molar compositions of titanium oxide revealing that a part of titania is incorporated into the SnO2 lattice forming Ti1−xSnxO2 solid solution. The quantitative analysis claims that part of titanium oxide is incorporated substitutionally in the crystal lattice of SnO2, forming a solid solution and other parts are either segregated as separate rutile titania phase or dispersed as amorphous phase on the grain boundary of SnO2. The results show a remarkable reduction in particle size from 42 to 5 nm and increasing in the specific surface area up to 176 m2/g upon introduction of various content of titania implying the role of titania particles in preventing SnO2 crystallites from further growing up during the progress of calcination. TEM images show that pure tin oxide particles arranged in large aggregation in wormhole like structure, while the existence of titanium oxide are successfully creates spherical nanoparticles system organized in a definite structure. The optical absorbance spectra indicate a red shift and band gap narrowing upon introduction of titania which increase with increasing in titania contents.

A large volume cell for in situ neutron diffraction studies of hydrothermal crystallizations

A hydrothermal cell with 320 ml internal volume has been designed and constructed for in situ neutron diffraction studies of hydrothermal crystallizations. The cell design adopts a dumbbell configuration assembled with standard commercial stainless steel components and a zero-scattering Ti-Zr alloy sample compartment. The fluid movement and heat transfer are simply driven by natural convection due to the natural temperature gradient along the fluid path, so that the temperature at the sample compartment can be stably sustained by heating the fluid in the bottom fluid reservoir. The cell can operate at temperatures up to 300 °C and pressures up to 90 bars and is suitable for studying reactions requiring a large volume of hydrothermal fluid to damp out the negative effect from the change of fluid composition during the course of the reactions. The capability of the cell was demonstrated by a hydrothermal phase transformation investigation from leucite (KAlSi(2)O(6)) to analcime (NaAlSi(2)O(6)⋅H(2)O) at 210 °C on the high intensity powder diffractometer Wombat in ANSTO. The kinetics of the transformation has been resolved by collecting diffraction patterns every 10 min followed by Rietveld quantitative phase analysis. The classical Avrami/Arrhenius analysis gives an activation energy of 82.3±1.1 kJ mol(-1). Estimations of the reaction rate under natural environments by extrapolations agree well with petrological observations.

Early age hydration and pozzolanic reaction in natural zeolite blended cements: Reaction kinetics and products by in situ synchrotron X-ray powder diffraction

The in situ early-age hydration and pozzolanic reaction in cements blended with natural zeolites were investigated by time-resolved synchrotron X-ray powder diffraction with Rietveld quantitative phase analysis. Chabazite and Na-, K-, and Ca-exchanged clinoptilolite materials were mixed with Portland cement in a 3:7 weight ratio and hydrated in situ at 40 °C. The evolution of phase contents showed that the addition of natural zeolites accelerates the onset of C 3S hydration and precipitation of CH and AFt. Kinetic analysis of the consumption of C 3S indicates that the enveloping C–S–H layer is thinner and/or less dense in the presence of alkali-exchanged clinoptilolite pozzolans. The zeolite pozzolanic activity is interpreted to depend on the zeolite exchangeable cation content and on the crystallinity. The addition of natural zeolites alters the structural evolution of the C–S–H product. Longer silicate chains and a lower C/S ratio are deduced from the evolution of the C–S–H b-cell parameter.

Aluminum-rich belite sulfoaluminate cements: Clinkering and early age hydration

Belite sulfoaluminate (BSA) cements have been proposed as environmentally friendly building materials, as their production may release up to 35% less CO{sub 2} into the atmosphere when compared to ordinary Portland cements. Here, we discuss the laboratory production of three aluminum-rich BSA clinkers with nominal mineralogical compositions in the range C{sub 2}S (50-60%), C{sub 4}A{sub 3}$$ (20-30%), CA (10%) and C{sub 12}A{sub 7} (10%). Using thermogravimetry, differential thermal analysis, high temperature microscopy, and X-ray powder diffraction with Rietveld quantitative phase analysis, we found that burning for 15 min at 1350 deg. C was the optimal procedure, in these experimental conditions, for obtaining the highest amount of C{sub 4}A{sub 3}$$, i.e. a value as close as possible to the nominal composition. Under these experimental conditions, three different BSA clinkers, nominally with 20, 30 and 30 wt.% of C{sub 4}A{sub 3}$$, had 19.6, 27.1 and 27.7 wt.%, C{sub 4}A{sub 3}$$ respectively, as determined by Rietveld analysis. We also studied the complex hydration process of BSA cements prepared by mixing BSA clinkers and gypsum. We present a methodology to establish the phase assemblage evolution of BSA cement pastes with time, including amorphous phases and free water. The methodology is based on Rietveld quantitative phase analysis of synchrotron and laboratory X-ray powder diffraction data coupled with chemical constraints. A parallel calorimetric study is also reported. It is shown that the beta-C{sub 2}S phase is more reactive in aluminum-rich BSA cements than in standard belite cements. On the other hand, C{sub 4}A{sub 3}$ reacts faster than the belite phases. The gypsum ratio in the cement is also shown to be an important factor in the phase evolution.

Comprehensive phase characterization of crystalline and amorphous phases of a Class F fly ash

A comprehensive approach to qualitative and quantitative characterization of crystalline and amorphous constituent phases of a largely heterogeneous Class F fly ash is presented. Traditionally, fly ash composition is expressed as bulk elemental oxide content, generally determined by X-ray fluorescence spectroscopy. However, such analysis does not discern between relatively inert crystalline phases and highly reactive amorphous phases of similar elemental composition. X-ray diffraction was used to identify the crystalline phases present in the fly ash, and the Rietveld quantitative phase analysis method was applied to determine the relative proportion of each of these phases. A synergistic method of X-ray powder diffraction, scanning electron microscopy, energy dispersive spectroscopy, and multispectral image analysis was developed to identify and quantify the amorphous phases present in the fly ash.

Round robin on Rietveld quantitative phase analysis of Portland cements

Interlaboratory studies on the precision and accuracy of Rietveld quantitative phase analysis (R-QPA) of mixtures of crystalline phases have already been carried out. However, cement-related materials are samples of variable complexity, ranging from three phases in white Portland clinkers to more than eight phases in grey cements, that need to be specifically investigated. Here, the results are reported from a round robin on the R-QPA of cement-related materials from laboratories with experience in this type of analysis. The aim of the work was to evaluate the levels of precision and accuracy associated with Portland clinkers and cements. Two sets of samples have been investigated, artificial mixtures and commercial samples. Artificial mixtures were prepared by mixing (weighing) synthesized single-crystalline phases in the appropriate proportions: (i) white clinker (Ca3SiO5, Ca2SiO4and Ca3Al2O6) and (ii) grey cement (Ca3SiO5, Ca2SiO4, Ca3Al2O6, Ca4Al2Fe2O10, CaCO3and CaSO4·2H2O). These two samples were used to assess the accuracy and uncertainty of the procedure, as an expected mineralogical phase fraction, the `true mineralogical percentage', is available under the assumption of negligible non-diffracting contents. In order to assess the validity and limitations of the Rietveld-based approach for cement materials, three commercial samples were measured: (i) white Portland clinker, (ii) grey Portland clinker and (iii) a type-I grey Portland cement. The samples studied have been chosen in order to cover most of the different typologies of binders. Reproducibilities and general uncertainty values, with a level of confidence of 95%, are reported and discussed.

Characterisation of various Jamaican bauxite ores by quantitative Rietveld X-ray powder diffraction and 57Fe Mössbauer spectroscopy

The characterisation of bauxite ores, in particular, the iron mineralogy, is critical when determining their processability. In this study, various Jamaican bauxite ores have been characterised by X-ray powder diffraction (XRD) utilising Rietveld quantitative phase analysis, and Mössbauer spectroscopy. The only forms of iron minerals found were crystalline hematite and crystalline alumino-goethite of relatively small crystallite size. The results obtained by XRD and Mössbauer spectroscopy were found to complement each other well, suggesting that for these samples, there is no indication of an appreciable amorphous iron phase present.

Crystal structure of low magnesium-content alite: Application to Rietveld quantitative phase analysis

Five members of tricalcium silicate solid solution, Ca 3 − x − y Mg x Al y (Si 1 − y Al y )O 5, have been prepared. T 1, T 3 and M 3 forms have been identified by X-ray powder diffraction, but pure M 1 form was not stabilized. The crystal structure of a sample nominally Ca 2.96Mg 0.03Al 0.01(Si 0.99Al 0.01)O 5 has been studied by a joint Rietveld refinement using strictly monochromatic laboratory X-ray and neutron powder diffraction data, with soft constraints of interatomic distances. The crystal structure of this alite is a T 3 form with a triclinic cell, space group P 1̄1­, of dimensions a = 11.6389(2) Å, b = 14.1716(3) Å, c = 13.6434(3) Å, α = 104.982(2)°, β = 94.622(1)°, γ = 90.107(2)° and V/ Z = 120.346(6) Å 3. Laboratory and commercial clinkers were studied by synchrotron X-ray powder diffraction and the Rietveld method. The reported T 3 structure for alite fits properly a variety of laboratory Portland clinkers with low magnesium contents. The alite refined volume(s) ( V/ Z) is useful to predict the magnesium oxide content of a clinker and the alite-type. Thus, a refined V/Z value between 121.0 and 120.3 Å 3 should contain up to ~ 1.0 wt.% of MgO, being T 3 type. If refined C 3S V/Z is smaller than ~ 119.8 Å 3 the clinker may contain more than ~ 2.1 wt.% of MgO with alite as M 3. For intermediate magnesium (and sulfur) contents, alites phase coexistence may be detected by using strictly monochromatic laboratory or synchrotron X-ray powder diffraction. However, the application of these results to commercial materials has to be taken cautiously due to the influence of other foreign ions in volume and alite-type.