COMPUTATION OF X-RAY POWDER DIFFRACTOGRAMS
Keywords:Portland cement, X-ray diffraction, crystal structure, characterization, Rietveld method
The importance of computed X-ray diffraction patterns of various polymorphs of alite (M3, T1, R), belite (β, γ ), aluminate (cubic, orthorhombic), aluminoferrite, gypsum and hemihydrate in the quantitative phase analysis of cement and its early stage hydration performance is highlighted in this work with three OPC samples. The analysis shows that the predominant silicate phases present in all the samples are M3 -alite phase and β-belite phase, respectively. Both cubic and orthorhombic phases of C3 A, brownmillerite, gypsum and hemihydrates are present at different levels. Quantitative phase analysis of cement by Rietveld refinement method provides more accurate and comprehensive data of the phase composition compared to Bogue method. The comparative hydration performance of these samples was studied with w/c ratio, 0·5 and the results are interpreted in the light of difference in phase compositions viz. β-C2 S/C3 S ratio, fraction of finer cement particles present in the samples and theoretical modeling of C3 S hydration.