Quantitative analysis of phase transition of heated Portland cement paste

This paper studies Portland cement paste heated up to different temperatures ranging from 105 to 1,000 °C by X-ray diffraction. The heated cement paste samples are kept isothermal in furnace for 6 h and cooled down to 100 °C. Then the samples are picked out and grinded into fine powders. 10 % Corundum is blended with cement paste powders as an internal standard. Quantitative phase analysis of cement paste samples is performed by Rietveld method. With the addition of a crystalline standard, the mass fractions of all crystalline phases as well as amorphous calcium silicate hydrate (C–S–H) are determined. The Rietveld analysis results are compared with independent measurements of the same material by thermal analysis (TG/DSC). The phase transition of Portland cement paste is discussed. An empirical relationship between the dehydration degree of C–S–H and the crystallization degree of C–S–H is derived.