Crystallographic Analysis of Sr-Bearing Ye'elimite

Ye'elimite (C(4)A(3)$) is the main phase in calcium sulfoaluminate (CSA) cement. To improve the performance of CSA cement, substitutions of Ca2+ by Sr2+ cations in C(4)A(3)$ can be done to synthesize Sr-bearing ye'elimite. In this study we performed crystallographic analysis of Sr-bearing ye'elimite (C(4-xx)A(3)$) synthesized with 0.25-3.00 mol Sr2+ ions. The effect of strontic substitutions on the crystal structure of ye'elimite was investigated. Compositions of clinkers and the lattice parameters of Sr-bearing ye'elimite were determined by the Rietveld method. Results showed that strontic substitutions promoted the transformation of the crystal system from orthorhombic to cubic for ye'elimite. Sr-bearing ye'elimite almost purely exists in a cubic structure when amounts of strontic substitutions exceed 1.25 mol. The amount of Sr-bearing ye'elimite in crystalline phases is over 95 wt% while impurities in the clinkers of Sr-bearing ye'elimite contain minor amounts of calcium aluminate phases. Lattice parameters of Sr-bearing ye'elimite exhibit linear growth with strontic substitutions increasing for both cubic and orthorhombic systems. Both calcium and strontium evenly distribute in the particles of Sr-bearing ye'elimite.