The influence of C4A3S̄ content and ratio on the performance of calcium sulfoaluminate-based cements

Abstract The effect of the variation in C4A3S content (expressed as C 4 A 3 S C 5 S 2 S weight ratio ranging from 1:5 to 3:1) on the ternary system C4A3SC5S2S CS having a constant C S C 4 A 3 S ratio of 0.5, has been studied. At the fixed w s ratio of 0.4 the mechanical strength of the system at early ages (1–28 days) increased with higher C4A3S content. However, depending on the curing conditions, compositions containing more than 50% C4A3S showed expansion, cracking and loss of strength at later ages, due to the insufficient water used. Moreover compositions with more than 20% C4A3S and increasing C4A3S content gave progressively lower mechanical strength, when hydrated with the fixed water/reactants (C4A3S + CS) ratio of 0.86, i.e. 10% more than the stoichiometric water requirement. Thus, both C4A3S content and w s ratio must be optimized in order to achieve satisfactory performances at early and later ages. The best behaviour was obtained with cements containing 30–40% C4A3S hydrated with a w s ratio ranging from about 0.35 to 0.50.