THE INFLUENCE OF C(4)A(3)(S)OVER-BAR CONTENT AND W S RATIO ON THE PERFORMANCE OF CALCIUM SULFOALUMINATE-BASED CEMENTS/

The effect of the variation in C(4)A(3) (S) over bar content (expresse d as C(4)A(3) (S) over bar/C5S2 (S) over bar weight ratio ranging from 1:5 to 3:1) on the ternary system C(4)A(3) (S) over bar-C5S2S2 (S) ov er bar-C (S) over bar having a constant C (S) over bar/C(4)A(3) (S) ov er bar ratio of 0.5, has been studied. At the fixed w/s ratio of 0.4 t he mechanical strength of the system at early ages (1-28 days) increas ed with higher C(4)A(3) (S) over bar content. However, depending on th e curing conditions, compositions containing more than 50% C(4)A(3) (S ) over bar showed expansion, cracking and loss of strength at later ag es, due to the insufficient water used. Moreover compositions with mor e than 20% C(4)A(3) (S) over bar and increasing C(4)A(3) (S) over bar content gave progressively lower mechanical strength, when hydrated wi th the fixed water/reactants (C(4)A(3) (S) over bar + C (S) over bar) ratio of 0.86, i.e. 10% more than the stoichiometric water requirement . Thus, both C(4)A(3) (S) over bar content and w/s ratio must be optim ized in order to achieve satisfactory performances at early and later ages. The best behaviour was obtained with cements containing 30-40% C (4)A(3) (S) over bar hydrated with a w/s ratio ranging from about 0.35 to 0.50. Copyright (C) 1996 Elsevier Science Ltd