Influence of K2HPO4 or CaSO4 center dot 2H(2)O on the hydration of alite

This study discusses the influence of K2HPO4 or CaSO4. 2H(2)O on the hydrat ion of alite, a main composition of ordinary Portland cement. The early sta ges of hydration were measured by a conduction calorimeter. The added amoun ts of K2HPO4 or CaSO4. 2H(2)O were from 0 to 3% (counted as P2O5) or from 0 to 10% (counted as SO3), respectively. The rate of heat liberation of alit e was retarded by the addition of K2HPO4 and accelerated by the addition of CaSO4. 2H(2)O. At 1.5% K2HPO4 addition, the retardation effect of K2HPO4 s howed a maximum. On CaSO4. 2H(2)O addition, as the amount of CaSO4. 2H(2)O increased, the acceleration effect of CaSO4. 2H(2)O increased. The reaction ratio of alite was measured by XRD at late stage of the hydrat ion. Calcium silicate hydrates produced by hydration of alite with 1.5% K2HPO4 o r 4% CaSO4. 2H(2)O included P2O5 or SO3, respectively. These CaO/SiO2 ratio s of calcium silicate hydrates were higher than that of alite without addit ives. Calcium silicate hydrates could contain P2O5 or SO3 with CaO, and P-2 O-5 and SO3 influenced the morphology of produced calcium silicate hydrate s.