2003 Volume 52 Issue 3 Pages 294-300
We discussed the influence of additives, ground granulated blast-furnace slag and limestone powder, on the fluidity of cement paste with polycarboxylate-based superplasticizers (PC) by considering solid volume of powder in packed state, early hydration of paste, adsorption characteristics of PC and steric hindrance effects. The fluidity of cement paste increased with increasing the addition of additive. The solid volume of powder in packed state and the amount of adsorbed PC did not correlate with the fluidity. The loss on ignition decreased with the addition of additive. It is suggested that the decrease of combined water relates to the increase of fluidity. The fluidity increased linearly with decreasing sulfate ion concentration by the addition of additive. We had showed that sulfate ion reduced the thickness of adsorbed PC and steric hindrance effects. The results of present study suggest that the change in fluidity due to the addition of additive is caused by the change in the dispersion of particles by sulfate ions.