Triple Blending with Fly Ash Microsphere and Condensed Silica Fume to Improve Performance of Cement Paste

Abstract

In theory, the addition of fly ash microsphere (FAM), which is finer than cement, and condensed silica fume (CSF), which is even finer, to successively fill the voids between cement grains can increase the packing density of the cementitious materials and reduce the volume of voids to be filled with water. This would release more water to increase the flowability at same water/cementitious materials (W/CM) ratio or allow the W/CM ratio to be lowered to increase the strength at same flowability requirement. This study was aimed to evaluate the effects of FAM and CSF on the packing density of cementitious materials and the water film thickness (WFT) in cement paste and investigate the effects of the WFT on the flowability, cohesiveness, adhesiveness, and strength of cement paste. The results showed that adding FAM and CSF can significantly increase the packing density and WFT and thereby greatly improve the overall performance of cement paste.