Ternary blending of cement with fly ash microsphere and condensed silica fume to improve the performance of mortar

The addition of condensed silica fume (CSF) to fill into the voids between cement grains would release the water entrapped there to form water films for lubrication. However, the large surface area of CSF would thin down the water film thickness (WFT). By adding also a cementitious material that is finer than cement but not as fine as CSF, such as fly ash microsphere (FAM), the water entrapped in the voids could be released without excessively increasing the surface area. This may produce a larger WFT and better flowability than adding CSF alone. In this research, ternary blending of cement with FAM and CSF was studied by testing mortar mixes with different amounts of FAM and CSF added. It was found that the WFT is the key factor governing the properties of mortar and that ternary blending of cement with both FAM and CSF does offer some advantages.