Effects of CSF on strength, rheology and cohesiveness of cement paste

A number of cement paste samples with condensed silica fume (CSF) contents ranging from 0% to 25% and different water contents were made and their respective strength, rheological properties, cohesiveness and packing density were measured. The results showed that whilst the addition of CSF would increase the strength of cement paste, there is an optimum CSF content beyond which further addition of CSF would cause reduction in strength. More importantly, the addition of CSF has great effects on the flowability, cohesiveness and packing density of cement paste, and under certain conditions can increase both the flowability and cohesiveness. In-depth analysis revealed that the various rheological properties are governed mainly by the water film thickness whereas the cohesiveness is dependent not just on the water film thickness but also on other factors.