Roles of silica fume and fly ash in improving flowability, segregation stability and passing ability of self-consolidating concrete

Abstract

This paper presents the findings of a research on the effects of incorporating silica fume or fly ash on the performance of self-consolidating concrete. The flowability, segregation stability, and passing ability of the self-consolidating concrete mixtures were evaluated using slump flow test, sieve segregation test and U-box test respectively. It was found that at the same level of flowability, the superplasticizer demand increases with the content of silica fume. Compared with concrete produced with pure cement, incorporation of 5% silica fume in the concrete mixtures reduces the segregation stability and passing ability of the concrete, but the reduction is less significant when the silica fume content is increased to 10%. On the other hand, incorporation of 25% fly ash in the concrete mixture improves both the segregation stability and passing ability, but the mixtures require higher superplasticizer dosage for a given flowability. Finally, the design considerations for self-consolidating concrete are discussed.