Enhancement in self-compactability and stability in volume of entrained air in self-compacting concrete with high volume fly ash

Abstract

An experimental study on the effect of entrained air bubbles on the enhancement of self-compactability in fresh concrete with high volume fly ash was investigated. The stability in terms of volume of entrained air bubbles was also analysed. In this paper, lower water retention and ball-bearing effect of fly ash and entrained air bubbles were considered to affect the self-compactability of fresh concrete. The results showed that higher fine aggregate content in mortar (s/m) of SCC can be employed as replacement ratio of cement with fly ash (fa/p) increases owing to the higher ball-bearing effect of fly ash, in spite of reduction in water to powder ratio (w/p). The ball-bearing effect of entrained air bubbles, with certain type of air-entraining agent (AEA), was also found to further enhance the self-compactability of fresh concrete with fly ash. However, the stability in volume of entrained air bubbles tended to be reduced as fa/p increased, due to higher amount of large entrained air bubbles produced. Apparently, the spherical shape of fly ash tended to cause the unification and escape of entrained air bubbles in SCC.