Enhanced entrainment of fine air bubbles in self-compacting concrete with high volume of fly ash using defoaming agent for improved entrained air stability and higher aggregate content

This paper presents an experimental study on the use of a defoaming agent (DA) to promote entrainment of fine air bubbles for improved volumetric stability of entrained air in self-compacting concrete (SCC) with fly ash. The possibility of increasing the aggregate content of self-compacting concrete with fly ash through the ball-bearing effect of fine entrained air bubbles is also investigated. Lower water retention and the ball-bearing effect of both fly ash and entrained air bubbles are considered to affect the self-compactability of fresh concrete. The results suggest that, generally, the employment of DA improves the stability of entrained air bubbles owing to the reduced entrainment of large air bubbles. The self-compactability of fresh concrete with fly ash is found to improve as dosage of DA increases, due to the ball-bearing effect of fine entrained air bubbles. Evidently, a higher aggregate content is also made possible through use of a certain type of air-entraining agent (AEA), due to the lower amount of large entrained air bubbles.