Effects of fly ash, mixing procedure and type of air-entraining agent on coalescence of entrained air bubbles in mortar of self-compacting concrete at fresh state

The air size distribution of the air-entrained SCC mortar in the fresh state is determined by an Air Void Analyser (AVA). Changes in the air size distribution over a 120 min period are analysed to evaluate bubble coalescence. The results suggest that the use of fly ash in the SCC can result in a higher degree of coalescence of the fine air bubbles. The various types of AEA resulted in air bubbles with different degrees of coalescence. Further, adding the AEA to the mix after the superplasticiser (SP) inhibits the coalescence of air bubbles. Evidently, the degree of coalescence of air bubbles can be reduced by careful selection of the AEA and the mixing procedure.