The influence of air entraining agent on bond strength and mortar microstructure

Air entraining agents are widely used in Australia to impart plasticity to the fresh mortar. the entrainment of a large quantity of air into the mortar affects the hardened mortar properties, in particular the mortar-to-unit bond strength. This report is a summary of the investigations carried out at the University of Newcastle to evaluate the effects of air entraining agents on bond strength and mortar microstructure. The microscopy work indicates that the reduction in bond strength is due to the reduced transport of cementitious material to the brick/mortar interface and through the formation of 'pseudo' aggregate particles within the cement paste by the entrained air bubbles. These effects are discussed in this report.