The effect of air-entraining admixture and superabsorbent polymer on bond behaviour of steel rebar in pre-cracked and self-healed concrete

Abstract

This paper intends to study the effect of air-entraining admixture (AE) on self-healing method at rebar-concrete interface using superabsorbent polymer (SAP). AE with a constant dosage of 0.83 kg/m3, and 0.25% and 1.0% SAP dosages are considered. Two types of superabsorbent polymer with different chemical compositions and particle sizes are considered for the experimental tests. Pull-out test results of mixtures containing AE admixture are compared with those in non-AE concrete. Scanning electron microscopy/energy dispersive X‐ray spectrometry (SEM/EDS) along with microscopic analysis is performed to study the healing products at crack surface and SAP macro voids around the rebar. Overall, results indicate that AE admixture has a considerable impact on the performance of the self-healing method at the rebar-concrete interface especially for higher dosage of SAP (1.0%). This can be attributed to the internal voids networks around the rebar generated by AE admixture, which can ease the water transfer between SAP macro voids to participate in healing cracks after wet-dry cycles. SEM analysis shows that stalactites, healing products at the external surface of crack, are composed of a large amount of calcium and oxygen.