Self-healing in cementitious system using interface enhanced capsules prepared at room temperature

Abstract

Encapsulation has been extensively applied in the self-healing of cementitious materials due to the diversity of encapsulating materials. Nonetheless, the weak interfacial bonding of polymer capsules and cementitious materials commonly reduces the healing efficiency, the preparation of which is complicated and not environmentally friendly. In this paper, a nano-silica reinforced calcium alginate/epoxy resin capsule (S1) was prepared using a simple and green chelating method at room temperature. The strong bonding of the shell containing nano-silica with cementitious materials makes it easier for capsules to be triggered to achieve higher self-healing efficiency. Their effects on cementitious materials were measured to determine the reinforcing mechanisms, microstructure and mechanical properties of capsules. The experimental results demonstrated that S1 possessed higher thermal stability (310.0 °C), higher mechanical strength and lower water absorption (46.95% in cement filtrate) than samples without nano-silica (S0). The compressive strength of S1 cementitious material increased by 18.9% compared with S0 cementitious material because of the decrease in porosity and the increased mechanical properties of the S1 capsule. Moreover, the self-healing efficiency of S1 cementitious material improved greatly by 112.7%, which was related to the more efficient rupture of S1. The nano-silica in the capsule increased the surface roughness of S1 and reacted with cement matrix via a pozzolanic reaction, thereby achieving efficient self-healing of cementitious system through a stronger interface.