Microencapsulation and evaluation of styrene maleic anhydride/epoxy for mechanical triggering self-healing of cementitious materials

Abstract

Capsule-based self-healing of cementitious materials is a promising solution to improve the serviceability and to prolong the longevity of concrete structures. The successful use of mechanical triggering microcapsules to achieve cracks healing is still challenging and is closely dependent on the breakage of capsules upon crack formation.In this study, self-healing microcapsules were synthesized via complex coacervation using a styrene maleic anhydride (SMA) shell and an epoxy resin adhesive. The SMA/gelatin bi-layer wall formed with gelatin as the out layer for better trigger sensitivity under crack formation. The effects of various preparation parameters, referring to stirring rate, temperature, core-shell ratio and pH, have been investigated by characterizing the microcapsule morphology, shell thickness, size distribution, and chemical nature. The morphology demonstrates the encapsulation ability of SMA/gelatin and the spherical shape facilitates the rupture under crack formation. The elastic modulus and hardness of the microcapsules were determined using nano-indentation to assess the interfacial bonding and likelihood of mechanical triggering. Self-healing functionality of the developed microcapsules were validated in paste according to the in situ Acoustic Emission measurement.