A novel method of self-healing cement paste by using gel microparticles encapsulating phosphate

Abstract Concrete is liable to form cracks owing to the limited tensile strength, which prompts researchers to propose a concept of self-healing. Inspired by the biological bones self-healing, this paper utilized hydroxyapatite as healing substances of cement-based materials and designed polyacrylamide (PAM) gel microparticles as carriers of phosphate for cement paste self-healing system. Morphology and properties of PAM gel microparticles, feasibility of hydroxyapatite as healing agents and healing efficiency were studied. The results showed that the three-dimensional crosslinked structure of PAM can encapsulate phosphate and the content of crosslinking agent can control the release rate and cumulative release of phosphate. Chloride permeability of cement paste containing PAM with phosphate is reduced after self-healing compared with plain cement paste. The healing efficiency of self-healing cement-based materials can reach 81.9% for compressive strength repair ratio and 93.2% for resistance to water penetration repair ratio after curing for 28 days. The white reaction products at the repairing section are proved to be hydroxyapatite according to multiple analytical techniques.