Autolytic microsphere capsules using in cement composites: A self-healing enhancement via hydration control and secondary cracking mode alteration

Autolytic microsphere capsule (AMC) is a promising strategy for self-healing of the cement-based materials by virtue of its autolysis characteristic. In this paper, self-healing abilities of the cement composites incorporating AMCs with varying encapsule shells and core substances are studied quantitatively using a series of techniques. The AMCs with the aminotrimethylene phosphonic acid (ATMP)-3-aminopropyl triethoxysilane coupling agent bilayered shell better controls the hydration than that with the single ATMP shell. The AMCs with the high-Ca/Si core substances as healing agents has better crack closure by forming more Ca-rich healing phases, and the reloading mainly induces the tensile debonding along the interface between the self-healing products and cement matrix. The AMCs with the low-Ca/Si core substances, however, possesses higher recovery of the four-point flexural properties via generating a stronger healing phases-cement matrix interface, while the reloading generally leads to a shear fracture within the self-healing products. Such an alteration of secondary cracking mode in regenerated structures dominates the mechanical property recovery of cement composites. The maturation of AMC self-healing technology holds promise for overcoming the durability challenges faced by engineering materials in groundwater environments.