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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. [ABSTRACT FROM AUTHOR]

This paper presents a bio-inspired autolytic mineral self-healing method for cementitious materials. The autolytic mineral microsphere (AMM) consists of porous silica microsphere adsorbed with sodium silicate as healing agent and polyvinyl pyrrolidone (PVP) as resoluble coating material which will be autolyzed gradually under alkaline solution. The porous silica microsphere and coating film were prepared by sol-gel method and solvent evaporation respectively. The microstructure of AMM were characterized by environmental scanning electron microscopy (ESEM) and specific surface & pore size analysis instrument. The PVP thickness was measured by transmission electron microscope (TEM). Autolytic behavior of AMM was studied using Ultraviolet–visible (UV-VIS) spectrophotometer under different pH values, temperature and PVP thickness. Experimental results show that autolytic behavior is mainly controlled by PVP thickness, and the dissolution rate of sodium silicate is affected by pH values and temperature. Compressive strength recovery of cementitious materials is greatly enhanced by adding AMM. [ABSTRACT FROM AUTHOR]