An investigation on self-healing ability of cement based composites

The service life of constructions can be increased by many passive self-healing methods with lower costs and fewer problems. Encapsulation of self-healing agents by microencapsulation technology, restriction of the crack width with fibers, and ensuring the presence of unreacted cementitious materials in matrix were the self-healing techniques investigated within the scope of this study. Enhancing and characterization of self-healing ability of cementitious composites is the main aim of this research. The self-healing mechanisms of macro/micro cracks formed under tension and compression loads were investigated by various mechanical, permeability, and microstructure analysis. Ultra high performance concrete (UHPC) was used as the cement based composite. Different mix designs have been considered to increase the amount of unreacted cementitious materials in the matrix. In addition, the self-healing capacities of supplementary cementitious materials (SCM) were evaluated through a novel test method, which has been developed to assess the bonding capacity of self-healing products in cementitious composites. The microencapsulation of sodium silicate as a self-healing agent with polymeric shell materials was one of the main objectives of this study. The synthesized microcapsules were optimized and characterized by various methods and analyses. This study has also dealt with the idea of possible microencapsulation of isophorone diisocyanate as a self-healing agent with silica-based shell for the first time in the literature. In spite of the positive effect of SCMs on self-healing ability of UHPC, it was observed that the self-healing ratios depend on critical parameters such as damage type/level and the methods used to verify the phenomenon of self-healing. The sodium silicate, which has many advantages as a self-healing agent in cementitious materials, can be encapsulated via the interfacial polymerization of shell-forming monomer on the aqueous sodium silicate droplets. In addition, promising results were obtained in the process of microencapsulation of isophorone diisocyanate in silica-based microcapsules.