Influence of chemical admixtures on performance of biomineralized self-healing cement-based materials

Factors affecting the durability of concrete structures are generally associated with each other. Due to its brittle nature, concrete can crack when stress is applied. Recent research in the field proposes that it might be possible to develop a smart, cement-based material that can self-heal itself. Self-healing is the ability of concrete to heal the cracks without any external application. Self-healing property of concrete can be obtained via different approaches. Use of biomineralization is a novel technique to provide self-healing in cement-based materials. Biomineralization is a biochemical process in which microorganisms stimulate the formation of minerals. In this system, calcium carbonate (CaCO3) is induced by leveraging the metabolic activity of microorganism and self-healing is obtained by sealing of the cracks with CaCO3.The goal of this study to investigate the influence of bacterial self-healing agent on performance of cement-based materials. In this study, the bacteria will be introduced to cement paste with its growth media without any additional manipulation such as encapsulation. Performance of cement-based mortar was evaluated by Vicat needle test, compressive strength test, thermogravimetric analysis and crack healing ability. While incorporation of bacterial cells did not affect the compressive strength and chemical composition, there was a significant delay in initial setting time. This was attributed to the nutrient medium added along with bacterial cells. With this approach, the flexural cracks on the mortar surface were sealed with the CaCO3. At last but not the least the influence of superplasticizers and air entraining agents (AEA) on self-healing was investigated. While the superplasticizers improved the self-healing efficiency of the bacterial cells, AEA relatively educed the amount of CaCO3precipitation within the cracks