Investigation of properties of bacterial containing geopolymer mortars

In recent years, a new material form with cement properties called geopolymer has been developed. Geopolymer mortars are new generation inorganic binders with a high potential to replace Portland cement mortars, but geopolymer is more brittle than concrete. Therefore, it is highly desirable to impart self-healing to the geopolymer. Microfibers are used to control crack width in concrete, while broad chemicals are added to concrete to reduce crack width. However, most strategies such as epoxy systems, acrylic resins and silicone-based polymers involve the use of expensive and often environmentally harmful materials. In another approach, bacteria that can withstand the alkaline environment in concrete are used to induce microbial carbonate precipitation to seal and heal cracks. The microbial carbonate precipitation method is a potential way to enable self-healing in geopolymer. In this study, self-healing geopolymer mortar properties were investigated using bacteria. Since the use of bacteria in geopolymer mortar was almost never investigated before, cement-containing studies were investigated, and it was determined that Bacillus type bacteria were used. In the experimental study, geopolymer mortar samples were produced using Bacillus Subtilis. Bacillus Subtilis spores were added directly to the geopolymer mortar without encapsulation or immobilization. The physical and mechanical properties of the samples were investigated and SEM analyses were performed on the mortar samples. Experimental results show that the use of bacteria has a positive effect on both physical and mechanical properties. Calcite formation was observed in SEM images and showed that it prevented crack formation.