The effect of microorganisms on the improvement of some physical and mechanical properties of cement mortars

In this thesis, the effects of bacterial use on the mechanical and physical properties of mortar samples prepared by using pumice and recycling aggregates and on self healing of cracks in samples were investigated. Bacillus subtilis bacteria were grown in Tryptic Soy Broth (TSB) medium and the grown bacteria were planted in 4 different media with TSB, Modifiye Luria-Bertani (MLB), urea-calcium phosphate and urea-calcium chloride content and then encapsulated into the recycling aggregates and pumice aggregates. Bacterial aggregates were replaced with limestone aggregates in volume ratios of 10%, 20%, 30%, 70% and 100%. Water, aggregate and cement were designed based on 100% limestone mixture in proportions of 1, 3, and 0.5, respectively. As mechanical properties, 3, 7, 28 days compressive strength, 28 days bending strength and UPV measurements were made, as physical properties, 28 days water absorption, sorptivity and total porosity rates were examined. It has been observed that the physical and mechanical properties of the samples prepared with recyling aggregate and pumice content of 30% and below are significantly enhanced. Porosity ratio and sorptivity ratio decreased and the cracks forming up to 0.3 mm in the samples were observed to be healed in 28 days. Compared to the control mixture, compressive strengths mostly have increased in mixtures recyling and pumice content at 70% and below, containing bacterial MLB, urea-calcium phosphate and urea-calcium chloride media. Encapsulated bacterial urea-calcium chloride media in 10% pumice content mixture showed the best result with an increase of 24% in compressive strength. Keywords: Bacteria, self healing, crack healing, mechanical properties, physical properties, calcium carbonate deposition