Abstract:
This study examines the effects of the usage of bacteria as a self-healing agent on the geopolymer paste (GP) sample's characteristics. Examining the microbial self-healing capacity of geopolymer binders, which have many advantages over traditional Portland cement, is seen as an important and necessary step because of frequently studying innovative approaches on geopolymer samples. To carry out this investigation, GP samples produced using ground blast furnace slag (GBFS) were activated only with Na2SiO3. Bacillus subtilis was selected as the healing agent for the production of GP samples. As a result of the preliminary tests in which different variables (curing environment, sample content) were examined, it was decided what the sample content to be used in the main test processes. The bacterial suspensions were prepared at ratios of 107 and 109 CFU/mL. Bacterial samples prepared at two different cell densities were added to the mixture at 1, 2 and 3% by weight of the binder. The GP samples that cured under laboratory conditions until the end of the 7th day, were subjected to healing process in three different curing environments (water, air and precipitation medium consisting of urea, yeast extract and Ca(NO3)2·4H2O After the healing process was completed, the compressive strength, rheological behaviour, geopolymerization kinetics, physical properties, microstructural and visual examinations were performed. Experimental findings demonstrated that the self-healing mechanism resulting from the metabolic activity of Bacillus subtilis can be successfully applied in geopolymer composites in terms of high durability and mechanical properties. © 2022 Elsevier Ltd