The Effect of Bacillus Subtilis on Self-healing of Zeolite Concretes

Today, the use of self-healing concretes has attracted the attention of various researchers. In this paper, the effect of Bacillus subtilis bacteria with different concentrations were used for evaluation on concrete containing zeolite.The mentioned bacteria were produced in the laboratory and added to the concrete mixing plan. In order to evaluate the effect of Bacillus subtilis bacteria on specimen with zeolite, resistance and durability tests including compressive strength, ultrasonic, water penetration test and water absorption tests were performed on the specimen at different ages. Also, using scanning electron microscope (SEM) and optical microscope, the self-healing of concrete was evaluated. The results of the compressive strength test showed that the specimen containing zeolite with a concentration of 2.8×108 cells/ml increased the compressive strength by 16.76% and the specimen without zeolite increased the compressive strength by 13.51%. Also, the presence of Bacillus subtilis bacteria in the mixing design led to a 15% decrease in water absorption of specimens without zeolite and 30% of specimens with zeolite. Based on the results of the experiments, the most suitable concentration, for the simultaneous improvement of the resistance parameters and durability among the different concentrations of Bacillus subtilis bacteria, is suggested to be 2.8 x 108.