Effect of microbiological calcification on properties of concrete mixture

In this study, microbial induction calcium carbonate production (MICP) method was used and Bacillus megaterium was used as biological additives. The bacterium was used at a density of 30 × 105 cells/ml was added directly to the concrete mixing water. 10 ×10 ×10 cm dimensions of cube concrete samples were produced. The effect of CaCO3 formation on the properties of concrete was investigated by using microbial enzymes of bacteria. In order to determine the effect of bacterium on concrete properties, compressive strength, water absorption rate, capillary water absorption rate, fire effect and acid effect test results was compared with that of control samples. In addition to the effect on the mechanical properties of the contaminated concrete, the effect of filling the concrete cracks and pores on the surface was observed. Calcium carbonate formation was ensured by keeping the bacteria added samples which were pre-cracked in the compressive strength press in the same amount of liquid containing bacteria and medium. In compressşive strenght test; water cured control sample, bacterial and nutrient containing liquid cured control sample, and bacterial and nutrient cures bacterial concrete were used in 3 types. 7-day and 28-day compressive strength results that the highest compressive strength value was obtained in bacterial concrete. Compared to the control sample, it increased 5.07 % in 7 days and 9.54% in 28 days. The CaCO3 produced by the bacteria also reduced the water absorption values. Water absorption rate of 28 days by weight 12.99 %, and 11.72 % by volume reduction in water absorption. The additive, which also had a positive effect in the capillary water absorption test, reduced capillity to close to 50%. In the fire effect test, as a result of calcitization, which increases the resistance against heat, bacterial concretes were affected by 13.78 % less concrete compared to the control samples. Bacteria which showed positive effect in durability test showed more resistance to HCL acid. It was found that the compressive strength results of the bacteria exposed to acid effect were 40.12% higher than the control samples. Using properties of healing the crack by CaCO3, 0.3 mm crack on specimens surface was healed thanks to bacterium. Calcium carbonate formation was clearly observed on surface of concrete specimens.