Effect of direct addition of two different bacteria in concrete as self-healing agent

In this paper, a suitable and practical method to make bacterial concrete on a large and bulky scale is presented. In this method, first, bacteria compatible with concrete are extracted and identified. The bacteria are then added to the concrete in solution in a simple way. To find bacteria compatible with concrete, first, the soil near the roots of plants (rhizosphere) and two types of cement called Portland pozzolanic cement (PPC) for Darab city and Portland cement type 2 (PC2) for Hormozgan-Bandar Khamir were used. After extracting the cultured samples, it was observed that bacteria grew only in the soil sample and did not grow significantly in the cement samples. Therefore, the cultivation and reproduction of bacteria from concrete fragments were investigated. At this stage, concrete samples were prepared with two types of cement (PPC and PC2). Then, some concrete powder containing all the constituent materials was used to extract bacteria. The resulting bacteria were identified by the Deoxyribonucleic Acid (DNA) testing. Bacterial samples obtained from the concrete made of PPC with certainty exhibited the genus and species of Bacillus paralicheneniformis, but in the case of bacterial samples of concrete prepared with PC2 can only be bacterial Cited by Bacillus sp. Afterward, 4 mixing designs were designed to make concrete from the two abovementioned types of cement, with the addition of bacteria and without the addition of bacteria. In this mixing design, bacterial sediments were added to the solution and directly to the concrete mixing design. Finally, the compressive strength, water absorption and crack recovery in concrete samples were investigated. The results indicated that the presence of bacteria had slight effect on the compressive strength of concrete. The water absorption percentages of bacterial concrete samples with PPC and PC2 were 0.07 and 0.19% higher than those of non-bacterial samples, respectively. Both types of bacteria had the ability to repair cracks. Uncontrolled cracks in concrete samples were repaired to a width of at least 39.82 mu m.