بررسی بتن خود ترمیم شونده با استفاده از باکتری باسیلیوس سوبتیلیس

Abstract
Spontaneous healing involves the formation of self-healing compounds through the continuous hydration of unhydrated cementitious materials, which have limited ability to heal cracks. On the other hand, autohealing uses external agents such as superabsorbent polymers, biological agents, high pozzolanic materials, and chemical agents to seal cracks.In this study, the use of Bacillus subtilis bacteria was investigated to improve compressive strength and crack repair. Some researchers added Bacillus subtilis bacteria directly to concrete. The results of these studies showed that adding Bacillus subtilis bacteria directly significantly improves the compressive strength of bacterial concrete compared to control concrete. Bacillus subtilis bacteria also produce calcium deposits and fill cracks in concrete. However, some researchers investigated the indirect (encapsulated) addition of Bacillus subtilis bacteria with different carriers in concrete. The results showed that using a phenyl vinyl alcohol (PVA) carrier containing Bacillus subtilis bacteria in concrete increased the compressive strength of the samples compared to other samples containing bacterial carriers. Also, the concrete mixture containing Bacillus subtilis bacteria with 30% fly ash carrier showed higher healing compared to other mixtures. Overall, the results of this study showed that the use of bacteria with Bacillus subtilis plays a significant role in improving the compressive strength and self-healing capacity of concrete, which can significantly improve the durability of concrete structures.The results obtained on concrete samples containing Bacillus subtilis bacteria compared to control concrete, bacterial concrete had a maximum compressive strength of 18.20 MPa (3.59% increase), 54.29 MPa (15.61% increase), and 88.32 MPa (19.55% increase) after 14, 7, and 28 days, respectively. After 28 days of curing, the self-healing index showed that bacterial concrete had a higher normalized self-healing index of 1.12 compared to control concrete. The results of the research on bacterial concrete containing Bacillus subtilis bacteria showed higher compressive strength compared to normal concrete in all grades of concrete. Also, the compressive strength of concrete containing Bacillus subtilis bacteria with a bacterial concentration of 5^10 cells per ml with concrete grade M30 on day 28 was slightly higher than other samples. In this study, sediment was observed on the surface of concrete samples Cracked bacteria and filling of smooth cracks showed the effectiveness of crack repair.The compressive strength results obtained on concrete samples containing Bacillus subtilis bacteria with carriers of phenyl vinyl alcohol fibers, sisal fibers and expanded perlite and concrete samples containing phenyl vinyl alcohol fibers, sisal fibers that do not contain Bacillus bacteria and normal concrete. The self-healing concrete of Bacillus subtilis with polyvinyl alcohol (PVA) fibers added is stronger than the two carriers with bacteria and without bacteria and normal concrete. The reason is that polyvinyl alcohol (PVA) fibers have a binding role in concrete compared to the expanded perlite material.The repair effect in concrete with Bacillus subtilis bacterial solution added at a concentration of 2.5 oz with carrier is higher compared to the other two groups of self-healing concrete.For both normal concrete and self-healing concrete containing Bacillus subtilis bacteria, 100% natural aggregate provides the maximum strength Slow and in case of strength recovery after repair, concrete mix containing 30% fly ash aggregate showed good results. In this test, mix B2 with 30% fly ash aggregate showed high repair performance compared to other mixes. Review History