DOI:
AUTHOR(S)
Akter F., Dr. Islam M S, Apu M H, Likuzzaman M, Sarker M M, Mazumder M M
ABSTRACT
Bacterial or self-healing concrete employs specific bacterial strains to improve various performance characteristics, including mechanical strength, durability, and overall service behavior. These bacteria are spore-forming gram-positive microorganisms capable of consuming calcium lactate available in the concrete matrix. These microorganisms are capable of producing calcium carbonate (calcite), which naturally seals cracks and voids over time, thereby enhancing the concrete’s mechanical properties. The present study focuses on how varying amounts of Bacillus subtilis affect the development of compressive strength in microbial concrete. For this purpose, a total of 36 cylindrical concrete specimens (100 mm × 200 mm) were prepared using a cement: sand: coarse aggregate ratio of 1:1.5:3 and a constant water-cement ratio of 0.45. The bacterial solution was prepared at a concentration of approximately 107 CFU/mL and added to the mix in quantities of 30 mL, 45 mL, and 60 mL per liter of mixing water. Compressive strength tests were carried out after 7, 14, and 28 days of curing. Additionally, load-displacement behavior and failure modes were analyzed. The findings confirmed that adding bacteria considerably enhanced the 28-day compressive strength of the concrete. Compared to the control concrete mix without bacteria, the strength increased by 47%, 63%, and 48% for specimens containing 30 mL, 45 mL, and 60 mL per liter of mixing water, respectively. In addition, the incorporation of bacteria improved the modulus of elasticity of the concrete. Among the three concentrations, 45 mL per liter of mixing water was found to be the optimal dosage for maximizing strength development.
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