Strength and Durability Assessment of Self-Healing Bio-Based Composite Concrete under Different Exposure Conditions

Cracks in concrete are predestined, and they lay a pathway for water and aggressive chemical substances, which leads to deterioration of concrete ingredients and affects the service life of concrete structures. In the recent years, natural fibers and bacteria species are used to improve rheological properties and to heal concrete cracks. Precipitation of calcium carbonate crystals produced by bacteria in concrete cracks is highly acceptable to increase the mechanical and durability properties. In this research, Bacillus paramycoides species is isolated from concrete efflorescence and is used for self-healing. For bacteria immobilization, natural fibers like coir, flax, and jute are used as suitable carriers. Furthermore, the study on the performance of bacteria in crack healing and strengthening properties is in need for different curing/exposure conditions such as full-wet, wet–dry, saturated normal soil, and saturated marine soil. The performance of bacteria in concrete is estimated by a series of tests such as compressive strength, compressive strength regains, tensile strength, impact strength, sorptivity, and deterioration of concrete under acid curing. Based on the test results, the selected bacteria have the ability to heal crack widths of 0.3–1.1 mm with the average healing rate of 83 %, 92 %, 76 %, and 42.5 % for full-wet, wet–dry, normal soil, and marine soil exposure, respectively. Microstructure studies were investigated for fiber-reinforced concrete and bacteria-immobilized fiber-reinforced concrete to determine the composition of elements formed in calcium carbonate precipitates. In this work, the results suggest that natural fibers can be used as sustainable carrier material for crack healing, strength, and durability improvement in concrete.