Abstract
Growing amount of agricultural waste and its burning in open environments is contributing towards the carbon emissions and triggering serious health hazards. It can be reduced by beneficially employing the wastes, as carrier media of calcite (CaCO3) precipitating microbes, into the concrete. Instant formation of CaCO3 in micro-cracks using bio-inspired concrete prevents aggressive ions to penetrate into the inside concrete, hence boosting the durability. In the present study, Bacillus subtilis (BS) were immobilized with nano-micro sized carbonaceous solid material, bagasse ground biochar (GBC), to enhance the CaCO3 precipitation. The mechanical behavior of the samples was investigated in terms of bending and compression. Biochar immobilized BS concrete (BSCM) exhibited promising flexural behavior, higher strain energy storing capability, and higher modulus of fracture toughness. Moreover, 23.18% enhancement in compressive strength was achieved after 56 days of curing in comparison to the control samples. Furthermore, autonomous cracks closure mechanism was monitored as the function of time, the BSCM showed effective crack healing with maximum 100% and 68% sealing of 500 μm and 800 μm wider cracks respectively, in the selected time frame. The BSCM samples revealed higher ultrasonic pulse velocities and lesser sorptivity due to the densified microstructure of concrete by bacterial precipitated CaCO3. The x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy and thermal gravimetric analysis confirmed the existence of CaCO3 inside the cracks. Consequently, immobilizing BS with bagasse GBC could be considered as a promising solution for prompt cracks repairing and enhancing the mechanical properties of concrete.
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