Crack Healing Performance Of Basalt Fibre-Reinforced Concrete With Bacillus Subtilis

Abstract

This study investigates the crack healing performance and durability enhancement of M40 grade concrete incorporating Bacillus subtilis and basalt fibres. A bacterial dosage of 1.5% by weight of cement and 0.5% chopped basalt fibres (24 mm length) by volume were used to create a hybrid self-healing concrete mix. The primary objective was to evaluate the influence of microbial-induced calcium carbonate precipitation (MICP) and fibre bridging on crack closure and mechanical recovery. Mechanical testing included compressive and flexural strength, while healing assessment involved visual crack width monitoring and ultrasonic pulse velocity (UPV) recovery. Results revealed that the hybrid mix exhibited significant reductions in initial crack width and enhanced load-bearing capacity compared to control and bacteria-only mixes. Healing efficiency reached over 90% for cracks up to 0.4 mm, while UPV recovery exceeded 100%, indicating full internal crack closure. Visual imaging confirmed progressive calcite deposition across curing periods. The combined action of bacteria and basalt fibres proved effective in controlling crack width, enhancing mechanical integrity, and promoting robust self-healing, thereby demonstrating potential for durable, sustainable, and maintenance-free concrete structures.