Rapid and highly effective self-repair of concrete cracks based on magnetic microbes

In self-repair technology for concrete cracks based on microbial-induced calcite precipitation, microorganisms are usually dispersed throughout the matrix, resulting in low utilisation and weakening the repair effect. In this work, Bacillus pasteurii was magnetised and was thus attracted to the cracks, improving the repair speed. The results showed that the repairability of the magnetic microbe group was significantly better than that of the pure microbe group. For 0.2–0.4 mm wide cracks (cracked at 3 days), the magnetic group achieved a 97.8% area repair rate (ARR) within 3 days, which was ten times higher than the pure group. For wider cracks (0.4–0.8 mm), the repair speed increased by 5–14 times. Additionally, increasing the dosage of the repair agent improved outcomes for cracks aged 7–28 days. With a 60% dosage, ARR of 87.9%, 88.6% and 100% were achieved for cracks less <0.8 mm cracked at 7 days, <0.6 mm cracked at 14 days and <0.4 mm cracked at 28 days, respectively.