Investigation of healing performance on pre-damaged mortar specimens using MICP bacterial vegetative cell

Abstract

This study aims to investigate the healing performance of cracked mortars using bacterial vegetative cell. Cylindrical samples of mortar with diameter of 100 mm and depth of 50 mm were prepared. Cracks were induced by a compression machine with crack widths of ≤175 µm and 175-350 µm. Crack healing procedures were conducted by dropping the Bacillus sphaericus bacterial vegetative cell and nutrient to the crack. Bacteria-to-nutrient ratios of 20:500 µL and 40:1000 µL were applied each day. Cracked specimens were repaired for 7 cycles under the wet-dry cycle condition. Then, the healing ratio was determined by measuring
crack width using microscope. The results show that healing ratios of crack width of ≤175 µm healed by bacteria-to-nutrient ratios of 20:500 µL and 40:1000 µL were 90.1% and 97.0%, respectively. On the other hand, healing ratio of crack width of 175-350 µm was 54.0% . Moreover, the results of healing ratios in every repairing cycle indicate that the cracks in all specimens were continuously repaired until 7 cycles and exhibited a tendency of further remediation.