Title: Repair of Alkali-Silica Reaction-Induced Cracks Using Bacteria: Crack Recovery and Other Properties
Author(s): Yao Luan, Takumi Arasawa, Hiroshi Mutsuyoshi, and Rikako Kawana
Publication: Materials Journal
Appears on pages(s): 133-142
Keywords: alkali-silica reaction (ASR); Bacillus pasteurii; calcium carbonate; crack repair; expansion; gas permeability; pore structure; water absorption; yeast fungus
Cracks in concrete structures increase the penetration of water and deleterious ions, leading to accelerated deterioration. An innovative repair method using bacteria is currently gaining attention. In this method, CO2 is released by bacteria and reacts with calcium ions (Ca2+) to form CaCO3, which heals cracks by deposition. In this study, alkali-silica reaction (ASR)-induced cracks were repaired using two types of bacterial material, containing yeast and Bacillus, respectively. Microbial grouts containing these bacteria were prepared and used to impregnate mortar surfaces with ASR-induced cracks. The cracks were observed to be healed over time, and water absorption and gas permeability were reduced after repair. Thermogravimetric analysis (TGA) revealed that the main precipitate was CaCO3, while mercury intrusion porosimetry (MIP) indicated that the CaCO3 also densified the surface layer of the mortar by refining the pore structure. After repair, the specimens were immersed in water and NaOH solutions to test whether re-expansion occurred. The results showed that when immersed in 0.1 mol/L NaOH or water, the repaired specimens exhibited less expansion than the unrepaired ones.