Mitigation of alkali-silica reaction by microbially induced CaCO3 protective layer on aggregates

• Published in: Construction & building materials 2022-04, Vol.328, p.127065, Article 127065
• Main Authors: Lu, Chun-Hua, Bu, Sen-zhuang, Shahin, Mohamed A., Zheng, Yu-long, Cheng, Liang
• Format: Article
• Language: English
• Subjects: Alkali-silica reaction; Concrete expansion; Inhibition; Microbially induced carbonate precipitation
• ISSN: 0950-0618
• DOI: 10.1016/j.conbuildmat.2022.127065

[Display omitted] •MICP induced CaCO3 layer was coated onto the aggregates surface by submerging method.•Alkali-silica reaction of active aggregates was mitigated by the CaCO3 protective layer.•The mortar bar specimens using the pre-treated Alkali active aggregates were prepared.•Surface cracks of the mortar bar specimens were completely inhibited.•The pretreatment resulted 50% reduction in expansion and 35% increase in UCS. The water-swelling gel produced by the alkali-silica reaction (ASR) usually causes the expansion and cracking of the concrete, leading to a reduction in mechanical property. It is found that the ASR can be inhibited to a certain degree by the environmental-friendly microbially induced carbonate precipitation (MICP) technology, which can form a protective layer of CaCO3 crystals on the active aggregates surface, after the treatment by mixing ureolytic bacteria, cementation solution (urea + calcium chloride) and aggregates. The produced CaCO3 increases with the number of treatments, resulting in better protection and improved inhibition of ASR. The mortar bar specimens using the treated aggregates (6 times) exhibited a significant reduction in the expansion by 55%, with no visible surface cracks. In addition, due to the reduction of micro-cracks, the compressive strength of the mortar bar specimens increased by about 36%.