Bio-induced carbonate precipitation in concrete and mortar: CaCO₃ localization and engineering performance

Calcium carbonate (CaCO₃) precipitation within concrete and mortar has emerged as a promising approach for improving mechanical performance, sealing cracks, and enhancing durability through in-situ mineral formation. In cementitious systems, bio-induced carbonate precipitation enables CaCO₃ to form within pores, cracks, and other microstructural features, thereby modifying load transfer and transport pathways without additional cement consumption. This process is commonly achieved through microbially induced carbonate precipitation (MICP) and enzyme-induced carbonate precipitation (EICP), which differ in biological complexity but generate comparable carbonate phases within the cementitious matrix. Recent studies have further integrated industrial by-products, including fly ash, slag, cement kiln dust, red mud, and recycled concrete aggregates, as calcium sources or nucleation-active substrates, linking bio-cementation with waste-derived cementitious materials. Despite extensive research on CaCO₃ formation in bio-cemented materials, reported improvements in strength, crack-healing efficiency, and durability remain highly inconsistent across the literature. This review critically examines bio-induced carbonate precipitation in concrete and mortar by linking precipitation pathways to structure–property relationships and engineering performance, rather than evaluating CaCO₃ yield as an isolated metric. Evidence across the reviewed literature indicates that engineering improvements depend primarily on the spatial localization, continuity, crystal morphology, and mechanical integration of CaCO₃ within the cementitious matrix. Controlled precipitation within pores and cracks was consistently associated with strength recovery, autonomous crack healing, and reduced permeability. By synthesizing microstructural evidence, precipitation pathways, and engineering performance outcomes, this review establishes a framework for interpreting and designing bio-cementation systems that translate mineral formation into reliable structural benefits.