Probing the Abyss: Bacteria-based self-healing in cementitious construction materials – A Review

Abstract

The inclusion of bacteria in developing advanced, self-sensing, and self-healing cement-based materials in crack healing is a sustainable and innovative approach in Civil Engineering applications. As a response to the surrounding environment, the bacterial metabolism leads to microbially induced calcium carbonate precipitation (MICCP). This phenomenon is mostly prevalent with genus Bacillus and other genera. Bacteria being ubiquitous, survive in different environmental conditions, and can precipitate calcium carbonate through different biochemical pathways. Largely, (ureolytic) and (non-ureolytic) bacteria are studied for calcium carbonate precipitation in the cracks and heal them sustainably. Though immense work has been done and published in this domain, the technology transfer from lab-scale to meso-scale has been inefficient due to various factors. Primarily, the bacteria’s specific growth conditions such as optimum pH, temperature, humidity, oxygen availability could limit the translation of this technology to the real-world. Secondly, parameters such as water quality used for mixing of the cementitious materials, curing conditions, incubation time and temperature, and humidity vary from lab to lab causing diverse observations. Thirdly, the BBSHCM's formulation with lab-grade chemicals is expensive. The researchers are exploring alternative nutrient substitutes. Enormous literature ranging from meso to macro-scale studies has been published. This review is a wide-ranging effort to compile the knowledge from published literature on the roles of ureolytic and non-ureolytic bacteria in calcite formation, the problems associated with the delivery of bio-healants at the site of damage, impact of MICCP bacteria on the healing ability and mechanical properties of cementitious material, studies from various field trials, and the economic viability of these systems are discussed and summarised at the end. The aim is to present a comprehensive understanding of the concept of bacteria-based self-healing cementitious material (BBSHCM). To conclude, the variations in results and prospects are recognized and proposed in the final section.