Sustainability assessment, structural performance and challenges of self-healing bio-mineralized concrete: A systematic review for built environment applications

Abstract

The self-healing (SH) of cracks in concrete using bacteria without the need for manual involvement is a viable answer to the problem of long-term concrete sustainability. When provoked, ‘ureolytic bacteria,’ such as Bacillus pasteurii or Bacillus subtilis, which produce ‘urease’ enzymes in the rumen, can produce precipitations of calcium carbonate (CaCO3) in the concrete. Because their cell wall is anionic, CaCO3 accumulates on the surface in large amounts, causing the entire cell to crystallize and eventually clog pores and fissures. This approach of spontaneous induction is an atmospherically beneficial way upon which experts are currently researching. In the present study, the use of bacteriological healing to produce autonomous SH microbial concrete is discussed. It also includes an extensive review of various characteristics of these new concrete types that depict the differences in the auto-addition of various bacteria, as well as an assessment of the healing of cracks because of the addition of bacteria in concrete in a shell that is protective. Relative evaluation methodologies for autonomous and bio-based SH too are reviewed, along with progress, ability, modalities of application, as well as the resulting benefits in terms of durability and strength. The impact of bacteria on the stiffness and compressive strength (CS) of cement paste cubes is also taken into account. The importance of bacteria in microbiologically induced mineral precipitation is also examined using scanning electron microscope (SEM) analysis. Finally, the scope of upcoming investigations and current research gaps are identified and elaborated. Results indicated that the CaCO3 precipitation in the concrete could be attributable to the presence of various ions in the media. Therefore, bio-mineralized concrete has minimized permeability and porosity. The addition of Bacillus subtilis and Sparcious pasteurii species to concrete lessened chloride penetration, enhancing the falling tendency of the sulfate-exposed concrete mass.