Multifunctional, sustainable, and biological non-ureolytic self-healing systems for cement-based materials

Microbially induced calcium carbonate (CaCO3) precipitation (MICP) has been investigated as a sustainable alternative to conventional concrete remediation methods for improving the mechanical properties and durability of concrete structures. To date, urea-dependent MICP is the most widely employed MICP pathway in biological self-healing concrete research as its use has resulted in efficient CaCO3 precipitation rates. NH3 is a byproduct of ureolysis, and can be hazardous to cementitious structures and the health of various species. Accordingly, non-ureolytic bacterial concrete self-healing systems have been developed as eco-friendly alternatives to urea-dependent self-healing systems. Non-ureolytic pathways can improve the physical properties of concrete samples and incorporate the use of waste materials; they have the potential to be cost-effective and sustainable. Moreover, they can be applied in terrestrial and marine environments. To date, research on non-ureolytic concrete self-healing systems has been scarce compared to that on ureolytic systems. This article discusses the advances and challenges in non-ureolytic bacterial concrete self-healing studies and highlights the directions for future research