Encapsulating immobilized ureolytic bacteria yields self-healing concrete apropos sustainable transportation materials: A review

Transportation networks must be resilient to withstand the effects of climate change and natural calamities. Concrete infrastructure must endure extreme weather, flooding, and seismic catastrophes better than many other types of construction to guarantee the sustainability of transportation services. Self-healing concrete is unquestionably the material of the future that could address these issues. Researchers have discovered a self-healing process in automatic repairing the concrete cracks up to 1.8 mm width. This is made possible by ureolytic and non-ureolytic microorganisms from Bacillus family that cause bacterial precipitation and production of calcite that seal cracks, which could extend the serviceability of concrete. Concrete structures can be restored, and damage prevented through different self-healing mechanisms, such as microvascular healing, bacterial healing, capsule-based healing, and autogenous repair. Research reveals that concrete's capacity to repair itself is greatly enhanced by a mixture of self-healing mechanisms. Moreover, the encapsulation of immobilized bacteria with expanded clay, calcium alginate beads, or other porous materials that can hold onto nutrients and bacteria for an extended period resulted in a considerable improvement in the healing ratio. The main objective of this study is to enumerate all the potential challenges and limitations of the recent studies in self-healing concrete to draw a viable conclusion which is necessary for establishing rules and testing procedures for up-scale implementation.