A systematic review of bacteria-based self-healing concrete: Biomineralization, mechanical, and durability properties

Cracking is one of the major deteriorating causes of concrete, which allows the entrance of chemicals and can lead to the loss of physico-mechanical and durability properties of concrete structures. To protect, repair, and rehabilitate concrete structures, the application of different surface coating agents and sealants, binding agents, as well as adhesives has been commonly practiced. Although such techniques have mostly been applicable, due to their inherent mechanism difference, major challenges such as delamination and lack of cost effectiveness have resulted in searching for alternative methods of crack sealing or self-healing. One of the novel self-healing mechanisms is using bacterial induced calcite precipitation in concrete mixtures to heal concrete cracks. In this technique, bacterial mineralization (biomineralization) is performed through decomposing urea and calcium to produce calcium carbonate (CaCO₃), which can fill cracks. To review the mechanisms ruling this precipitation, this article aims to present an in-depth analysis of biomineralization, CaCO₃ precipitation, physico-mechanical, durability and microstructural properties of bacterial concrete. To do this, over 70 research articles have been reviewed and their data including the types and dosage of bacteria, mixture proportions, as well as the result of mechanical and durability tests are gathered, provided and analyzed. Based on this review, it is found that the biomineralization is mostly dependent on factors such as the applying method and consistent preservation of the living bacteria. In addition, the environmental impact of bacterial concrete is found to be directly linked with the urea content in the concrete mixture.