A critical review on the effectiveness of microbial concentrations for enhancing self-healing in cement concrete and mortar

Abstract

A significant consideration in the design of any structure is the choice of materials. Construction relies heavily on concrete due to its exceptional characteristics and is the primary material used to construct infrastructure across the globe. Moreover, these materials caused micro-cracks under cyclic loading due to tension, significantly reducing their life expectancy. Nowadays, structures have a decreased service life because of the degradation of their durability, strength, and many other attributes. In concrete or mortar structures, cracks are a significant concern as they cause deterioration and allow unwelcome chemicals to enter the system. Sealants and surface treatments have become increasingly popular in enhancing structural appearance in recent years. Despite their limitations, these products are unstable, costly, and contribute to higher pollution levels. When micro-cracks extend and end up inside reinforcement, not only will the concrete be destroyed, but its support will also be corroded by oxygen, water, and harmful gases. Access to the cracked zones may be difficult aside from these operations requiring capital and labour. Crack healing in concrete may be of assistance in reducing the growth and propagation of cracks in concrete. The application of such a concept has led to the development of concrete known as Bacterial Concrete, in which bacteria play the role of carrier and perform bio mineralization by decomposing urea and calcium to produce calcium carbonate (CaCO3), which is capable of filling cracks. Bacteria-induced carbonate precipitation is an environmentally friendly mechanism for autonomously sealing cracks. Many researchers around the world have recently been exploring this mechanism in depth. This paper aims to review the assessment of strength and other properties both in concrete and mortar in relation to specific microbial cell concentrations and to analyse its effectiveness in promoting crack healing and microstructural properties.