Effect of encapsulated bacteria on concrete properties: A review

Abstract Concrete being most abundantly used construction material. However, concrete is weak to resist the tensile forces that leads to cracking, the main reason for its decreased durability and service life. In order to repair the cracks at early stage, different types of bio-based mechanisms like secondary hydration of cement, addition of fibers, encapsulation of bacteria etc. have been adopted. Use of encapsulated bacteria has proved a prominent way for repairing the cracks autogenously in concrete. As bacterium (Genus Bacillus) has the ability to deposit calcite once the favorable conditions are available. The calcite acts as a binder for the cracks and has a higher strength. Different types of carriers have been used for protecting the bacteria from the harsh conditions inside concrete. The encapsulation of bacteria has increased the life span as well as healing efficiency. In this review, the bacterial morphology and growth, the process of Bio-mineralization and the impact of using different encapsulation material for the bacterial immobilization in the concrete have been studied. The effect of encapsulation on the bacteria as well as concrete has also been over-viewed. Based on this, their impact on different properties of concrete like compressive strength, water permeability, healing efficiency etc. has been analyzed. The results obtained from different methods of encapsulation and immobilization carried out through Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) etc. has showed that the healing in concrete has increased to a large extent under favorable conditions. The encapsulation and immobilization technique has proved to be a promising technique in the development of self-healing concrete.