Use of Bacillus Species Bacteria in Protecting the Concrete Structures from Sulphate Attack- A Review

Abstract

Deleterious ions in the environment such as sulfates may degrade the concrete structures. The interaction of cement hydration products with these destructive agents contributes to severe durability threat of the concrete structures. External sulfate attack is well-known for causing permanent changes in concrete. Microbially induced calcium carbonate (MICP) precipitation has been considered as a unique technique in enhancing the durability properties of concrete. This review paper discusses the possibility of bio-deposition from MICP process as a barrier in microbial treated concrete against the penetration of sulfate ions in a sulfate- rich environment. The effect associated with chemical and physical sulfate attack is discussed in line with the mechanical properties of cement such as compressive strength whereas microscopic evaluation is based on scanning electron microscopy studies. The shortcomings associated with sulfate ions in cement-based materials and the positive effects of incorporating <em>bacillus species</em> bacteria in sulfate rich areas is discussed. This review found that, MICP can significantly reduce the ingress of sulfate ions in cement-based materials, which results in improving the mechanical properties of the cement mortar/concrete.