Application of bacterial biomass in biocementation process to enhance the mechanical and durability properties of concrete

This study presents the results from the microbiological induction of bacterial biomass (i.e. biocementation) in concrete mixtures to enhance the mechanical and durability properties. Bacteria isolated from manufactured sand (i.e. bacillus megaterium) were incorporated into concrete mixtures and the corresponding effects on the mechanical and durability properties were investigated. The influence of the bacteria concentration was assessed in terms of compressive strength, split tensile strength, flexural strength, acid resistance, chloride ion penetration and water permeability. In addition, microstructural investigations were also carried out. Findings from this study indicated that the compressive strength, split tensile strength and flexural strength of concrete made with 105 cells/ml of bacteria is 11.3%, 97.5% and 10.7%, respectively. Similarly, concrete made with 105 cells/ml of bacteria exhibited lower permeability (i.e. lower chloride ion penetration and water permeability) and higher resistance to acid attack compared to the plain concrete without any induced bacteria. The improvement in the properties of the concrete with the incorporation of bacillus megaterium was associated with the precipitation of calcite and the presence of bacterial biomass within the pores of the concrete matrix. Microstructural investigations also showed that concretes made with bacteria at a concentration of 105 cells/ml have more calcite formation as evident in the scanning electron microscopy images and elemental composition of the concrete. Hence, it was concluded that the use of the bacillus megaterium at a concentration of 105 cells/ml is optimum to achieve enhanced performance of the concrete.