Mechanical and durability properties of self-healing concrete containing carbonate precipitation bacteria immobilized in perlite

Today, self-healing materials are used as intelligent materials in improving the properties of structures in many industries. One of the methods of self-healing in concrete is the use of calcium carbonate precipitation mechanism due to microbial activities. This research evaluated the effects of a specific strain of Sporosarcina pasteurii bacteria as a new method on the mechanical and durability properties of self-healing concrete. For this purpose, perlite aggregate was used as a carrier, and bacteria were immobilized in it.Five different cell concentrations (1.5×109, 2.6×109, 4×109, 5.2×109, 6.7×109 cfu /ml) of bacteria were used in the concrete mixtures and compared with a control mixture without bacteria. The compressive strength, tensile strength, water permeability, and chloride ion penetration at the age of 7, 28, and 90 days were tested. Also, the microstructure of some mixtures was investigated by Scanning Electron Microscope. The test results demonstrated that the use of Sporosarcina pasteurii immobilized in perlite improved the compressive and tensile strength, reduced the permeability of concrete. Maximum increase (23%) in compressive strength was measured with 2.6×109 cfu/ml of bacteria.