Microbially self healing cement mortar

Abstract

Carbonate-producing bacteria have attracted lots of interest as a promising, natural, environmental friendly novel technique to improvement of concrete characteristics. Considerable research has been conducted on utilizing microbial-induced carbonate precipitation to mitigate several concrete problems such as crack repair, reduction and modification of porosity and permeability. Furthermore, bacterial carbonate precipitation has shown positive influences on compressive strength improvement of concrete. Bacterial concrete is found to be superior in all aspects of durability. In previous studies it is found that bacterial concrete containing 22.5 ml of bacteria is optimum dosage. In the meanwhile, it seems the study related to the exposure in severe environment of bacterial concrete has not been comprehensively investigated. Therefore its decided to carry out an investigation of behavior of bacterial concrete in different severe environment of Chloride and sulphate by forming mortar cubes of bacterial solution 22.5ml/cube and placed in different solution of sulphate and chloride (viz. 5g/lit, 7.5g/lit, 10g/lit, 12.5g/lit, 15g/lit) further these various samples are tested under various laboratory methods (viz. compressive strength, ultra sonic pulse velocity, SEM and mass variation). By doing so, it is found that samples under the different environmental exposures of sulphate and chloride gave the maximum compressive strength of 49.4 MPa in 5g/lit of sulphate and 53.3 MPa in 12.5g/lit of Chloride but these compressive strengths are lesser as compared to conventional cement mortar cubes under same environmental conditions. In this study growth of bacteria is also observed my using mass variation method by observing the weight of samples it is found that the bacteria is growing well in the sample. By performing Ultrasonic Pulse Velocity Test it is found that the quality of cubes are also good.