Effect of type of nutrient on crack healing performance of bacterial concrete

Any concrete structure that develops cracks represents a strength failure, and it is an unremarkable observation leading the material attain high permeability and thereby escalating the risk of deterioration. Durability of concrete can be increased by adopting bio-chemical self-healing agents into the concrete. In the current study, an attempt is made to examine the healing tendency of the micro-cracks developed in the concrete by incorporating bacteria of Bacillus species, through the process of biomineralization. Survival of the bacteria is of great concern and it needs to be supplemented by certain nutrients or precursors. Hence this research acquisition, emphasizes the significance of the effect on the addition of nutrients on self-healing performance of bacterial concrete. This paper investigated the effect on healing of the micro-cracks developed in the bacteria based concrete along with the nutrients. In the present work, two types of nutrients viz calcium lactate (1% by weight of cement) and combination of calcium lactate (0.6% by weight of cement) and calcium chloride (0.4% by weight of cement) were intended to analyse their influence on the bacterial concrete specimens. The cultured form of Bacillus subtilis at a required concentration of 5 1x10 cells/mL was added into the concrete matrix, post addition of the nutrients at various dosage in mixing water. The experimentation ensues that there was enhancement on the performance of the bacterial concrete along with increasing curing age period (3,7,14,21,28,56 days) along with conventional concrete. Water absorption and the porosity were diminishing for the bacterial concrete compared to conventional concrete. The maximum healing of the crack width of about 0.8mm at 56 days was observed for bacterial concrete administered with combined nutrient effect.