Comparative performance of different bacteria immobilized in natural fibers for self-healing in concrete

Abstract Carrier compounds besides the type of bacteria for microbial induced calcite precipitation are equally important in self-healing concrete. This study investigates the potential utilization of natural fibers namely, coir, flax, and jute fibers to carry bacterial spores for self-healing in concrete. The comparison is drawn for introducing calcite precipitation bacteria namely Bacillus subtilis KCTC-3135T, Bacillus cohnii NCCP-666, and Bacillus sphaericus NCCP-313 in concrete along with calcium lactate pentahydrate and urea as organic nutrients. The findings from visual, microstructural, and mechanical properties of self-healing concrete suggest that natural fibers were capable of substantial immobilization potential for bacterial spores. Flax fibers provided better protection to bacteria with improved crack-healing and regain in compressive strength, whereas coir fibers resulted in higher compressive strength. It is also observed that B. sphaericus NCCP-313 precipitated more calcium carbonate as a healing product with uniform healing in the entire length of cracks in concrete. Consequently, approximately 75–85% and 60–65% healing rates were attained by fiber immobilized bacteria in 7 days and 28 days pre-cracked specimens, respectively.