Bacillus cereus GS-5 immobilized sintered fly ash lightweight aggregate for strength, durability, and autonomous crack healing in bacterial concrete

Abstract

<p>This paper investigates the impact of ureolytic bacteria, specifically <em>Bacillus cereus</em> GS-5 immobilized sintered fly ash lightweight aggregate, on the self-healing, strength, and durability characteristics of the bacterial concrete. Different concentrations of bacterial cells (10⁵ to 10⁷ cells/ml) were used, and a part of conventional aggregate was replaced by microbe immobilized lightweight aggregate as part of producing concrete mixes. Various systematic tests, such as compressive strength, water absorption, rapid chloride permeability, and self-healing capability, were conducted after defined time intervals. The results of the experiments demonstrated that the compressive strength of the bacterial concrete increased by an average of 25.65 % as compared to the control specimens. A simulated crack width of 0.5 mm was successfully effectively healed in the specimen by microbial induced calcium carbonate precipitation. The SEM images confirmed the precipitation, structure, and dispersion of the calcium carbonate crystals, whereas XRD analysis revealed the formation of the calcite crystalline phases within the calcium carbonate crystals. Calcite precipitation resulted in reduced porosity of the bacterial concrete, which was confirmed by reduced chloride permeability (5 % - 17 %), water permeability (29 % - 60 %), and water absorption (3 % - 32 %) with respect to the control specimen. It has been concluded that <em>Bacillus cereus</em> GS-5 immobilized sintered fly ash lightweight aggregate would serve as an effective concrete admixture, providing advantages such as self-healing of cracks, better durability, and improved mechanical performances.</p>