Survey of Indigenous Bacteria as a Simplified Alternative to Produce Self-Healing Cementitious Matrices

The cracks in concrete serve as pathways for aggressive agents, leading to deterioration. One approach to addressing these cracks and enhancing structures durability is the use of self-healing agents, such as bacteria used to heal cracks in cementitious matrices. Bacteria can be found in several environments, and their identification and healing viability must be evaluated prior to their use in cementitious matrices. In this study, distinct indigenous bacteria were collected from soil in industrial yards associated with the cement industry. These bacteria were identified and incorporated in cement and mortar mixtures with 18% entrained air. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were performed to characterize the formed products, and compressive strength testing was conducted to evaluate the mechanical properties of the mortars. The identified bacteria were of the genus Cronobacter, Citrobacter, Bacillus, and Pseudomonas, and their potential to form self-healing products was evaluated with microscopic and mineral analyses. Results showed that all bacteria could form calcite (CaCO3) crystals, with full crack healing in some of the samples. Mechanical testing indicated increases in average compressive strength of up to 108% at 28 days with respect to a reference mortar.