Self-repairing of shrinkage crack in mortar containing microencapsulated bacterial spores

The purpose of this research work was to evaluate the efficacy of microbially induced calcite precipitation (MICP) method in shrinkage crack repairing. Portland cement was combined with sand, bacterial spores, water, and nutrients to prepare self-healing com-posites. The microencapsulated bacterial spores were employed as an additive substance at ratios of 0%, 0.5%, and 1% by weight of cement. Specimens were kept in a climate -controlled room after casting to induce shrinkage crack. Crystalline phases formed in the specimen were identified using the X-ray diffraction (XRD) technique. The scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS) method was used to investigate the morphology of precipitated calcite (CaCO3) crystals. Additionally, the specimen's permeability and compressive strength were also determined. When the bac-terial spores were added to produce MICP procedure, the results demonstrated that it was successful in healing the shrinkage cracking. Within three days, the specimen with 1% spores could completely seal the shrinkage crack. According to the XRD patterns, the CaCO3 crystals appeared to promote the production of the calcite phase. Based on SEM/EDS investigation, the MICP process leads to concentrations of calcite crystal in certain regions, especially at the top surface of the crack. The 28-day compressive strength, on the other hand, decreased, owing to the addition of nutrients.(c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The purpose of this research was to evaluate the effectiveness of the microbially induced calcite precipitation (MICP) method in repairing shrinkage cracks. The study found that the addition of bacterial spores successfully healed the cracks, with the specimen containing 1% spores completely sealing the crack within three days. XRD analysis showed that the MICP process promoted the formation of calcite crystals, while SEM/EDS investigation revealed concentrated calcite crystals in certain regions, especially at the top surface of the crack. However, the compressive strength of the specimens decreased due to the addition of nutrients.