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

Abstract

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 composites. 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 bacterial 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.

Keywords

• Microbially induced calcite precipitation
• Microencapsulated bacterial spore
• Crack closing
• Self-healing concrete