Bacteria encapsulation using synthesized polyurea for self-healing of cement paste

Cracks in concrete increase permeability and exacerbate the detrimental effects of weathering and potential chemical attacks. Common repair techniques involve the use of sealant agents or utilization of biotechnology methods that can self-heal the cracks. In this study, a polyurea polymer because of its adaptable mechanical properties needed for encapsulation (e.g. moisture barrier and spore immobilisation) and its fast curing reaction is proposed as a potential suitable shield and carrier for Bacillus pseudofirmus to produce calcium carbonate (CaCO3) crystal. Synthesis and encapsulation of the bacteria in the polyurea were performed using in-situ polymerization. Chemical characterization and microstructural analysis of the produced polyurea capsules show that the Bacillus pseudofirmus bacterial spores and nutrition were successfully encapsulated without affecting its chemical structure. The bacterial growth further was confirmed by integration of several morphological analyses. The polyurea microcapsules carrying the bacteria were well-mixed in a cement paste. The hardened specimens were cracked using a three-point bending apparatus to artificially trigger the healing effect of the bacteria capsules. The morphology and chemical characterization confirmed precipitation of calcium carbonate around the cracked zone. Polyurea encapsulation was found to be a practical approach to protect bacteria included in cementitious material for the purpose of self-healing.