The Feasibility of Waterproof Microcapsule System for Bacteria-Based Self-Healing Cementitious Material

In this study, a waterproof material was used to fabricate microcapsule by interfacial curing reaction to encapsulate an alkaliphilic spore-forming bacterium. The technical feasibility of encapsulated spores and the influence of three kinds of curing agent on the calcium precipitation activity (CPA) of the bacterium were studied. Furthermore, micromorphology of microcapsules was observed by Scanning Electron Microscopy (SEM). Afterwards, the thermal stability and thermolysis temperature were determined by TGA thermal analyzer. Moreover, the CPA of broken/ unbroken microcapsules was evaluated. In addition, water resistance was evaluated by adding microcapsules in the water for 1, 3, 7, 14, 28, and 56 days. Finally, light microscope was applied to trace the self-healing behavior of encapsulated mineralization bacterium in cement paste specimens. The results showed that compared with unbroken microcapsules, higher CPA was achieved by breaking the microcapsule to release the bacterium, suggesting good protection for the encapsulated spores. Three curing agents showed nearly similar influence on the spores, while KH792 performed relatively better, and thus was used to fabricate microcapsule with the core/shell weight ratio being 1:1. Our results also indicated that ER microcapsules could keep unbroken in the water for 2 months. Compared with the specimens without embedded bacterium, the healed crack area of specimens embedded with bacterial microcapsules was monitored, suggesting effective self-healing of concrete crack can be achieved by introducing encapsulated mineralization microorganisms into concrete structures. Therefore, we put forward that this waterproof epoxy resin microcapsules could be potential for the application of self-healing concrete.