Bacteria-based self-healing concrete to increase liquid tightness of cracks

Abstract The innovative technology of self-healing concrete allows the material to repair the open micro-cracks that can endanger the durability of the structure, due to ingress of aggressive gasses and liquids. Various concepts of self-healing concrete have been developed, with target on the recovery of water tightness after cracking. Among those, bacteria-based self-healing concrete has shown promising results regarding the improvement of crack sealing performance. In this study, the bacteria-based healing agent is incorporated into lightweight aggregates and mixed with fresh mortar. By this means, autogenous healing of concrete is enhanced and upon cracking the material is capable to recover water tightness. The study focuses on the investigation of the effect of healing agent when incorporated into the mortar matrix and the evaluation of the recovery of liquid tightness after cracking and exposure to two different healing regimes (water immersion and wet-dry cycles) through water permeability tests. It was found that the compressive strength of the mortar containing lightweight aggregates is not affected by the presence of the healing agent. The study also reveals that the recovery of water tightness does not differ substantially either for specimens with or without healing agent when immersed continuously in water. Conversely, the recovery of water tightness increases significantly for specimens containing the healing agent compared to specimens without it, when subjected to wet-dry cycles. Oxygen concentration measurements and bacterial traces on calcite formations confirmed the bacterial activity on specimens containing the healing agent.