Challenging studies of engineered self-healing and self-repairing functions in concrete structures are briefly reviewed. While self-healing of concrete has been studied for a long time, it was only recently noticed that some engineered technologies are useful to stimulate the potential of concrete to be self-healed. For example, fiber reinforced cementitious composites (FRCC) have a much higher potential of self-healing than ordinary concrete because of their capability to keep cracks thinner and also because of the bridging network system in cracks; a specific bio-chemical approach, i.e. the application of mineral-precipitating bacteria, is now available; and various mineral admixtures are useful for practical application. Furthermore, the new concept of self-repairing concrete, which is based on the design concept of intelligent materials, is reported. Self-repairing concrete is concrete that incorporates devices for achieving the three key functions of an intelligent material, (1) sensing, (2) processing, and (3) actuating. This paper is a state-of-the-art report on the recent development of engineered self-healing and self-repairing concrete.
To repair concrete cracks in difficult or dangerous conditions such as underground structures or hazardous liquid containers, self healing mechanism is a promising alternative method. This research aims to imitate the bone self healing process by putting porous concrete internally in the concrete structure to create a porous network similar to ‘spongious bone’. When cracks are formed and detected by sensors, healing agent can be infused into the porous network so as to fill up voids and seal a crack or cracks in the concrete body. This idea was tested using cylindrical and beam samples. A porous concrete core was placed in the concrete specimens. Uniaxial tensile load in the case of the cylindrical samples and bending load in case of beams was applied to create cracks. A healing action was performed by injecting healing agent manually. The results show that a macro-crack is sealed and strength of concrete is regained. Therefore, the concept is considered as to be feasible for self repair mechanism in concrete.
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