Autonomous regeneration of concrete structures by incorporation of self-healing mechanisms

As an alternative to the usual strategy of manual r epair of concrete cracks as they arise, concrete elements can be designed with an incorporated selfhealing mechanism. Crack initiation will trigger th e self-healing activity; the repair components are tr ansported towards the location of damage and should heal the crack efficiently. Depending on the type o f structure and the loading situation, the healing material should be able to heal a static or dynamic cra k, and should provide mere crack filling, a re gain in liquid-tightness or recovery of (some of the) me chanical properties. Therefore different self-healing strategies were de veloped, including stimulated autogenous healing by introduction of superabsorbent polymers; autonomous healing by encapsulated calcium carbonate precipitating bacteria; and autonomous healing by a n encapsulated polyurethane-based healing agent. These systems were first tested at laboratory scale for their effects on concrete properties and selfhealing efficiency. Additionally, a large scale lab test was performed on self-healing concrete beams of 150 mm x 250 mm x 3000 mm, loaded in 4-point bendin g mode. Crack formation was monitored with a linear variable differential transformer, acousti c emission, digital image correlation and ultrasoni c wave propagation technique based on embedded piezoe lectric transducers. Crack healing was followed with crack microscopy and water ingress measurement s.