Self-Healing Coatings for Steel-Reinforced Concrete

Self-healing rebar coatings were prepared and investigated for steel-reinforced concrete, with the goal of creating coatings that can withstand construction site damage. Such damage to conventional coatings results in epoxy chipping or cracking and negates the coatings' ability to resist corrosion. The coatings consisted of a conventional epoxy coating containing 10 wt % microencapsulated tung oil as the healing agent. Upon coating damage, the microcapsules ruptured, releasing tung oil that cured across the damaged area. In accelerated corrosion testing, the times to failure of steel-reinforced concrete with self-healing coatings were at least three times longer than steel-reinforced concrete with conventional coatings. After 150 days of accelerated corrosion testing, 83% of the samples with self-healing coatings exhibited no corrosion. No difference between undamaged and intentionally damaged specimens was observed, potentially because the damaged area was not large enough. These results suggest that natural product-based, self-healing coatings are able to passivate rebar surfaces in response to corrosion initiation, significantly increasing their corrosion protection ability. Pullout testing revealed that self-healing coatings exhibited comparable bond stresses compared to conventional coatings. In summary, this is a promising technology for extending service lives of steel reinforced concrete structures with no reduction in interfacial bonding, which could have significant implications for infrastructure resilience and CO2 emissions.