April 22, 2009

Scientists develop self-healing concrete

U.S. scientists say they have developed a concrete material that can heal itself when it cracks with only water and carbon dioxide needed.

University of Michigan researchers said all that is necessary to mend a damaged bridge would be a few drizzly days. They said the self-healing is possible because the concrete material is designed to bend and crack in narrow hairlines, rather than break and split in wide gaps, as does traditional concrete.

Professor Victor Li, who led the research, said self-healed specimens recovered most, if not all, of their original strength after researchers subjected them to a 3 percent tensile strain. That means they stretched the specimens to 3 percent beyond their initial size -- the equivalent of stretching a 100-foot piece an extra three feet -- enough strain to severely deform metal or catastrophically fracture traditional concrete.

We found, to our happy surprise, that when we load it again after it heals, it behaves just like new, with practically the same stiffness and strength, Li said. The material can be damaged and still remain safe to load.

The research is available online, ahead of print, in the journal Cement and Concrete Research. Li will also present the research in Chicago during June's International Conference on Self-Healing Materials.