Self-healing concrete for more durable structure

April 23rd, 2009 - 4:22 pm ICT by IANS  

Washington, April 23 (IANS) A self-healing concrete has been developed by researchers for safer and more durable structures.
A handful of drizzly days would be enough to mend a damaged bridge made of the new substance, according to a Michigan University study.

Self-healing is possible because the material is designed to bend and crack in narrow hairlines rather than break and split in wide gaps, as traditional concrete behaves.

“It’s like if you get a small cut on your hand, your body can heal itself. But if you have a large wound, your body needs help. We’ve created a material with such tiny crack widths that it takes care of the healing by itself,” said Victor Li, professor of civil engineering.

In Li’s lab, self-healed specimens recovered most if not all of their original strength after researchers subjected them to a three percent tensile strain.

That means they stretched the specimens to three percent beyond their initial size. It’s 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.

“Self-healing of crack damage recovers any stiffness lost when the material was damaged and returns it to its pristine state. The material can be damaged and still remain safe to load.”

Self-healing concrete works because it can bend. When it’s strained, many microcracks form instead of one large crack that causes it to fail, said a Michigan release.

These findings were published online in Cement and Concrete Research.

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