ANN ARBOR, Mich.— A concrete material developed at the University of Michigan can heal itself when it cracks. No human intervention is necessary?just water and carbon dioxide.
A handful of drizzly days would be enough to mend a damaged bridge made of the new substance. 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. You might need stitches. We?ve created a material with such tiny crack widths that it takes care of the healing by itself. Even if you overload it, the cracks stay small,? said Victor Li, the E. Benjamin Wylie Collegiate Professor of Civil Engineering and a professor of Materials Science and Engineering.
A paper about the material is published online in Cement and Concrete Research. It will be printed in a forthcoming edition of the journal.
In Li?s lab, 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. 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