Self-healing concrete

A concrete material developed at the University of Michigan has the ability to heal itself when it cracks. Its developers claim that just a handful of rainy days would be enough to mend a damaged bridge made of the new substance.

The new material heals itself because it has been designed to bend and crack in narrow hairlines rather than break and split in wide gaps, as traditional concrete does.

Victor Li, the E Benjamin Wylie collegiate professor of civil engineering and a professor of materials science and engineering, is the developer of the new concrete.

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

Li said: 'We found that when we load it again after it heals, it behaves just like new, with practically the same stiffness and strength.'

The engineers found that the cracks must be kept below 150 micrometers, and preferably below 50 micrometers, for full healing. To accomplish this, Li and his team improved upon the bendable engineered cement composite – or ECC – they have been developing for the past 15 years.