Now, crack-proof concrete that can last a lifetime

Scientists claim to have developed a new crack-proof 'smart' concrete with an estimated life span of more than 120 years.
The cement composite developed by scientists from the University of Wisconsin-Milwaukee (UWM) is a durable, water-resistant and malleable paving material with a high level of "crack control".
The average life span of concrete roads in Wisconsin falls in the 40-50-year range, with up to 10 per cent of reinforced bridge decks needing replacement after 30 years, researchers said.
A crew of 25 students joined Scott Muzenski, in patching the driveway using the unique material.
In order to track whether the material was indeed holding up better than ordinary concrete, they gave the 4-by-15-foot slab the ability to monitor its own performance.

About an inch below the surface, the students embedded electrodes in this 'smart' concrete that are linked to a data acquisition system located behind an adjacent retaining wall.

"This is going to tell us whether water is getting into the material and how deep it goes. It also detects the presence of chloride ions within the material, and senses load and stress as vehicles pass over it," said Muzenski.
When the software is completed, the real-time data will be fed wirelessly to an on-line repository.
"We'll be able to observe the performance of concrete as it happens, in real time," said associate professor Konstantin Sobolev.

Researchers are now confirming two important features of this hybrid concrete called a Superhydrophobic Engineered Cementitious Composite (SECC): its superior durability and its 'smart' capability.
Researchers point to two reasons they believe SECC is a superior material. First, it contains compounds that make the material nearly waterproof.
As Sobolev squeezes an eyedropper of water over a small piece of the hybrid concrete, the liquid beads up on contact into almost perfect spheres that rush off the hard surface at the smallest tilt.
Additives in the hybrid change the concrete on a molecular level when the pavement hardens, creating a spiky surface that, although microscopic, causes the water to bead and roll off.

The second innovation of SECC allows the material to bend without breaking. Sobolev's lab has improved ductility with their composite.
Super-strong unwoven polyvinyl alcohol fibres, each the width of a human hair, are mixed into and bond with the concrete. When cracks begin, the fibres keep them from becoming larger tears.