Advanced Concrete Means Little Maintenance For A Century

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A new water-repellant concrete impregnated with tiny superstrong fibers promises to leave roads and bridges free of major cracks for up to 120 years.

University of Wisconsin-Milwaukee civil engineers have developed a concrete mix that is durable and superhydrophobic. They call it Superhydrophobic Engineered Cementitious Composite (SECC). Preventing normally porous concrete from absorbing water means that liquid can’t get inside, freeze and cause it to crack. The concrete’s unusual characteristics, including being significantly more ductile than traditional concrete, means that cracks that do form do not propagate and cause failure.

“Our architecture allows the material to withstand four times the compression with 200 times the ductility of traditional concrete,” said associate professor Konstantin Sobolev, whose lab created SECC.

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To impart the characteristics in the material they wanted to see, they doped their mix with superhydrophobic additives based on siloxane, a compound that forms the backbone of silicones, mixed with superfine powders. Together, these form a microscopic spiky surface nearly impermeable to water. They also added unwoven polyvinyl alcohol fibers, each the width of a human hair, which are strong enough to let the concrete bend without breaking. 

“The use of polyvinyl alcohol fibers in engineered cementitious composite proves to be a very effective method to not only improve the ductility of concrete, but to drastically improve its durability,” the researchers wrote in a June 2013 report on SECC. “Conventional reinforced concrete is a relatively brittle material which, when loaded, typically causes large cracks. These large cracks allow water to penetrate through the concrete, reaching the reinforcing steel and, in turn, cause the steel to corrode, ultimately leading the failure of the reinforced concrete.”