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Concrete In Australia : June 2014
8 Concrete in Australia Vol 40 No 1 NEWS Silver Members Waterproof, malleable and smart Civil engineers at the University of Wisconsin-Milwaukee (UWM) in the US have developed a water repellant, malleable concrete that could see structures free of major cracks for well over a century while reducing maintenance costs. The concrete mix prototype known as Super Hydrophobic Engineered Cementitious Composite (SECC) is significantly more ductile than traditional concrete so that cracks that form do not lead to major issues. Made with additives that change the concrete on a molecular level when the pavement hardens, a microscopic spiky surface is created on the SECC, causing water to bead and roll off. In August last year, a crew of 25 students joined civil engineering graduate student Scott Muzenski, who works with Associate Professor Konstantin Sobolev at UWM, in patching a driveway using the prototype material. In order to track whether the new concrete was performing better than ordinary concrete, electrodes were embedded just below the surface and linked to a data acquisition system. A slideshow of this project can be viewed at <http://bit.ly/1qBsWOA>. “This is going to tell us whether water is getting into the material and how deep it goes,” Muzenski said. “It also detects the presence of chloride ions within the material, and senses load and stress as vehicles pass over it.” Later this year when the software is completed, the real time data will be fed wirelessly into an online repository. According to UWM, SECC also bends without breaking. This is because ultra-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. “Our architecture allows the material to withstand four times the compression with 200 times the ductility of traditional concrete,” Sobolev said. The researchers explained the aim of SECC is not to minimise cracking but to allow multiple micro-cracking. This distributes the load across many tiny cracks too small for water to penetrate. Due to its expense, Sobolev sees the best application for SECC in places where deterioration begins, such as bridge approach decks, but added that the cost would be offset against maintenance and repair costs. He also said SECC could be used with remote monitoring at facilities like nuclear power plants to detect changes. View the video at: <http://bit.ly/1sLwFGR> 08 - News.indd 8 08 - News.indd 8 22/05/14 11:43 AM 22/05/14 11:43 AM