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Monday, 13 June 2011

Using Nanosilica to Strengthen Concrete at Stevens Institute of Technology
June 12, 2011

Every day, concrete structures crack and erode prematurely due to Alkali Silica Reactivity (ASR), a chemical reaction that causes fissures in the material as it sets. Jon Belkowitz, a concrete expert and doctoral student at Stevens Institute of Technology, plans to put an end to this problem through his study of chemical reactions within concrete at the nanoscale. Taking advantage of Stevens nanostructure characterization tools and materials, his research into the optimal use of nano silica will create a new concrete mixture that will result in longer-lasting buildings, roadways, sidewalks, stairs, sewers, and dams.

"With the advent of nanotechnology, the material properties of concrete, including ASR mitigation, allows engineers and architects the ability to use concrete in applications that were once impossible," John says.

On the most basic level, concrete is a mixture of finely-powdered cement, rock aggregate, and water. A reaction between the cement and water yields calcium silicate hydrate, which gives concrete its strength, as well as ASR gel. The ASR gel forms at the interface of the alkaline cement and the non-crystalline silica found in the aggregate. As the concrete hardens, the ASR gel expands, causing residual stresses that weaken the concrete and cause it to deteriorate. As pressure builds at the interface, the concrete starts to crack and crumble from within, over a period spanning days to years.

"Using nanostructure characterization tools, we are now able to understand the many mysteries of concrete, for example, that there are three types of water in hydrated concrete, and those three different types of water have three different types of molecular movements, which means three different forces," John says. The more you know about concrete, he notes, the more complex it becomes. He hopes his research will uncover new methods of increasing the mechanical properties of concrete.
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