By Cameron Chai
According to concrete specialist at Stevens Institute of Technology, Jon Belkowitz, the cracking and eroding of concrete structures can be prevented using his research on chemical reactions taking place in concrete at the nanoscale level.
Jon utilizes nanostructure characterization materials and tools from Stevens to study the best possible use of nano silica to form a new concrete composition that will result in strong roadways, buildings, stairs, sidewalks, dams, and sewers.
Jon stated that with the development of nanotechnology, concrete’s material properties, including ASR mitigation, enables architects and engineers to use concrete in applications that were not possible in the past. He explained that with the use of nanostructure characterization tools, it has been possible to comprehend the various mysteries concerning concrete. For instance, hydrated concrete features three types of water, which has three distinct types of molecular motion offering three different forces, says Jon. He hopes to devise new techniques to improve the mechanical properties of concrete.
Concrete is obtained by mixing rock aggregate with finely-powdered cement and water. The cement reacts with water to form calcium silicate hydrate, which renders strength to concrete, in addition to ASR gel. The ASR gel is formed at the boundary of the aggregate’s non-crystalline silica and alkaline cement. As the concrete solidifies, the ASR gel undergoes expansion, resulting in residual stresses that can deteriorate the concrete structure. With an increase in pressure at the interface, the concrete begins to break and disintegrate over a period of time which may span from several days to even years.
Jon explains that with the use of nanotechnology, he can not only prevent the production of ASR but also utilize nano silica to reinforce the hydrated cement matrix of concrete to fight the expansion of the ASR gel. He mentions that he hopes to alter the characteristics of the extra water within concrete to stop it from reacting with soluble alkaline to produce ASR gel.
It is not easy to control the reactions taking place within concrete as it solidifies and strengthens. It was hard to comprehend the growth of the crystallgraphic grains present in the concrete structure. With the use of nanostructure characterization tools, scientists can understand the hydrated cement matrix that forms concrete in an effective manner.