News on Nanotechnology

High-performance durable construction materials for roadway pavements are needed for America's increasingly busy highways. In a research project supported by the Federal Highway Administration, a systematic study was conducted of concrete at the micro- and nanoscales to understand the properties of how materials in concrete interact with one another. Nanotechnology research provides the necessary tools for establishing the relationships between the processing, properties, and performance of concrete. The first theme of the research involved understanding the micro- and nanostructures of concrete using advanced experimental tools such as atomic force microscopy and nanoindentation. The second theme is the development of a new type of self-consolidating concrete (SCC) for slipform (SF) paving processes by adding materials such as nanoclays and fly ash to the composition. Third, the researchers are using nanofiber-reinforced concrete to develop the next generation of highway pavements. Fourth, nanotechnology shows promise in the development of smart sensors to monitor the properties of concrete pavement just after it is placed. Nanoscale characterization of cement paste samples showed that the mechanical properties of the C-S-H gel--the glue in concrete--vary in a wide range. Furthermore, the researchers observed that the residual cement particles are almost 10 times harder than the glue produced when mixed with water. This finding signifies that engineers might be able to design the material with the minimum glue necessary to bind the harder particles or phases together. Combining the concepts of particle packing and flocculation, admixture technology, and rheology, the researchers have developed SF-SCC that changes from very fluid to very stiff during the paving process. Preliminary research also has shown that nanofibers and nanotubes potentially can make cement itself super ductile, with more ability to accommodate tension without cracking, which could increase flexural strength significantly.