Sanchez

_{by Vivian F. Cooper}

“Cast in concrete” is not all it’s cracked up to be.

Concrete structures from bridges to condominium complexes are susceptible to cracks, corrosion and other forces of natural and man-made chemical assault and degradation. Aging structures can be repaired, but at significant cost.

Florence Sanchez is looking into the tantalizing world of nanoscience for ways to strengthen concrete by adding randomly oriented fibers ranging from nanometers – roughly the size of four atoms – to micrometers in length and made of carbon, steel or polymers. The assistant professor of civil and environmental engineering at Vanderbilt has won the prestigious CAREER Award from the National Science Foundation for her research on long-term durability of nano-structured cement-based materials.

The award, given to select junior faculty for their exceptionally promising research, provides $400,825 for Sanchez and her associates to study the complex chemistry of nanofiber-reinforced cement-based materials and how these new materials will perform over time in a variety of conditions due to weathering.

“Cement is an ancient material that has been used for centuries, but its chemistry is still not well understood,” Sanchez said. “We mix cement with aggregate to create concrete, which we often reinforce with steel rebar. The rebar corrodes over time, leading to significant problems in our transportation and building infrastructure.”

Sanchez wants to explore how new materials being developed by the nanoscience community might contribute to solving the problem. Nanofibers made of carbon, for example, might be added to a concrete bridge, making it possible to heat the structure during winter or allowing it to monitor itself for cracks because of the fibers’ ability to conduct electricity.

Because nanostructured materials are new, little is known about how they will behave in concrete. “We know that nanofibers improve the strength of concrete at 28 days, but we don’t know how well it resists weathering over the long term,” Sanchez said. “We do not fully understand the chemistry, the mechanisms of interaction, or how molecular-level chemical phenomena at the fiber-cement interface influence the material performance during environmental weathering.”

In addition to analyzing the chemical, mechanical and physical characteristics of the nanofiber-reinforced concrete, Sanchez will give students the opportunity to broaden their educational experience by participating in the research. Undergraduate students at Vanderbilt will be involved in aspects of the research, as will graduate students participating in the Vanderbilt-Fisk Nanoscience Integrative Graduate Education and Research Traineeship program.

“We also will present interactive science engineering activities on the Web for K-12 students to understand how molecular-level chemical changes can affect material properties and performance,” Sanchez said.

The NSF CAREER award will help fund five years of the research, according to Sanchez.

The NSF established the CAREER program in 1995 to help top-performing scientists and engineers early in their careers to develop simultaneously their contributions and commitment to research and education.

_{Posted 12/12/05}