Paving the Way for Better Roads Ahead


Rafiqul Tarefder researches better materials for building roadways

Each mile of road in New Mexico costs between $500,000 and $1.5 million to build. Multiply those amounts by more than 27,800 lane miles of paved roadway in the state, and you start to get a sense of just how much the New Mexico Department of Transportation (NMDOT) spends on building and maintaining the state’s highways and byways.

Rafi Tarefder, associate professor of civil engineering, is applying his expertise in pavement materials and design to change the roadway construction industry. His findings help government agencies, including NMDOT, build and maintain better roads — and save money in the process. “Based on the structural design of a road, one can save up to $100,000 per mile,” explains Tarefder.

To conduct his research, Tarefder has developed four labs at UNM Engineering: the Advanced Pavement Testing Lab, the Materials Processing Lab, the Hydraulic-Pavement Lab, and the Asphalt Binders Lab, one of the few of its kind in the nation. Using state-of-the-art equipment and with research support from his graduate and undergraduate research assistants, Tarefder is pursuing several research projects.

In one research project funded by a National Science Foundation CAREER award, Tarefder is trying to resolve a long-standing industry problem: how moisture damage occurs in asphalt and whether the damage happens between layers in the pavement or within binders in the material. Tarefder uses an atomic force microscope and nanoindenter to study adhesion and stiffness of the materials at a nanoscale level and then extrapolates those findings at the macro level. His research showed that moisture damage occurs in asphalt binders even with the presence of antistripping agents, additives that are used to reduce moisture damage in pavement. The research also demonstrated that lime is a better anti-stripping agent and is more effective in fighting against moisture compared to other agents, including chemical antistrips.

Tarefder is also researching ways to engineer better pavement. “In the past, NMDOT pavement design was based on an empirical approach, relying on experience and equations developed from road test data of the ‘60s,” he says. “Now we use advanced mechanics, testing, and computation.”

Tarefder has been instrumental in calibrating and implementing the Mechanistic Empirical Pavement Design Guide (MEPDG), a national pavement design guide, in New Mexico. The MEPDG uses local materials information, traffic conditions, and climate data for efficient pavement design. But before the MEPDG could be implemented in New Mexico, it had to be customized with certain parameters specific to the state — including approved materials and failure criteria. Tarefder is leading that initiative, which will have a big impact on the state — and residents’ wallets. “The calibrated MEPDG will save designers and taxpayers a lot of money.”

UNM Regents’ Lecturer Award, 2011

UNM Engineering Junior Faculty Research Excellence Award, 2010

NSF CAREER Award, 2007