By Colleen Carow and Spencer Elliott
The work of engineers at Ohio University's Ohio Research Institute for Transportation and the Environment (ORITE), part of the Russ College of Engineering and Technology, has saved the state of Ohio an estimated $22 million on road construction over five years.
The engineers found that a material ODOT used to construct new roads in the state wasn't improving pavement performance as expected -- and was actually worsening it in some areas. Based on those studies, ODOT in 2001 stopped using a particular material in road bases, which are sandwiched between the asphalt or concrete pavement and the ground below.
Shad Sargand, a professor of civil engineering at the Russ College and associate director of ORITE, said that at the time, ORITE's recommendation to quit using the material -- called free-draining base (FDB) -- flew in the face of popular opinion. "Our research allowed Ohio to be ahead of the curve during a time when there was widespread pressure to use them in road construction," he said.
Pavement Engineer Roger Green of the Ohio Department of Transportation concurred, saying that the material was recommended as recently as 2001 by the National Cooperative Highway Research Program (NCHRP). "ORITE was one of the first research projects to question the cost effectiveness of the FDB," he added.
The move by ODOT translates to an estimated $22 million saved on pavement construction in Ohio from 2002-2007.
Beyond those millions of dollars, Sargand said taxpayers will continue to benefit from the hidden savings of reduced road repair costs and resultant traffic delays.
Cracks and ruts in the road can come from excessive moisture that causes the ground, or subgrade soil, to soften and sink under traffic loads. FDBs are used to move water off the roadway as quickly as possible -- up to 25 times as fast as a standard base, according to Green.
ORITE's studies, however, found that FDBs didn't, in fact, increase pavement performance when compared with a standard base.
ORITE analyzed roadways around Ohio -- including state Route 2 in Vermillion, U.S. Route 33 in Bellefontaine, and U.S. Route 50 near Athens -- and found that FDB had no effect on keeping the soil underneath the pavement dry. ORITE also led a collaboration of Case Western Reserve University, the University of Toledo, and Ohio State University in a project on U.S. Highway 23 in Delaware that reached similar conclusions.
Engineers learned that existing base materials could drain the water effectively, but a significant amount of water was already present from the water table -- so the FDB didn't prevent moisture. In addition, ORITE learned that FDB can be porous, thus creating potential instability, or it could be very stiff, making it difficult to put concrete pavement on top.
Recent studies, including reports by the NCHRP and the American Concrete Pavement Association, have confirmed ORITE's findings.
Being able to separate road components and analyze them individually was key to ORITE's research. According to Sargand, advanced monitoring and sensor technology now enable researchers to isolate parts of a roadway to measure environmental factors and pavement response.
"In the old days, you couldn't single out each component. Now, with advanced technology, we're capable of looking at the contribution of each," he said. "We came to the conclusion that when you're designing a base, you don't focus only on drainage."
Greene added that nondestructive testing techniques reduce the need to sample and test material from the pavement. "This allows us to test more sites, which leads to more confidence in our conclusions," he said.
The savings generated by ORITE research come at an opportune time for Ohio: The Ohio Department of Transportation is projected to see budget shortfalls for projects in the billions of dollars for the next five years, according to the state agency's estimates. Meanwhile, Ohio is ranked fifth nationally in interstate road length and seventh in total public road length in the United States.
"Once again, the rest of the nation is catching up," Green noted.