MURFREESBORO, Tenn. (WKRN) — Researchers are working to find quicker, more cost-effective ways to improve road construction and reduce potholes.

Middle Tennessee State University School of Concrete and Construction Director Dr. Kelly Strong said the potholes that popped up in Middle Tennessee this winter did not come as a surprise. He said one factor has been our weather pattern with a bad winter causing lots of freeze and thaw cycles. Dr. Strong explained that when there’s any cracking in the surface, and all that rain gets down, and then freezes, it just pops off the overlay.

“Increased traffic, especially on the interstates which carry a lot of trucks, a lot of heavy freight, they do damage to the pavement,” Dr. Strong explained, adding that the impact is not linear and that doubled traffic means doubled road damage, but instead there are 8-10 times the road damage. “It’s like bending a coat hanger. The pavement flexes every time a car passes over it or a truck and trucks do more damage than cars. So if you think about bending a coat hanger, you bend it five times it’ll probably still hold up your sweater, but you bend 55 times it’s not going to be any good anymore. So the more flexure there is, the more frequently it flexes, the faster it wears out, and then that overlay pops off again.”

He said the construction of roads in Middle Tennessee has also played a factor in increased potholes.

“I checked with some local experts and they report that virtually none of the major freight corridors through Middle Tennessee have concrete pavements. The U.S. interstate system is 60 percent concrete, and higher in urban freight corridors,” stated Dr. Strong. “Many states, including Illinois, California, Washington, and Minnesota have moved to require Long-Lived Concrete Pavements for their major urban freight corridors. These types of pavements have design lives of 40-50 years compared to 20-25 years for full-depth asphalt and 7-10 years for a well-constructed asphalt-bonded overlay. The life of a pavement is impacted by traffic volumes, the number of heavy trucks, and maintenance practices.”

However, he said many departments of transportation continue using asphalt because it’s quicker and cheaper than concrete.

“[Nashville residents] better be prepared for years and years of traffic headaches because it takes more time to do that,” said Dr. Strong, adding that when a road repair takes a long time, then what experts call ‘road user costs’ go up with traffic delays and detours, all impacting the public. “During construction, the road user costs of concrete pavement are going to be higher because that section of the road’s probably going to be closed quite a bit longer. Full depth, asphalt — so now we’re not just stripping off the top two inches, we’re taking all that old asphalt out and replacing it — the hot-mix asphalt full depth doesn’t last as long as a Portland cement concrete pavement, but it is cheaper and faster.”

He says they’re researching to find more effective solutions for road construction that don’t sacrifice cost. For instance, researchers want to see if a concrete pavement is nearing the end of its life around 40 years old. They pulverize that concrete pavement and mix it back into a fresh batch of materials to reduce the cost and speed up the construction process.

“Aggregate can be different sizes and different types of different geology,” Dr. Strong said. “Here in Middle Tennessee, we’re pretty blessed with abundant supplies of limestone, which is a very good aggregate. In other places in the state, it’s hard to get that and it’s not economically viable to truck good aggregate very far; it gets really expensive in a hurry. So you kind of use whatever aggregate is available, and that’s why we’re testing different pavements from different places.”

Dr. Strong said they’re also working to research mixing polymer fibers in to try to reduce the deflection in the pavement and the wear.

“That research is coming and that might help us solve some of the jointing problems that we have experienced, not in Tennessee necessarily, but just all over the country with concrete pavements,” he explained.

Another factor to consider in all this research is the increase in changing weather patterns because that ages the pavement.

“Most of the pavement design guides are based on historical weather records, historical climate records that may not be an accurate reflection of future climate trends. So almost all engineering models on the material are based on previous performance research,” said Dr. Strong. “And if the weather models, if the weather data that we use to design things is no longer reliable, then we have unexpected or unanticipated problems that come up in the future.”