Why are there so many potholes in Tennessee?

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

Director of Middle Tennessee State University’s School of Concrete and Construction, Dr. Kelly Strong, said the potholes that appeared in Middle Tennessee this winter weren’t A suprise. He said one factor has been our weather pattern with a bad winter causing many cycles of freezing and thawing. Dr. Strong explained that when there are cracks in the surface, and all that rain falls and then freezes, it just comes off the overlay.

“Increased traffic, especially on highways that carry lots of trucks, lots of heavy goods, damages the pavement,” Dr Strong explained, adding that the impact is not linear and doubled traffic means double road damage, but instead there is 8-10x more road damage. “It’s like bending a coat hanger. The pavement sags every time a car drives over it or a truck and trucks do more damage than cars. So if you’re thinking of folding a hanger, you bend it five times, it’ll probably still hold your sweater, but you bend it 55 times, it won’t do any good. So the more flex it has, the more frequently it flexes, the faster it wears out, and then that overlay comes off again.

He said road construction in central Tennessee also played a role in the increase in potholes.

“I’ve checked with some local experts and they report that virtually none of the major freight corridors through Middle Tennessee have concrete pavement. The US interstate system is 60% concrete, and more in urban freight corridors,” said Dr Strong. “Many states, including Illinois, California, Washington and Minnesota, have decided to require long-life concrete pavements for their major urban freight corridors. These types of pavements have a design life of 40 to 50 years, compared to 20 to 25 years for full-depth asphalt and 7 to 10 years for a well-constructed asphalt binder. The life of a pavement is influenced by traffic volumes, the number of heavy trucks and maintenance practices.

However, he said many transport departments continue to use asphalt because it is faster and cheaper than concrete.

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

He says they are researching to find more efficient solutions for road construction that don’t sacrifice cost. For example, researchers want to see if a concrete pavement is nearing the end of its life at around 40 years old. They pulverize this concrete pavement and mix it into a new batch of material to cut costs and speed up the construction process.

“Aggregates can be different sizes and different types of different geology,” Dr Strong said. “Here in central Tennessee, we are fortunate to have abundant reserves 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 fast. So you kind of use whatever aggregate is available, and that’s why we test different coatings in different places.

Dr Strong said they were also working on research into blending polymer fibers to try and reduce pavement deflection and wear.

“This research is coming in and it could help us solve some of the assembly problems that we’ve had, not necessarily in Tennessee, but across the country with concrete pavements,” he explained.

Another factor to consider in all of this research is the increase in changing weather conditions, as this causes the pavement to age.

“Most pavement design guides are based on historical weather records, historical climate records that may not accurately reflect future climate trends. So almost all of the engineering models on the material are based on past performance research,” Dr. Strong said. “And if the weather models, if the weather data that we use to design things is no longer reliable, then we have unexpected or unforeseen problems that arise in the future.”

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