N.C. StateCivil Engineer Dr. Richard Kim and his graduate assistant researchers put asphalt to the test. They shake it, squeeze it, freeze it, cook it, and pull it.
"We are developing these models so that these models can be used by practitioners to determine which material is better for resisting cracks and also prevent healing," Kim said.
Using sensors, Kim figured out that the binding in asphalt, when given a rest from traffic, actually heals itself. He says a rest of 10 seconds to eight hours could extend a road's life by two to three times.
"If you give it enough time, it will regain its strength almost 100 percent," Kim said.
Kim said asphalt reacts to pressure a lot like silly putty. The surface bounces back well to quick bursts. However, slow, methodical pressure puts a real dent in roads. That is why intersections get most of the potholes.
The doctor's road-kill machine can run its tires over pavement at a high rate of speed simulating long-term traffic patterns. The road can be frozen and thawed in the lab, and a study that may take 10 years gets done in a fraction of the time.
"We can monitor behavior or performance of asphalt concrete pavement within a month," Kim said.
The road crew also tests polymers. They cost more, but they make asphalt more durable to the daily beatings.
In addition to the lab work, N.C. State researchers have also put some local roads to the test. They have studied asphalt durability and ingredients on Highway 70 in Clayton and U.S. 1 in Sanford.
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