ACPA Quarter 3 2019

www.acpa.org Quarter 3, 2019 7 I - 8 5 U N B O N D E D O V E R L A Y continues on page 8 » E. Boyd Tharrington, P.E., Division Construction Engineer for Division 5 of the North Carolina Department of Transportation. Over the last decade, truck traffic has increased steadily. This section of I-85 currently carries nearly 40,000 vehicles per day (VPD), with 23% of all traffic consisting of trucks. According to FHWA’s office of Freight Management and Operations, freight truck traffic is expected to increase by another 40% in the next 30 years, which will mean that I-85’s average truck traffic will be over 12,800 trucks per day. The 10-in. unbonded concrete overlay is placed on top of an asphalt in- terlayer, says Adam Bruner, Carolinas Regional Manager for McCarthy Improvement, an ACPA member. “We paved over 80 lane miles—just over 21 miles of two northbound lanes and two southbound lanes,” he explains. Almost 662,200 SY of concrete was used, making it one of the largest unbonded concrete overlay projects in the southeast. When this section of I-85 was first paved, standard design specifica- tions called for 30-ft joint spacings with no dowel bars to transfer loads between slabs. “Now, the joint spacing is at 15-ft and dowel baskets were placed,” explains Bruner. The current design produces a pavement that can handle the expected volume and type of traffic expected in the future, he adds. Although the concrete contractor was able to work on two-lane sections throughout the project, with traffic diverted to one lane each way on the other side of I-85, space in the work zone was tight. “Stringless paving was a lifesaver for us on this project,” says Bruner. “There were a number of opera- tions in the work zone at one time, so there was no room for a stringline.” “This was the first time stringless paving has been used in a project I’ve handled,” says Tharrington. “It provided a great advantage in access through work areas, getting material to the paver, and improving overall safety on the site.” Although a constricted work zone is a challenge, the greatest challenge faced was the acceleration of the project schedule two years into construc- tion. “One of our department initiatives is to identify major projects that D E M A N D S F R O M I N C R E A S E D T R A F F I C continues on page 8 »