Nighttime work over the next several weekends in a state concrete and bridge repair project on Interstate 75 means contract crews must close some lanes in both directions on a 6-mile stretch between Shallowford Road and a little north of Ooltewah.
The work includes repairs to damaged concrete slabs, bridges and the installation of new pavement markings, according to a news release from the Tennessee Department of Transportation.
After 9 p.m. over the next few weekends, motorists will encounter closed lanes and potential backups surrounding the sections being repaired, TDOT spokeswoman Rae-Anne Bradley said in Thursday's release.
"During this work, the contractor will remove damaged concrete slabs and re-pour them with new concrete, which will require several hours to develop enough strength to carry traffic," Bradley said. "As soon as the concrete cures enough to pass strength tests, the contractor will reopen all lanes to traffic."
This weekend the work started at 9 p.m. Friday and will end at 6 a.m. Monday, according to TDOT.
On southbound I-75, the three outside lanes between mile marker 12.6 and mile marker 6.6 will be closed. Traffic will be shifted to the inside lane and inside shoulder through the project limits, officials said.
On northbound I-75, the two inside lanes between mile marker 6.6 and mile marker 9.8 will be closed, and traffic will use the two outside lanes through those limits.
The area's concrete interstates perform better than asphalt, TDOT Region 2 Director of Operations Ken Flynn said Friday in a statement. Region 2 consists of 24 counties ranging from the Georgia line to the Kentucky line including Bledsoe, Bradley, Cannon, Clay, Coffee, Cumberland, DeKalb, Fentress, Franklin, Grundy, Hamilton, Jackson, Marion, McMinn, Meigs, Overton, Pickett, Polk, Putnam, Rhea, Sequatchie, Van Buren, Warren and White.
"Portland cement concrete roadways are very strong and relatively low-maintenance when compared to asphalt concrete roadways," Flynn said. "However, the constant traffic traveling over the slabs combined with temperature cycling caused by weather - expand in hot, contract in cold - begin to fatigue the slabs and the bases under the slabs, causing failures. These failures show up as cracks, broken slabs or areas where the slabs may sink or move resulting in a bumpy ride."
The repair project involves removal and replacement of the slabs and/or rebuilding the bases supporting the slabs, according to Flynn.
"So we can get many more maintenance-free years from the existing roadway," he said. "These repairs will result in a much smoother ride through the area."
The lane closures last so long because of the way the concrete works.
"Portland cement concrete relies on a chemical reaction to harden," Flynn said. "The concrete being used requires approximately 18 hours after it's been poured to reach a strength of 2,500 pounds-per-square-inch - the strength necessary to support traffic."
The work is weather-dependent, and in the event inclement weather or unforeseen circumstances cause delays, it will be rescheduled to take place as soon as possible, Bradley said.