Case Study: Hwy. 315 Project

Lehman-Roberts Co., now in its fourth generation of ownership, continues to build upon a long tradition of quality, trust, and strong managerial leadership that sets it apart from competitors in the highway construction industry.

SITUATION

The purpose of this project was to provide a full-depth reclamation of 9.36 miles of Highway 315 in Panola County, MS. The stretch of reclaimed roadway began at the intersection of US 51/Highway 315 and proceeded west. In providing a full-depth reclamation, the Lehman-Roberts goal was to take a badly deteriorated section of road, comprised of a granular material base and five inches of aged/stripped asphalt, and build it back up to a safe and navigable route. The end result needed to be a roadway that could stand the test of time. In addition, this project was part of a larger exploratory pilot venture for the Mississippi Department of Transportation (MDOT). The intention was to use project findings to rebuild other three-digit routes that had failing or underperforming subbases within District 2.

SPECIFICATIONS

MDOT requested that the project be constructed according to the 2017 Edition of the Mississippi Standard Specifications for Road and Bridge Construction. Our team began by pulverizing and mixing the subgrade/asphalt to a depth of nine inches – five inches of stripped asphalt and four inches of granular material. Then, the team incorporated 6% by volume of cement to the mixture for a width of 28 feet. Next, we chip sealed the previously soil-cemented subgrade within three days of completion. Our team overlaid the chip seal with two inches of 12.5mm ST Hot Mix Asphalt. Lastly, we completed a ¾-inch ultra-thin course for the riding surface.

CHALLENGES

Due to heavy canopy cover from the trees over the roadway, it was hard for the GPS equipment to stay affixed to the satellites that maintained the controls of construction equipment. In addition, this section of roadway is a heavily traveled trade route with a mixture of agriculture equipment and heavy transport vehicles. Communication was imperative so that tractor trailer trucks had enough advance warning to take an alternative route, as opposed to them running through construction operations.

STRATEGY

Lehman-Roberts joined forces with Kimes & Stone, who were pivotal in ensuring project success with their soil cement for the pavement base. With this being a heavily traveled route, it made sense to split the project into three sections to minimize exposure to the residents living along the route. This allowed our team to simultaneously grant and maintain access for the residents to have a means of ingress and egress. The Mississippi Department of Transportation expectations were to have a roadway that, after being chip sealed, met a smoothness tolerance of 50% better than the preceding riding surface, which was, on average, 200 inches per mile.

To ensure we could exceed this criteria, Lehman-Roberts elected to place the two inches of 12.5mm ST in two separate lifts (½-inch of leveling and 1½-inches of binder). This took a section of roadway that required a minimum of 100 inches/mile to below 50 inches/mile. We feel that the leveling lift was a crucial part of this success because it eliminated all irregularities that occurred in the chip seal surface due to the heavy usage of the roadway during construction.

RESULT

Lehman-Roberts Co. completed paving seven days ahead of schedule on April 21, 2020. The existing roadway that began with Mean Ride Index (MRI) scores reflecting rough pavement now reflect significant improvement. This is recognized in the finished project, with 97% of the right lane and 96% of the left lane measuring within the interstate standard of 60 inches/mile (down from the original totals of 122.93 and 140.26, respectively). The Mississippi Department of Transportation was presented with a reconstructed section of road that met their requirements and exceeded both the owner’s and contractor’s expectations.

Not only was this project a success with MDOT, but also it received state-wide recognition from the Mississippi Asphalt Pavement Association (MAPA) at the association’s annual 2020 conference. It was awarded a Quality Asphalt Award in the category of “Best Small New Construction/Reconstruction.”

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