Case Study: SR 17 and SR 430
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.
The purpose of this project was to preserve pavement on SR 17 & SR 430 in Carroll County near Vaiden, Mississippi. Lehman-Roberts was asked by the Mississippi Department of Transportation (MDOT) to protect 34 miles of existing roadway structure, while improving the ride quality and safety of SR 17 and SR 430. Teams were requested to complete all leveling on both roadways, conduct the placement of ultra-thin overlay on SR 17, finish the permanent striping, and allow normal traffic to resume on SR 17 all by the November 8 milestone date. This project involved the placement of 1” and variable spot leveling with ST, 9.5 mm HMA in order to correct rutting and establish a uniform cross section, as well as the placement of ¾” ultra-thin asphalt pavement.
CHALLENGES & STRATEGY
One of the unique challenges of this project was that it required the teams to use an entirely new 6.25 mm ultra-thin mix design that allows the use of up to 25 percent RAP and 30 percent sand. Due to the use of the ultra-thin lift, the teams were also required to use a special trackless tack coat called eTac®. Tack is the black emulsion that is sprayed on the roadway in preparation for the placement of asphalt. This specific type of tack doesn’t require much heating, cannot be stored for an extensive time in the transport trailer and should be emptied before adding more material to the tank. This calls for constant attention by the distributor truck drivers to avoid clogs that can completely shut down the paving operation. Although this ultra-thin mix was a first for Lehman-Roberts, the design was approved without any problems and ran perfectly throughout the duration of the project. However, the tight timeline required all three Southern Operations crews to work together to ensure its completion ahead of schedule.
Ultimately, this project was a success from start to finish, and work was completed well before the milestone date. Lehman-Roberts executed a change order with MDOT to use clay gravel to dress and spot areas where the shoulders were low. This portion was completed by December 9, 2016. The permanent striping was placed during the spring, and the project was accepted as complete well before the May 31, 2017 completion date. As a result of Lehman-Roberts’ exceptional work on its first ultra-thin project, the company received the Best Thin Lift Overlay in the State by the Mississippi Asphalt Paving Association.