Hamm Inc. of Perry, KS, served as the primary contractor on the project, placing 585,000 tons of Marshall hot mix design asphalt to construct the new lanes and overlay the existing lanes. A PG 64-28 binder was used in all of the base mix designs and a PG 70-28 binder in all surface mixes. A four-inch BM-2 base course was placed over the aggregated base of the newly constructed third travel lane, followed by a four-inch drainage course. With the drainage course in place, Hamm then placed several lifts (a total of 10 inches) of BM-2C base course, and then capped the entire roadway with two inches of BM-1KTA pavement surface course. Hamm subcontracted the milling portion of the project to Dustrol Inc. of Towanda, KS. Dustrol had to mill 329,619 square yards of existing pavement to invert the slope on the inside lane and shoulder, as well as prepare the existing outside lane to match up the overlay of the existing lanes with the new third travel lane and outside shoulder.
Tony Marienau, asphalt engineer for Hamm, says inverting the slope on the inside travel lane and inside shoulder proved to be the most challenging aspect of the project. With the addition of third lane, KTA engineers did not feel an inside to outside slope design would allow water to drain off the road surface fast enough. Consequently, the project was designed so water would drain off in both directions, allowing the surface to dry off quicker for safer travel.
"We basically had to remove the inside shoulder completely to accommodate the new slope design," Marienau says. "And on the banked curves we had to extend the transition going in and coming out of the curves. So, it required a lot of work to accomplish the correct milling depths required to lengthen the transition areas on the curved portions of the roadway. We also had to place some wedge sections to achieve the correct slope of new road."
The other challenge Hamm paving crews faced in executing the project involved meeting the tight smoothness specification KTA required. To maintain the mix quality and avoid material and heat segregation during placement, Hamm used a material transfer vehicle, which is required on KTA projects, to remix the HMA before sending it to the paver. Hamm used a Roadtec paver, a Roadtec Shuttle Buggy; Caterpillar, Ingersoll-Rand and Hamm rollers to place and compact the new road.
"The material transfer vehicle is critical in preventing material and heat segregation of the mix, but it's also critical in maintaining the pavement operation," Marienau says. "To achieve the smoothness requirements of the project, we had to keep the paver moving. Whenever you stop the paving process, or if you're loading directly from the truck to the hopper, there's always the potential of creating a bump in the mat surface."
Hamm received a $41,000 pavement smoothness bonus on the project, with KTA's smoothness requirements allowing for bonus incentives for surface deviations of less than eight inches per mile and penalties assessed at deviation over 12 inches per mile.
KTA at a glance