When the Texas Department of Transportation solicited bids for paving work at Lake Mineral Wells State Park & Trailway, located west of Fort Worth, the original contract specifications called for a hot-mix asphalt design. The Lane Construction Corp.'s Roanoke, TX division proposed a warm mix design and was awarded the contract.
Along with the environmentally-friendly benefits warm mix provides, which was definitely a plus when considering the pristine beauty of the 3,282-acre park, the contractor had logistical issues that only warm mix could address.
According to John Rauer, plant manager for Lane's Bridgeport, TX facility, located approximately 60 miles from the project, hauling hot mix that distance proved challenging.
Another challenge that had to be addressed in executing the project had to do with the tight working conditions in placing asphalt on some of the campsite areas included in the contract. Once mix arrived via 22-ton lowboy trailers, it had to be dumped at a staging area, loaded into tandem dump trucks that could then maneuver the tight paving sites.
And to add yet another challenge, the project was scheduled for construction between November 2008 and March 2009, when cooler temperatures would make it difficult to achieve density specifications with mix hauled a long distance and then transferred into smaller equipment before paving and compaction could actually begin.
Along with repaving numerous campsite and parking lot areas, the Lake Mineral Wells State Park project included reconstructing the main park roadway, which had to be milled, stabilized and then resurfaced with a 2-inch lift of warm mix.
"We had to mill 1 to 3 inches of old asphalt off the park roadway and then treat the flexible (aggregate) base with a cement additive (18 pounds of Portland cement per square yard)," explains Rick Schumann, project superintendent who's been with Lane for 24 years. "We couldn't just mix the old pavement into the base material (which is often done in a full-depth reclamation/stabilization preservation process), because there was a lot of vegetation growing into and out of the old surface."
After mixing the cement additive and water into the base, an 84-inch pad-foot roller was used to compact the material and a motor grader was used to smooth the surface and establish a one percent cross slope from the centerline to each edge.
"We used a sonic tracker to establish and achieve the correct slope before applying an AEP (16,314 gallons of anionic emulsion prime - cut 50/50 to minimize the environmental impact) prime coat over the new stabilized base," Schumann says.
On the campsite pads, Lane expanded the existing paved area by a foot on each side of the pads (replacing soil with Type B 1-in. minus aggregate) before covering the pads with a chip seal prior to placing the new warm mix overlay.
"We had to sealcoat everything (campsite pads, parking areas and roadway) before we could begin paving," notes Rauer, who's been with the company for 27 years. "We used 35,000 gallons of CRS1P (cationic rapid set polymer) emulsion and a Grade 5 (1/2-in. minus) aggregate for the chip sealcoat."
After completing all the preliminary work, the paving crew moved in with a Cat AP-655 8-foot track paver and a Cat AP-1055B 10-foot track paver to begin placing the 17,000 tons of TxDOT Type D warm mix required to overlay the 4.6 lane miles of park roadway, as well as the 87 campsites and parking lot areas. The PG 64-22 warm-mix design, with 3/8-in. minus aggregate and the liquid Evotherm DAT warm-mix additive, was produced at Lane's Bridgeport facility, which is an Astec Six Pack portable plant. The Bridgeport and Justin production facilities support two paving crews, as well as the needs of outside customers.
"We used the smaller paver on the tight campsite areas of the project and the larger paver with extensions on the screed to pave the 20-foot-wide park roadway in one pass," Schumann says. "We achieved our density requirements (92-96 percent) with a rolling pattern that included two Sakai SW900s and one Sakai SW328."