The project called for milling a 15-mile stretch of U.S. Highway 281 to a 2-in. depth, then placing 2 in. of new asphalt, all within a two-month period.
To ensure it could efficiently place the 2 in. of new asphalt and meet TxDOT smoothness and rideability specs, Clark Construction used its Roadtec SP-200 spray paver.
The SP-200 sprays a tack coat seconds before laying the asphalt mix to ensure a good bond to the existing pavement. Spreading augers then deliver the mix from the 11-ton-capacity gravity fed hopper to the Eagle 10 hydraulically extendable, vibrating screed.
Smack dab in the middle of central Texas’ Hill Country lies Blanco County, situated west of Austin and north of San Antonio. The county, with its rugged, picturesque hills with granite and limestone outcroppings, is traversed by the Blanco River and the Pedernales River and two major highways, U.S. Highway 290 and U.S. Highway 281.
The Texas Department of Transportation (TxDOT) has identified a 15-mile stretch of U.S. Highway 281 for significant maintenance. The target stretch connects Marble Falls and Johnson City, with approximately 9,000 vehicles traveling this part of road daily. It also serves as a north-south connection between San Antonio and Lampasas.
The project section of the highway had last received a sealcoat surface treatment in 2002. There was a substantial amount of cracking in the existing pavement surface. TxDOT determined that it was time to perform preventive maintenance before moisture could get into the base material and cause even further damage.
Clark Construction, based in San Antonio, TX, was awarded the approximately $4.7 million project. “When we first arrived on the site, we ran a profilograph to measure the pavement surface roughness,” says David F. Clark, vice president of Clark Construction. “The profile index was in the 80s and 90s, which confirmed the road was in bad shape and needed complete resurfacing.”
The timetable for completing the project was tight. The company had two months to mill and resurface the road with hot mix asphalt. It dedicated 25 employees to the project. Rain delayed the project early on, which created extra pressure to be efficient.
To remove the highway’s rough surface, Clark Construction used a Roadtec RX-700 milling machine from its fleet and acquired a new Roadtec RX-600e. The RX-700 features a three-track assembly and the RX-600e has a four-track assembly. Both models feature 60° conveyor swing to easily feed a truck and 14-in. augers.
“We only needed to mill the highway to a 2-in. depth, so our milling machines had more than enough capacity to easily mill the existing asphalt to the required maintenance depth,” says Corey S. Clark, director of asphalt and fleet operations for Clark Construction. “Our local source, Vulcan Materials, recycled the milled material into the asphalt used to repave the roadway.”
The company used two power brooms and a vacuum truck to thoroughly clean the milled surface before paving began.
Meeting Tough Rideability Specs
Clark Construction used its Roadtec SP-200 spray paver to ensure it could efficiently place the 2 in. of new asphalt and meet TxDOT surface test type B schedule 3 specs for smoothness of ride. In addition, the contractor had to meet density requirements for the material placed.
“The SP-200 spray paver has an innovative design that’s been extremely helpful to us,” says Corey Clark. “On previous jobs, we have experienced a significant amount of savings in time, number of employees required and materials cost.”
In 2004, Clark Construction purchased the first SP-200 manufactured and recently traded it in for a new machine after putting over 10,000 hours on it. The SP-200 features an 11-ton-capacity gravity fed asphalt mix hopper. The 14” x 3/4” spreading augers deliver the mix to the Eagle 10 hydraulically extendable, vibrating screed.
Differing from a conventional paver, the machine sprays a tack coat seconds before laying the asphalt mix to ensure a good bond to the existing pavement. A 500,000-btu heater heats the liquid tack in a 2,100-gal. tank before the paving operation begins. The liquid oil continuously circulates through the system, and an onboard microprocessor controls the rate of flow to the spray bar. The spray bars extend as needed with the screed, and each nozzle can be manually shut off for partial passes.
“The big benefit for us is the machine provides superior bonding to the existing pavement,” says Corey Clark. “The TxDOT inspectors were impressed to see that within seconds of the oil spray that the asphalt was placed.”
Once the 15-mile stretch of U.S. Highway 281 was completed, Clark Construction ran another profilograph to measure the pavement surface. The second profilograph confirmed they had achieved the results they intended — a measurement of 30.
“I’m happy with the finished results on our Highway 281 project,” says Corey Clark. “We achieved a great ride, good quality and the finished road looks great…and we expect it to last 10+ years.” ET