by ROY VARNEY
For Reporting Texas
Not everything is bigger these days in Texas, where state highway engineers have developed thinner paving mixes that work better than old-style asphalt coatings, last longer and save the state millions of dollars.
The thinner asphalt overlays, first used on 13 miles of Interstate 35 north of Austin in 2010, will have saved the Austin district of the Texas Department of Transportation $17 million by the end of this season, according to district lab engineer Mike Arellano. The Fort Worth district began using a version on U.S. 287 and Interstate 20 last spring. A project underway near Beaumont will spread the thinner overlay on 20 miles of road — the biggest application so far.
Cutting costs is crucial for TxDOT, which has said it has a $1 billion annual shortfall in what it needs to maintain more than 80,000 miles of roads, including federal and state highways and farm-to-market roads. A proposal on the November state ballot would authorize $1.2 billion annually to fund road construction and maintenance, but that still leaves a big gap.
In 2008, Arellano and Tommy Blackmore, also a TxDOT Austin lab engineer, began developing an asphalt overlay that requires only an inch-thick coating to repave or repair roads – half as much as the usual overlays. Since then, other engineers, including some from the Texas Transportation Institute at Texas A&M University, have developed versions that require as little as a half-inch layer. Ten of the 25 TxDOT districts are using the new mixes, Arellano said.
“It came out of necessity,” Arellano said. “We, like all state agencies, are scrambling for funding, and so it was mainly out of a need to stretch our dollars.”
The recipe mixes high-quality aggregates, or crushed rock, and modified asphalts to create a coating that resists cracks and takes less time to apply, among other advantages.
“This was something that really did appeal to us because it cools quicker, which means we can lay more down and the project length is short,” said Val Lopez, spokesperson for TxDOT in Fort Worth. “Another benefit is, it looks great. It looks absolutely wonderful, and it drives wonderfully well. In fact, we’ve received compliments from motorists about how sharp it looks and how well it drives.”
Tom Scullion, manager of the transportation institute’s flexible pavement program, has been helping districts implement the thin mixes, and said cities and counties have joined the pavement overhaul.
“The trick of the whole thing is that we’re not sacrificing quality, and that’s because we’ve run special tests on the materials before they come down,” he said.
The tests included heating the mix to more than 160 degrees and simulating the beating it would take on the busiest highways.
Scullion said the savings more than make up for the higher cost of the new mixes. He said TxDOT pays about 30 percent more per ton for the materials compared with standard paving, but saves 30 percent per square yard by using the thinner mixes. That doesn’t factor in the fact that the thinner coatings last about two years longer than older products.
Capitol Aggregates Inc. of Marble Falls, which supplies the aggregates, or ground rock, used in the thin overlay to the Austin district, has been having trouble keeping up with demand.
“I’m having to run long hours to produce this material that they want to use to have enough on hand, so the cost is going up on it,” said Brett Ballard, a district manager for Capitol Aggregates.
The Dallas district has not used thin mixes but is monitoring other districts’ use, according to spokesman Tony Hartzel. Arellano said TxDOT still has some work to do to encourage more districts to use the new products.
“We’re trying to address modern-day challenges,” Arellano said. “Now we’re not getting as much money, so we really have to think.”
ROY VARNEY writes for Reporting Texas, a UT School of Journalism program, where this story was originally published. It is reprinted here through a news partnership between Reporting Texas and the San Marcos Mercury.Email | Print