Paving the way

Engineer explores ways to give Texas drivers smoother roads

by Analisa Nazareno

Along Texas’ nearly 41,000 miles of rural roads, a motorist is likely to encounter crisscrossing cracks up and down a good amount of the asphalt pavement.

Texas has the largest network of rural roads in the nation, and much of that network rests on vexing clay soil. This expansive soil wreaks havoc on roads as it swells when it gets wet and shrinks as it dries out. And the sustained heat of Texas’ long summers, which softens the asphalt and makes it vulnerable to rutting and cracking, compounds the problem.

Samer Dessouky will be spending much of the year ahead finding the most viable and cost-effective solutions to fix the pockmarked and fractured roads. Dessouky, an assistant professor of civil engineering, is leading a team of researchers that includes faculty members at Texas A&M University and Lamar University on developing routine maintenance strategies for the Texas Department of Transportation (TxDOT).

“TxDOT is currently experiencing edge-cracking problems for their FM [farm-to-market rural] roads, especially on the east side of Texas, and they put up a problem statement to the researchers on how they can solve it,” Dessouky says.

Dessouky has received funding from TxDOT and UTSA to explore the best solution to rehabilitate the roads. Some of the roads could be fixed by adding fly ash or hydrated lime to stabilize the clay soil. Or the best solution might be to lay a special geogrid fabric between the soil and base layer to protect the roads from the clay movements. Other solutions could be adding more layers of asphalt on top of the road or extending the shoulder on the sides of the road.

Dessouky will be working with researchers from the Texas Transportation Institute (TTI) at Texas A&M University, where Dessouky earned his doctorate in civil engineering in 2005, specializing in asphalt materials research.

They will utilize ground-penetrating radar equipment to analyze the road foundations and the soil underneath for this rural road repair strategies project. They will also analyze TxDOT’s Pavement Management Information System database. The database collects real-time survey photos of roads within the TxDOT system.

“Joining forces really helps advancing the research. So that’s my strategy,” he says.

Dessouky joined the faculty in the College of Engineering at UTSA in 2007, after a two-year postdoctoral stint at the University of Illinois at Urbana- Champaign, where he worked as a research scientist in the Department of Civil and Environmental Engineering.

After joining UTSA, he was provided funding to add equipment to the college’s new Superpave Facility laboratory, which was established in 2006 by Tom Papagiannakis, the chair of the Department of Civil and Environmental Engineering.

In November 2008, the American Association of State Highway and Transportation Officials (AASHTO) gave the Superpave laboratory national accreditation, enabling faculty to apply for TxDOT projects and national grants and offer asphalt binder training to workers needing certification. UTSA is one of only two universities in Texas whose asphalt laboratories have AASHTO accreditation

“Instruction takes place at the laboratory,” Papagiannakis says. “That is very important. Classes take place there, and the students gain experience working in a nationally accredited laboratory.

The laboratory allows Dessouky and his student assistants to conduct compaction testing on warm asphalt mixes, another TxDOT project that Dessouky is co-leading. Warm-mix asphalt is a breakthrough technology in the U.S. asphalt pavement industry, although it has been used in Europe for many years. The new technology allows workers in the field to heat bitumen—the viscous, black oil by-product that binds the rock material in asphalt pavement—at lower temperatures by adding liquids with a lower boiling point. Lowering the heating temperature for the bitumen saves energy and decreases the greenhouse gases emitted while paving roads.

“There is a big move for most of the state [departments of transportation] and the Federal Highway Administration to go toward that direction because of the advantage of saving energy,” Dessouky says. “We are running out of resources eventually. So this move would save millions and millions of dollars for taxpayers.”

Dessouky and his team will be testing how easily various warm mixes compact to achieve the 92 percent density standard for roads. He and his students will be making asphalt pavement samples in the Superpave laboratory—using the lab’s gyratory compactor— and testing how easily the warm mixes bind together at lower temperatures.

“If you can know how much effort you need to compact in the lab, you can estimate how many passes for the roller in the field to go over it,” Dessouky says.

His lab work doesn’t end there. While he’s working on that two-year project, he will collaborate on another yearlong project that involves traveling to TxDOT’s 25 different districts to learn how each district selects the treatment methods in its road network. They will also be gathering data about the effectiveness of each project. From these discussions, Dessouky and his team will develop a set of best practices standards for decision-makers regarding rehabilitation and preventative road maintenance. “The goal of TxDOT is to save money,” Dessouky says. “For example, if some district is using a good technique to make a good decision, and it could be cheaper, maybe other districts can use it.”

Dessouky’s projects are numerous, but he says he and Papagiannakis are expecting even more research grants now that the Superpave facility is nationally accredited

“We continuously keep an eye on what is available nationally,” Papagiannakis says.