Various methods exist to identify distresses in concrete and asphalt concrete overlaid pavement, and simple patching is usually a good temporary fix. But less-experienced engineers may miss the signs of early serious structural damage to the pavement because of a lack of experience or a decision-making process based only on visual distress surveys.

“By the time a visual inspection shows distress, it’s time for a major overhaul,” says Texas Transportation Institute’s (TTI‘s) Tom Freeman, engineering research associate. “In this project, we collected the last 30 years of field experience and developed tools that engineers can fit in their pockets.”

The research team developed a pocket field manual, a field survey and field guidelines. As engineers retire from TxDOT, too often their expertise goes with them. Freeman’s work has captured some of that corporate knowledge, making the maintenance process more efficient overall.

The field manual provides a standard for maintenance crews to use in determining and describing the problems they may encounter; it also includes pictures, possible causes and recommended lab tests. The team also used a survey to evaluate the effectiveness of full-depth repair, various joint repair techniques, joint resealing and dowel bar retrofit with diamond grinding.

The guidelines include non-destructive test procedures for subsurface layers, such as the falling weight deflectometer and ground penetrating radar (a technique developed at TTI). The guidelines also provide discussion on each maintenance stage, promoting the best standard practices and specifications used by state departments of transportation across the country. A step-by-step repair method and decision-making process gives engineers the options of preventative maintenance, functional or structural concrete pavement repair or full resurfacing.

“Routine maintenance at the right time can extend pavement life in a cost-effective manner,” says Freeman. “It takes longer to repair a section of very poor pavement, while with the same amount of resources, an agency can maintain far more sections of pavement in good and fair condition.”

These tools are timely since there is a renewed federal interest in improving transportation infrastructure, which is good news to state departments of transportation. Freeman’s next project will work with TxDOT to develop a class that will teach engineers around the state the decision-making processes found in these products.

“This research defines another set of tools for TxDOT engineers to economically maintain pavements on an aging transportation system with decreasing funding,” says TxDOT‘s Paul Montgomery, director of maintenance. “These tools help us along the path of progress in pavement management.”

The pocket field manual, field survey and field guidelines developed by TTI researchers will aid maintenance crews in identifying concrete distresses like the ones shown above.

A recently completed research project, sponsored by TxDOT and conducted by the Texas Transportation Institute (TTI), examined methods for improving the safety and durability of seal-coated roadways. The project developed guidelines for how and when to vary the amount of asphalt being applied across the width of a pavement.

“A roadway does not wear evenly across the surface because traffic is usually channelized,” says Paul Krugler, research engineer with TTI. “The difference in surface texture may result in new seal-coat aggregate not bonding adequately outside of the roadway wheel paths, or the asphalt may rise to the surface in the wheel paths. Either situation diminishes roadway quality, and the loss of skid resistance in the wheel paths can be a safety issue. Asphalt rising to the surface in the wheel paths is commonly known as flushing, and it’s what we’re trying to prevent by varying the amount of asphalt sprayed on the roadway.”

Transversely varying asphalt rates (TVAR) works by designing the asphalt shot rate specifically for the wheel path conditions. If the wheel paths are worn down or exhibiting flushing, the proper asphalt rate is somewhat lower. Then, the asphalt shot rate is increased for the areas outside of the wheel paths. Additional asphalt is needed there to fill the greater surface texture and still have adequate asphalt available to ensure proper bonding of the aggregate. The goal of TVAR is an even coating of aggregate that is well-bonded across the entire width of the roadway but without causing flushing. This bonding optimizes skid resistance and makes the roadway safer.

Last summer, researchers interviewed TxDOT maintenance personnel throughout the state to gather information on how often and what criteria they used to set these transversely varied asphalt rates. The result of the project was a comprehensive guidebook with step-by-step instructions on the TVAR process. For the implementation phase of the project, the research team is hitting the road this spring, teaching five workshops on TVAR.

In addition, roadways that underwent TVAR seal coats last year will be evaluated in the future for effectiveness in eliminating reoccurring flushing. “We can adjust the numbers in our guidebook if necessary,” says Krugler.

“The whole concept of TVARs is to put more asphalt on the road,” says Paul Montgomery, who served as the project director and is the TxDOT director of maintenance for the Lufkin District. “We want more asphalt on the road, but we don’t want to get flushing in the wheel paths when we do it. By using the set of guidelines developed by TTI, our construction inspectors and maintenance crews can achieve this goal and optimize our seal-coat applications, while also making the roadways safer for the traveling public.”