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Development of the Total Pavement Acceptance Device (TPAD) and Initial Pavement Studies

TPAD Rolls into the Future of Road Maintenance

What Was the Need?

To keep pavements in the best shape possible, TxDOT needs to periodically determine their true condition—including underneath the pavement surface. Testing pavements is a painstaking process that often requires boring holes into pavement, in a process called coring. Each core sample is indicative of the conditions at that particular spot—but an effective evaluation of pavement requires a continuous assessment of a road. While pavement deflection testing, which skips the coring step, has been around for about 20 years, there wasn’t an efficient way to continuously determine a road’s overall condition. To effectively analyze road failures, TxDOT needed a comprehensive device that simultaneously collected data from multiple non-coring testing methods while moving at a higher speed than possible with existing testing devices.

What's the Solution?

As part of a TxDOT-funded project years ago, CTR developed a piece of equipment that can conduct certain pavement tests without coring and while moving along the road (called a rolling dynamic deflectometer, or RDD). However, researchers found that the RDD results were more effectively used when combined with data from other testing methods, such as pavement layer thicknesses and subsurface conditions from ground-penetrating radar (GPR), pavement right-of-way and surface conditions from a video camera, pavement surface temperatures, and precise distance measurements. So a new, multifunction pavement testing device was developed through a joint effort between TxDOT, CTR, and the Texas A&M Transportation Institute at Texas A&M University (TTI). This device is called the total pavement acceptance device, or TPAD. Combining multiple testing methods into a single machine produces maintenance and rehabilitation data that is far more comprehensive and useful than using the individual devices separately.

How the TPAD Work: The testers drive the TPAD along a section of highway at 2 to 3 miles per hour. RDD and GPR data are recorded along with video information and global positioning coordinates. If any questionable areas are spotted during data analysis, the testers can check the video to see if anything is visible on the surface. Additionally, the global positioning system marks each location with extreme accuracy. If a road crew needs to visit the site to access it in person, they know exactly where to look.

Research Benefits

The TPAD not only gathers multiple types of data at once, but also doubles the speed of the RDD: 2 mph versus 1 mph. The multi-functions of the TPAD enable a robust evaluation of the pavement conditions in a single pass in a relatively short time. TPAD technology has opened a new door in road surface maintenance and rehabilitation. Engineers are now able to thoroughly evaluate the structure of a road and recommend short-term and long-term maintenance to prolong its life. Joe Leidy, a Pavement Structural Engineer for the TxDOT Austin District, is a TPAD advocate. “Ultimately, we should see a savings of taxpayer dollars by making better decisions with our rehabilitation strategies,” the said.

Project Number

0-6005

Status

Completed

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