GPR Leads the Way for DOT Highway Inspection
The average driver can usually see when pavement deterioration becomes problematic—there will be tearing or rutting on the surface of the road or cracking in wheel paths that decreases safety on the roadway. Underneath the surface of the pavement, however, the signs of deterioration existed long before they were visible and experienced by drivers. Delamination between asphalt layers underneath the surface of pavement is often due to layer debonding or stripping, which typically is not visible, especially in the early stages. Additionally, manual destructive methods for evaluating pavement problems can be time consuming and expensive for state DOTs and other transportation agencies.

State DOTs, however, have found ways to address these challenges through advanced technologies out of the second Strategic Highway Research Program (SHRP2), a partnership between the Federal Highway Administration, the American Association of State Highway and Transportation Officials and the Transportation Research Board. SHRP2 solutions are a comprehensive and data-driven set of products, procedures and best practices meant to help transportation agencies save time, money and lives through innovative solutions to common transportation challenges. One solution—Advanced Methods to Identify Pavement Delamination (commonly referred to as R06D)—features two nondestructive testing (NDT) technology systems that can spot problems in the asphalt pavement beneath the surface in a safer, faster, and less expensive way than previously done.

"Right now for state designers, the way to truly evaluate pavement is taking cores," Stephen Cooper SHRP2 renewal pavements engineer and FHWA product lead for R06D says. "It’s a very slow process, and a destructive one. You’re also impacting the traveling public. The great thing about these SHRP2 NDT technologies is that they provide DOTs with information right away so they can identify those problem areas in advance so that we can then do some further examination and address the issues."

Six state DOTs tested the NDT technologies included in R06D through the SHRP2 Implementation Assistance Program (IAP), which provided financial assistance and technical guidance from subject matter experts.

GPR Leads the Way

One technology included in R06D is 3D ground penetrating radar (or 3D-GPR). The 3D-GPR technology can detect certain delamination issues, using an antenna array with a frequency sweep that can be operated at highway speeds (over 60 miles per hour). The wide antenna array reduces the number of passes required to cover the lane width, allowing operators to cover larger areas at a time. The technology can also be used to gather other subsurface information, such as the location of utilities. Since the technology can be used at highway speeds, DOTs can utilize the technology in live traffic, eliminating the need for closures—a real benefit to drivers.

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