Using GPR to Measure Pavement Conditions

The American Society of Civil Engineers (ASCE) gave America’s roadways a “D” on  its 2017 Infrastructure Report Card, same as 2013, but slightly better than the “D-” in 2009. The report describes our roadways as “crowded, frequently in poor condition, chronically underfunded, and becoming more dangerous.”  ASCE says one in five miles of highway pavement is in poor condition and there is an increasing backlog of rehabilitation needs.

But how can you rehabilitate what you cannot effectively measure? Knowledge of the infrastructure’s condition is critical to developing a reliable, cost-effective pavement management plan. Collecting accurate data is essential since any decision made about rehabilitation alternatives depends on the integrity of the data assembled.

The first step in the performance assessment process is developing an inventory of the infrastructure’s condition. One of the most accurate methods to determine the condition is ground penetrating radar (GPR) technology. GPR is a geophysical method that uses radar pulses to image the subsurface to measure the structure’s thickness and identify cracks, voids and areas of deterioration. This non-destructive testing method provides faster and more thorough results than traditional pavement coring methods. Trained engineers can interpret GPR scans and map out areas that require immediate attention and those that need a long-term repair plan.

The most advanced GPR technology for infrastructure asset management is a vehicle-mounted air-launched system. With antennas suspended 20 inches above the pavement, air-launched GPR can collect information about pavement layers and subsurface anomalies at traffic speeds up to 65 miles per hour. An additional benefit of this method is there is no disruption to road users and the GPR-mounted vehicle can drive alongside traffic without interruptions.  This significantly improves safety during road work construction, which typically requires blocking lanes for personnel working with manual equipment.

GPR technology can provide roadway information that can be used for:

• Routine maintenance such as overlays
• Quality assurance/quality control for new pavements
• Gathering data on unrecorded maintenance prior to milling
• Increased accuracy of back-calculation of falling weight deflectometer (FWD) data
• Determination of pavement deterioration including stripping and moisture-filled de-bonding
• Understanding pavement thickness changes across the profile of a lane

GPR can help predict where a sinkhole might happen. It can be used to identify subsurface anomalies where voiding is potentially occurring.  This data can identify areas that need to be addressed to prevent potentially serious problems in a timely and cost-effective manner.

Air-launched GPR can also be used in bridge deck evaluations.  Bridges scored a “C+” on the ASCE’s Infrastructure Report Card  because 40 percent of the nation’s bridges being 50 years or older and almost 10 percent of bridges are considered structurally deficient. With estimated rehabilitation costs totaling over $120 billion, efficient bridge evaluations and strategic repairs are necessary to maximize rehabilitation efforts.  The air-launched GPR evaluations can provide bridge engineers with areas of fracturing, rebar corrosion, trapped moisture content and rates of deterioration.

While there will never be enough funding to solve all our infrastructure needs, we all share a role in renewing the nation’s infrastructure. Solving these problems will take collective action. Every day we delay investing in and effectively improving our nation’s infrastructure, we escalate our costs and risk our safety.

Interested in BHATE’s GPR services? Contact us now for more info on our GPR services or a quote.