GPR as a Tool for Pavement Condition Assessments and Bridge Deck Analysis

Over the past 20 years, Ground Penetrating Radar (GPR) has become a tool routinely used by engineers, contractors and asset managers in the fields of subsurface utility engineering (SUE), utility verification and structural evaluations.

Bhate Geosciences (BHATE) was among the first in the southeast to utilize GPR.  Now having multiple teams solely dedicated to utilizing the technology, BHATE has cost-effectively provided these services on some of the largest projects in the region.

“The importance of having personnel dedicated to utilizing GPR cannot be stressed enough. Correctly interpreting GPR data is key to getting accurate and repeatable results from a geophysical survey.” – Bhate GPR Geophysicist, Jack Morrisroe.

Mirroring developments in computer technology, GPR manufacturers have been able to develop systems that are able to operate at faster speeds, storing more data and with increased data clarity. Technological advancements such as this are what have now enable air-launched traffic-speed GPR to provide valuable information on both pavements and bridges.

With antennas suspended 20 inches above the pavement surface, air-launched GPR is capable of collecting information about pavement layers and subsurface anomalies at traffic speeds as high as 60 miles per hour.

One particular project where traditional coring provided thickness information that was not representative of the pavement overall was in the Florida Panhandle.

“Bhate Geosciences recently conducted a pavement thickness evaluation for us. We were impressed with the data delivered to us and with the speed at which the data was collected. The technology they used enabled us to understand the nature of the pavement in a way that traditional coring would not have been able to and we recognize opportunities for routine implementation of GPR technology in the future” – Escambia County, Florida.

GPR can provide information that can be used for:

• Routine maintenance such as overlays
• QA/QC of new pavement thicknesses
• Understanding unrecorded maintenance prior to milling
• Increased accuracy of back calculation of FWD data
• Asphalt deterioration including stripping and moisture filled de-bonding
• Subsurface anomalies such as voids
• Understanding pavement thickness variations across the profile of a lane

DOTs and other groups have researched the accuracy of GPR for the measurement of pavement layers. Typical findings show an accuracy of between 2% and 10% of thicknesses derived from coring, with the larger difference typically from aging and deteriorated pavements.

A reduction in coring results in less exposure to traffic for work crews and a significant reduction in disruption to road users and costs from lane closures. One significant area that GPR is removing workers from harm’s way is during bridge deck deterioration inspections.

A correlation exists between areas of concrete exhibiting corrosion or delamination and that of attenuated signal strength from GPR reflections. This enables air-launched GPR to both map the location and severity of deterioration, in addition to estimating percentages of deteriorated concrete.

Traditional bridge and parking deck inspections for delamination have involved hammer sounding or chain dragging. Not only is GPR both faster and less subjective than traditional methods, but it also can identify corroded areas not yet exhibiting delamination. This information can be valuable to a structural engineer for both monitoring deterioration and estimating repair quantities. Whether a parking deck or a bridge deck, GPR can be used as a rapid and cost-effective tool to understand existing conditions and plan rehabilitation.

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