Infrasense, Inc., a national leader in ground penetrating radar and infrared thermography bridge deck surveys, has begun a busy data collection season, with many nondestructive testing projects scheduled across the United States. In total, Infrasense plans to scan nearly 350 bridge decks this spring and early summer, with projects ranging from Connecticut to Montana. Infrasense also has upcoming pavement structure evaluation projects across the U.S. GPR pavement applications include subsurface void and moisture detection, layer thicknesses, and density of new HMA pavements.
Infrasense has played a key role in the development and implementation of GPR, Infrared Thermography, and other NDT methods for evaluating transportation infrastructure over the past 27 years. One of the most common applications of the ground penetrating radar technology is the determination of pavement structure layer thicknesses. Unlike traditional coring, GPR requires no lane closures and provides a timely and cost-effective means of obtaining continuous thickness data. This data is accurate, (within 10% of core values), and may be used for network-level pavement management or project-level rehabilitation design, and provides the necessary information in FWD analyses to calculate the remaining lifespan of an existing pavement. GPR data also reveals patterns and anomalies in pavement structure that often go unnoticed using traditional coring techniques.
Infrasense surveys have covered over thousands of lane miles of pavement. Projects range in size from a few miles in length, to over 1,500 lane miles of county roads in North Dakota working with the North Dakota State University's Upper Great Plains Transportation Institute.http://www.ugpti.org/downloads/road_needs/testing.php
Nondestructive scanning data is also collected on bridge decks. Ground Penetrating Radar data is used to identify corrosion induced delamination, and to estimate rebar depth. Decks in good condition consist of strong and uniform radar reflections from the rebar, whereas weak and inconsistent reflections indicate rebar-level bridge deck deterioration.
Infrared Thermography data is collected to directly identify and locate delaminations in the concrete at the reinforcing steel. Infrared data is collected in a series of passes across each deck, with each pass covering a deck width of between 12 and 15 feet. The survey produces a series of infrared images collected every foot of vehicle travel. During the survey, delaminations that heat unevenly due to thin voids at the reinforcing steel appear in the IR image as brighter "hotspots". Because many of these decks have overlays, the reinforcing can be 4-5 inches from the surface, and sounding is not always capable of detecting delamination at this depth. Deck surface conditions, such as patching and spalling, are mapped and quantified using a high-resolution video system operated concurrently with the infrared survey.