Maintenance of the nation’s infrastructure is a growing concern. No one wants to be delayed by road closures due to emergency repair. Unfortunately, often the organizations responsible for repairing and maintaining our roads are unaware of areas in the roads that need repair until the road is so damaged that it requires emergency repair. In the case of sensitive road areas like bridges – where a failure can lead to costly repairs and potential injury to motorists – there a better way. Ground penetrating radar (GPR) is one of the best and most reliable non-invasive methods of performing bridge deck inspections.
A Better Way to Perform Bridge Deck Inspections
Visual inspections are helpful, but GPR allows the technician and engineers to see what is happening below the asphalt. Using analysis and data, ground penetrating radar can uncover unseen problems and the extent of problems that can be seen with a visual inspection.
GPR Won’t Disrupt Traffic
Invasive methods of bridge deck inspections are often excellent, but they involve lane closures and traffic redirection at the very least, often for several days or weeks. Why disrupt traffic for an extended period of time only to find out that the structure is solid and needs no repair? A GPR scan during a bridge deck inspection will typically require less time and require little to no traffic disruption. This data can then be confirmed with a visual inspection during the repair.
GPR is Simple to Use, but Advanced Enough to Provide Excellent Data
Many non-invasive methods of bridge deck inspection involve complex interpretation of data, but GPR provides a fairly simple graphic display of the deck and its reinforcement, up to several feet deep. In addition, the GPR can collect data files which can be analyzed using software suited to this purpose, to confirm visual data.
Rebar Corrosion And Migration
In most cases, pouring concrete over steel reinforcement provides a natural protection against corrosion of the reinforcement, since chemicals in the concrete react with the outer surface of the reinforcement to provide an effective barrier against corrosion. Unfortunately, when de-icing salts are applied to the surface of the deck, often chloride or sulfate ions from action of melting the ice will migrate into the concrete and, over time, wear away this layer of protection, resulting in corroded reinforcement. This occurs due to the uneven distribution of the salts, turning the upper portion of reinforcement into anodes, and the reinforcement below into a cathode, which speeds the corrosion process.
Rebar migration, or “creep”, occurs when the structural integrity of the bridge deck has deteriorated to the point that the reinforcement is pushed away from its original position by internal settling and pressure from within the structure. Both corrosion and creep can have deleterious effects on the viability of the bridge structure, and both are detectable by Ground-Penetrating Radar.
GPR will show visually if any rebar has migrated (if it falls outside the normal pattern) or corroded (especially if it has corroded completely). Further investigation using deterioration mapping software can uncover more of these reinforcement flaws. Ground-coupled GPR (as opposed to air-coupled GPR, usually mounted on a moving motor vehicle) has specific advantages, in that it has a higher-resolution output, and is not as easily affected by ambient radio signals.
Concrete Cracking And Delamination
Cracking and delamination in concrete occur during a variety of stages in the life of a bridge. Improper concrete mixes and pouring techniques can lead to cracking and delamination, but these defects in the concrete can also occur over time due to freezing and thawing cycles and other environmental factors. Ground-coupled GPR, in concert with deterioration mapping software, is an excellent tool to measure concrete cracking and delamination, as well as thickness of the deck. It can also be used to measure the effectiveness of previous repairs using epoxies, and can often detect the presence of concrete with a high concentration of chloride ions because of the changes in electrical potential in these areas. For an excellent overview of the benefit of GPR for bridge deck inspection, please see the Iowa DOT’s report on non-destructive testing methods.
GPR for the Best Results
Ground-penetrating radar is an exceptional method for scanning bridge decks because it is reliable, relatively inexpensive, non-invasive, and flexible for your needs. Encompass Inspections are experts in the field of GPR scanning, and we are here to help. Visit our website or contact us to find out more.