Bridge Inspections For A Safer Infrastructure
Field Validation Testing of Nondestructive Testing Technologies on a Concrete Bridge DeckNovember 21st, 2017 Author: Doug Thaler
After review of dozens of studies and articles we still cannot come up with one technology that matches IPC’s BridgeScan for
bridge deck and bridge approach way assessments. In order for us to get our infrastructure back on track, we need to first understand its current condition.
IPC has developed the first comprehensive bridge deck assessment and conducts these inspections within the DOT’s current maintenance budget. Many of the devices below would not be feasible just due to the fact that they are not affordable and many only look for one specific fault.
In addition, the time that they take to conduct a partial or full inspection would just keep the bridge closed for too long to be practical. With BridgeScan there are various units that can be driven from 3 miles per hour to 35mph with no lane closures. The best equipment for the job would be determined after a scope of work was provided.
BridgeScan locates delamination, debonding, voids, water intrusion, gravel compactness, rebar placement and more. The shown device can penetrate 15 feet into the ground and will completely map a bridge deck in no time. It goes beyond conventional ground penetrating radar (GPR) and can provide quantitative data to the department of transportation to be used in budgeting future maintenance and repairs.
Lets take a closer look at some of these other technologies.
“In November of 2010 as part of a SHRP2 research project was conducted By Rutgers University with the University of Texas El Paso to validate various NDT technologies on a concrete bridge deck. The concrete bridge deck was in Haymarket, Virginia and the videos were pulled from and are archived from the TRB’s SHRP2 site. Teams from industry and academia demonstrated how their NDT technologies—such as ground penetrating radar, impact echo, and infrared thermography—can be used to detect deterioration in concrete bridge decks. Video segments of the rodeo are include.
The technologies are also being validated to develop an electronic library of NDT technology resources for practitioners.
Haymarket Bridge underwent extensive preliminary evaluation as a part of the LTBP Program’s Pilot project, using both destructive and nondestructive means, visual inspection, and full-scale loading.
The electrical resistivity method measures the concrete’s ability to support ionic flow by measuring the concrete resistance. In many cases the measured resistance can be related to the corrosion rate.
Galvanostatic Pulse Measurement
In the galvanostatic pulse measurement method, an anodic current pulse is galvanostically induced into concrete from a counter electrode that is placed on the surface together with a reference electrode. This method is designed to estimate the corrosion rate of concrete by measuring the potential variation, electrical resistance, and polarization.
Ground Penetrating Radar
Ground penetrating radar is an electromagnetic method that produces graphic images of subsurface as a result of reflection of electromagnetic waves from material interfaces. It can detect deterioration in concrete, signs of corrosive environment, delamination, voids, anomalies in concrete, water-filled or epoxy-injected cracks, and debonded overlays.
The half-cell potential measurement is used to evaluate the activity of corrosion processes in steel-reinforced and prestressed concrete structures. In this method, a reference electrode is placed on the surface. When the electrode is shifted along a line or grid on the surface of a concrete surface, the spatial distribution of corrosion potential can be mapped.
The impact echo method is a frequency response technique used to detect and assess delamination, evaluate vertical cracks and materials, and characterize grouting conditions in tendon ducts.
Impulse Response In impulse-response NDT, a stress pulse is generated by a mechanical impact on the surface of the tested object and the response of the object recorded using a nearby receiver. To learn about the condition of the object, both the impact and response functions are transformed into the frequency domain to obtain impedance functions or mobility spectra.
Infrared (IR) thermography is used to detect concrete defects, such as delaminations, debonding, and concrete disintegration. IR thermography can quantify these defects by measuring the surface temperature influenced by the changes in subsurface material density, heat capacity, and heat conductivity changes.
Echo The ultrasonic pulse echo technique method uses high-frequency transducers to create and detect arrivals of ultrasonic pulses. The time it takes to travel to another point is measured. This method can be used to detect voids, grouting conditions in ducts, material degradation or changes, and other anomalies. It can also be used to localize rebars and tendon ducts.
MIRA System-University of Texas at El Paso
Ultrasonic Surface Waves.
The ultrasonic surface waves (USW) method involves measurement of the surface wave velocity to obtain material modulus, as a sign of possible degradation of material properties, or detect possible defects, like vertical cracks or delaminations. Waves generated by an impact of an electromagnetic or mechanical source are being recorded by a pair or several receivers to enable calculation of the surface wave velocity.”
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