FHWA NDE Center RESEARCH & DEVELOPMENT
The Problem of Deteriorating Bridge Decks
Increases in traffic volume and aging infrastructure mean that the management of bridges is currently very important. To address the need for quantitative information on the condition of bridges the Federal Highway Administration (FHWA) is
pursuing a program of research and development of non-destructive evaluation methods. One aspect of this work is the investigation of bridge deck integrity.
The service life of the bridge deck is much shorter than the bridge substructure and superstructure. The deck may require replacement every 15 to 20 years while most other components last 40 years or more. Bridge decks may become structurally deficient due to corrosion of reinforcing steel that leads to delaminations and spalling. The ability to detect these defects is critical in directing repairs
to the most at risk bridges and thus has great implications on the optimum use of limited funds. In addition to locating defects, information on the internal structure such as thickness of concrete and position of steel reinforcement may be required for evaluation of the bridge.
Delamination caused by the corrosion of reinforcement is an important problem influencing the structural integrity of highway bridge decks.
Water and oxygen exist in the pore space of concrete, with the ingress of chloride ions, or carbon dioxide, corrosive conditions are formed
to produce rust on the surface of the steel. This product of corrosion takes up a greater volume than the original steel and eventually leads
to debonding of concrete from the steel. Typically these localized debonded areas join to form delaminations through the bridge deck
at the level of the reinforcing mesh. Growth of the delamination may be exaggerated by freeze-thaw action.
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| Delaminated bridge deck section. |
Bridges are critical components in the flow of traffic and the costs of closure may often be prohibitively high. A deck inspection tool which is able to operate along with the traffic flow is necessary to avoid disruption. The HERMES Bridge Inspector (High-speed Electromagnetic Roadway Mapping and Evaluation System) is designed to meet this need. The system has been constructed to scan bridge decks at highway speeds and produce images of the deck interior.
However, when data is collected at highway speeds, as the HERMES is designed to do, it is not possible to repeat measurements at the same location to reduce noise by averaging. A radar system which slowly scans over the surface of the pavement has therefore been developed which produces high quality images from averaged scans. This system is meant for imaging areas of special interest and would require lane closures on the bridge due to the slow rate of data collection. This radar device is named PERES (Precision Electromagnetic Roadway Evaluation System).
For More Information, please contact either by e-mail or telephone:
Dr. Mike Scott (202) 493-3124
Dr. Ali Rezaizadeh (202) 493-3119
Advanced Ground-Penetrating Radar Inspection of Bridge Decks
The HERMES Bridge Inspector
The PERES Bridge Inspector
Current Work on Hermes II
