Bridge Deck Scanning Aids Preservation, Limits Risk

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Infrasense has completed high-speed subsurface scanning on 57 bridge decks in Southwest Michigan using ground penetrating radar and infrared thermography. Infrasense engineers are currently investigating the implications this information could have on maintenance, rehabilitation, and preservation decisions.

Infrasense's vehicle-mounted GPR system

Subsurface scanning results provided more comprehensive information for making bridge deck preservation decisions.

Infrasense, Inc., has recently completed high-speed subsurface scanning surveys of 57 bridge decks in Southwest Michigan. The surveys included ground penetrating radar (GPR) using equipment manufactured by GSSI, infrared thermography (IR), and high resolution video data. GPR testing was carried out on each deck to quantify and map concrete deterioration. Mapping of surface features including patching and spalling, were included as a layer with the GPR concrete deterioration maps. Infrared IR scanning was also carried out on a select group of decks where this technology was considered appropriate.

The deck scanning results for the 57 bridge decks were utilized by NTH Consultants of Lansing, MI with the Michigan Department of Transportation (MDOT) Bridge Deck Preservation Matrix, to develop maintenance and rehabilitation recommendations for each deck. These recommendations ranged from epoxy crack sealing for the decks in good condition, to localized deck patching for those in need of minor repair, and ultimately to hydro-demolition and overlay replacement for decks in more severe condition. Replacement was recommended where further preservation was not warranted.

Traditional bridge preservation decisions are made based on the biennial routine visual bridge inspections. However, this visual inspection data does not provide the detailed subsurface condition information essential to making cost effective maintenance, rehabilitation, and preservation decisions. In reviewing the NBI data for these 57 bridge decks, Infrasense engineers investigated the implications of making decisions solely based on NBI type rating data versus decisions made using detailed subsurface data from deck scanning.

NBI data and deck scanning were compared, showing that decks classified under a single NBI rating exhibited a wide distribution deck deterioration quantities. For example, for the 32 decks with an NBI rating of "6", the deterioration percentages ranged from 0% - 27%. To quantify the implications of these differences, the Bridge Deck Preservation Matrix was used to determine which decisions would be made using NBI data only, and how these decisions would change with the use of subsurface scanning data. This analysis revealed that different decisions would be made in 30 of the 57 cases. The implications of these differences are that some decks will be under-repaired and experience accelerated reduction of service, and some will be over-repaired incurring unnecessary expense.

The results of this analysis will be included in an upcoming technical publication and available upon request at info(at)infrasense(dot)com.

About Infrasense, Inc.
Since 1987, Infrasense, Inc. has applied the most current technologies to the most difficult challenges in subsurface scanning. Infrasense’s engineers are able to nondestructively extract critical information from a diverse range of structures. The firm has conducted research to advance the field of subsurface detection, while also providing valuable information to clients across the country. Learn more about Infrasense, Inc. and its services at

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Sarah Kelly
Infrasense, Inc.
+1 (781) 648-0440
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Infrasense, Inc.

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