The purpose of this study was to evaluate the reproducibility and accuracy of Ground Penetrating Radar (GPR) in locating delaminations and de-bonding in asphalt concrete overlaid concrete bridge decks. The traditional "chaining" method is a less effective option for finding subsurface defects after an overlay is in place. An infrared thermographic and GPR evaluation was conducted on the I-70 Polk-Quincy viaduct in 1993. A second GPR study was performed in 1997 to evaluate the condition of the bridge deck previous to removal of the existing asphalt overlay and high density concrete overlay and repair of the deteriorated deck. The results of the 1997 GPR study were compared to the results of the 1993 GPR study, the 1998 through 1999 chaining, actual repair areas and portions of the 1989 Geotechnical Unit bridge deck evaluation.

Reinforcement concrete (RC) bridge decks are surveyed regularly to ensure that they are safe to use and to determine if they require rehabilitation or replacement. The bridge surveys include evaluating subsurface bridge condition. RC bridges have steel reinforcement bars, also called rebars, embedded in their surface, which are prone to corrosion due to factors like moisture, carbonation, use of deicing salts and aging. By the time the effect of corroded rebars is visible on deck surface in form of cracks, the damage is tremendous. If left unchecked, corroded rebars can deteriorate at a faster and significantly affect bridge integrity. So, it is very important to timely identify and repair deteriorated rebars. Ground Penetrating Radar (GPR) is a widely used non-destructive technology (NDT) for detecting subsurface anomalies in variety of structures including RC bridges. The raw GPR data is represented as images that can be processed for obtaining a deterioration map of a bridge, which indicates the level of corrosion in rebars for the entire bridge. The existing methods to generate the deterioration map using GPR data are semi-automated, time consuming and depends on expertise of the engineer analyzing the data. In this thesis, we work towards automating the process of obtaining deterioration map of RC bridge decks based on measuring signal attenuation at the upper rebar mat using GPR. Intensity and gradient-based feature vectors were explored to construct a classifier, which can detect the regions of interest (ROI) corresponding to each rebar in images. Each classifier was tested on datasets constructed from two different bridges. Further, the exact location of rebar was found in each ROI. Once all the rebars were detected throughout the bridge, depth-correction of the measured attenuation is applied so that the component of that measured attenuation caused solely by variation in rebar depth does not skew the results. Finally, a deterioration map was generated which indicates the level of corrosion in the bridge. The proposed algorithm was tested on two RC bridges and the deteriorated regions obtained are compared with the results obtained using existing tools.

"Ground penetrating radar (GPR) data were acquired across four bridge decks with the objective of developing an advanced workflow for GPR operation that would allow the bridge owners to estimate repair quantities for certain bridge decks, based on GPR data. The primary contributions from this research are as follows: 1. It was demonstrated that the conditions of bridge decks can be cost-effectively and efficiently assessed using the GPR tool. 2. The GPR tool's ability to provide rapid and reliable results in comparison with conventional bridge deck condition assessment techniques was established. 3. The qualitative and quantitative relationships between the GPR reflection amplitude and depth of concrete degradation were analyzed to develop an effective technique to estimate the amount of deteriorated concrete present in a particular bridge deck; this technique could enable bridge owners to use the GPR tool (only) to estimate the thickness of concrete that would be removed by processes such as hydro demolition. 4. The air-launched and ground-coupled GPR systems were compared in terms of accuracy of data acquisition and reliability of results. It was determined that air-launched GPR is a reliable tool for the fast and cost-effective assessment of bridge decks. This work is new and important because it extends the traditional use of the GPR technique and presents the advanced approach for data interpretation and concrete material removal estimation, especially in areas where deterioration was not visually exposed"--Abstract, page iii.

This report from the second Strategic Highway Research Program (SHRP 2), which is administered by the Transportation Research Board of the National Academies, describes development of nondestructive testing techniques that are capable of detecting and quantifying delaminations in HMA pavements. This NDT technique is applicable to construction, project design, and network-level assessments. This e-book contains 5 different volumes, the last 4 involving more technical descriptions of the project.

There is an urgent need for methods that can be used to rapidly and nondestructively determine the condition of an old concrete deck beneath an asphaltic concrete wearing course. In recognition of this need, the technique of ground-penetrating radar was investigated. In practice, microwave-frequency impulses of about 1.1 nanosecond pulse width are transmitted into an overlaid bridge deck by a radar transducer that also serves as a receiver. When these electromagnetic pulses are directed through a delaminated concrete area, there is some pulse reflection from the deteriorated concrete, (the more severe the delamination, the more pronounced the reflection), in addition to the normal reflections at the air-asphaltic concrete and asphaltic concrete portland cement concrete interfaces and the reinforcing steel. The reflected pulses are then picked up by the transducer and transformed into the audio frequency range by a time-domain sampling technique and displayed on a facsimile graphic recorder as a pulse reflection profile. Although intended for use on overlaid bridge decks, the technique was experimentally used on three non-overlaid concrete decks and two old concrete deck slabs, in addition to three overlaid decks. To obtain 'ground truths' for comparison, conventional soundings were performed on the non-overlaid decks and slabs and two of the overlaid decks after their overlayments were removed. The results showed that ground-penetrating radar can be used successfully to detect concrete delaminations in both nonoverlaid and overlaid bridge decks, since the delaminations are manifested in the recorded radar pulse reflection profiles as recognizable irregularities in the reflection bands corresponding to the top mat of the reinforcement. These irregularities, or signatures of concrete delaminations, were often in the form of depressions, but in some instances appeared as blurs or breaks in the profiles. It was also found that the radar sometimes missed small delaminated areas of about 1 ft. (0.3 m) width and less. However, this relatively small deficiency does not impair the overall effectiveness of the technique as a nondestructive inspection tool for both types of decks. The experimental procedure can be used as is to inspect decks, if lane closure is not a major concern. However, with little further experimentation, this requirement may be completely eliminated.

The state of Wyoming alone has 13.1 million square feet of bridge deck, and evaluation of those decks has become an important part of the Wyoming Department of Transportation's (WYDOT) management of bridge repairs. The authors believe that development and advancement of nondestructive evaluation methods over the past 25 years may provide a more efficient, standardized, and accurate method for evaluating bridge deck conditions compared with current practices. A study was performed on three bridge decks in Wyoming: the First Street Bridge in Casper, the Douglas I-25 Bridge, and the Remount I-80 Bridge. For each bridge, an investigation was done using standard WYDOT practices for chain dragging. In addition, the bridges were evaluated using impact echo, thermal imaging, and ground-penetrating radar (GPR) techniques. All three methods considered were successful, and the damage locations between the impact echo, thermal imaging, and GPR generally correlated well. Based on this study, a complete bridge deck evaluation should combine impact echo with GPR testing to provide the most accurate predictions of delamination and debonding in support of optimal maintenance decisions.

The ASCE report card 2013 rated bridges at a grade of C+, implying their condition is moderate and require immediate attention. Moreover, the Federal Highway Administration reported that it is required to invest more than $20.5 billion each year to eliminate the bridge deficient backlog by 2028. In Canada 2012, more than 50% of bridges fall under fair, poor, and very poor categories, where more than $90 billion are required to replace these bridges. Therefore, government agencies should have an accurate way to inspect and assess the corrosiveness of the bridges under their management. Numerical Amplitude method is one of the most common used methods to interpret Ground Penetrating Radar (GPR) outputs, yet it does not have a fixed and informative numerical scale that is capable of accurately interpreting the condition of bridge decks. To overcome such problem, the present research aims at developing a numerical GPR-based scale with three thresholds and build deterioration models to assess the corrosiveness of bridge decks. Data, for more than 60 different bridge decks, were collected from previous research works and from surveys of bridge decks using a ground-coupled antenna with the frequency of 1.5 GHz. The amplitude values of top reinforcing rebars of each bridge deck were classified into four categories using k-means clustering technique. Statistical analysis was performed on the collected data to check the best-fit probability distribution and to choose the most appropriate parameters that affect thresholds of different categories of corrosion and deterioration. Monte-Carlo simulation technique was used to validate the value of these thresholds. Moreover, a sensitivity analysis was performed to realize the effect of changing the thresholds on the areas of corrosion. The final result of this research is a four-category GPR scale with numerical thresholds that can assess the corrosiveness of bridge decks. The developed scale has been validated using a case study on a newly constructed bridge deck and also by comparing maps created using the developed scale and other methods. The comparison shows sound and promising results that advance the state of the art of GPR output interpretation and analysis. In addition, deterioration models and curves have been developed using Weibull Distribution based on GPR outputs and corrosion areas. The developed new GPR scale and deterioration models will help the decision makers to assess accurately and objectively the corrosiveness of bridge decks. Hence, they will be able to take the right intervention decision for managing these decks.

This report summarizes efforts initiated and sponsored by the New Hampshire Department of Transportation related to location-specific predictions of corrosion and freeze/thaw induced deterioration on existing bridge decks scheduled for rehabilitation. In 1998, twin 842-ft (257-m) interstate bridges spanning the Connecticut River between Lebanon, New Hampshire and White River Junction, Vermont were surveyed using a combination of horn and ground-coupled antennas. These surveys, supplemented by an underside inspection and limited coring and chloride testing, were successfully used to estimate and locate repair areas prior to a deck rehabilitation project on the structures. In 1999, four structures located along I93 in Thornton-Woodstock, New Hampshire were surveyed without the use of supplemental, destructive testing or lane closures. Contour maps were produced on all structures, showing varying degrees of predicted deterioration.

The Penetradar Integrated Radar Inspection System (IRIS) Ground Penetrating Radar (GPR) was selected by Dalhousie University DalTech as the most appropriate technology for assessing the condition of reinforced concrete bridge decks because of the ability of the system to penetrate through asphalt concrete overlays and Perform data collection at traffic speeds up to 75-80 km/hr. A collaborative research program was designed by Dalhousie University DalTech and the Nova Scotia Department of Transportation and Public Works to examine the accuracy and confidence with which GPR can be used to predict the quantity and location of laminations and concrete scaling On asphalt covered bridge decks. Seventy-two bridge decks were surveyed at traffic speeds using GPR for deterioration estimation. The GPR data was processed manually to determine areas of excess signal attenuation and areas of high concrete relative dielectric constant. Deterioration predictions made using GPR were also compared quantitatively and spatially to ground-truthing data obtained from nine bridge decks using the well-established chain drag and half-cell potential surveys after the asphalt was removed from each bridge deck just prior to repair.