Concrete corrosion induced by deicing agents can decrease the durability of concrete bridge decks by causing cross-sectional loss of reinforcement, concrete delamination, and spalling owing to the expansion of corroded reinforcement. The installation of overlays can extend the service life of the deteriorated decks. However, overlays present challenges in the evaluation of the corrosion condition of the underlying decks. This laboratory study employed three nondestructive testing (NDT) methods to assess the effects of seven types of overlays on corrosion evaluation for concrete bridge decks. The NDT methods were electrical resistivity (ER), ground-penetrating radar (GPR), and half-cell potential (HCP). The ER method could not evaluate the corrosive environment in the concrete decks through the overlays. The GPR method could detect the corrosive environment through four of the seven overlays. The HCP method could detect the decrease of electrical potential over the actively corroded reinforcement for all seven specimens; however, only two of the seven specimens could be identified as having active corrosion per ASTM C876-15, Standard Test Method for Corrosion Potentials of Uncoated Reinforcing Steel in Concrete . Overlay debonding did not affect GPR and HCP testing results in this study.

" TRB's second Strategic Highway Research Program (SHRP 2) Report S2-R06A-RR-1: Nondestructive Testing to Identify Concrete Bridge Deck Deterioration identifies nondestructive testing technologies for detecting and characterizing common forms of deterioration in concrete bridge decks.The report also documents the validation of promising technologies, and grades and ranks the technologies based on results of the validations.The main product of this project will be an electronic repository for practitioners, known as the NDToolbox, which will provide information regarding recommended technologies for the detection of a particular deterioration. " -- publisher's description.

Concrete bridge deck overlays have been used in the United States since 1960 to extend the service life of deteriorated concrete bridge decks and improve reliability. Concrete bridge decks with overlays suffer various types of deterioration, so it is necessary to identify and assess the effectiveness of different nondestructive evaluation (NDE) technologies in the laboratory under controlled conditions and in the field under actual conditions. This report provides an overview of seven types of widely used overlays: asphalt with a liquid membrane, asphalt with a fabric membrane, asphalt without a membrane, silica fume-modified concrete, latex-modified concrete (LMC), epoxy polymer concrete, and polyester polymer concrete. This report identifies and ranks available and promising NDE technologies to assess the performance of different types of overlays and concrete bridge decks. This report describes laboratory validation on overlays for nine commonly used NDE technologies. The nine NDE technologies are: sounding, ultrasonic surface waves (USW), impact echo (IE), ultrasonic tomography (UT), impulse response (IR), ground-penetrating radar (GPR), electrical resistivity (ER), half-cell potential (HCP), and infrared thermography (IRT). This report details the results of laboratory tests validating the NDE technologies for the seven different types of overlays. Field validation using the RABITTM bridge deck assessment tool and manual testing equipment was also performed. Results from the study on which this report is based indicated that GPR was the most effective method for detecting defects in underlying concrete specimens through both bonded and debonded overlays; however, GPR could not detect overlay debonding. Results also showed that USW, IE, and UT were effective stress-wave-based methods for detecting defects under bonded overlays but not asphalt overlays. Researchers found that asphalt overlays at low temperatures (i.e., 32°F or below) improved the applicability of

This report presents the results to date of a national pooled fund study initiated in August 1996 to evaluate the long-term performance of bridges and outdoor exposure slabs damaged by chloride-induced corrosion that have concrete containing corrosion inhibiting admixtures and that had topical applications of inhibitors prior to being patched and overlaid. The study includes 156 exposure slabs, 4 bridge decks with overlays, and 1 patched bridge substructure. A total of 136 exposure slabs were constructed to simulate overlay and patch repairs, and 20 full-depth slabs were constructed to simulate new construction. Each repaired slab was constructed with one of four levels of chloride to cause corrosion. The new slabs were ponded to cause corrosion. Previous reports provide details on the construction and initial condition of the exposure slabs and the construction and initial condition of the repaired bridges. The results presented here are based on quarterly nondestructive measurements between September 1997 and June 2001, visual inspections of the exposure slabs, and tensile bond test results and visual inspections of reinforcement removed from the exposure slabs that were patched and overlaid. Overlays cracked and delaminated on exposure slabs that were fabricated with 15 lb/yd3 of chloride ion because of corrosion of the top mat of reinforcement. There was no difference in the performance of overlays constructed with and without inhibitors and topical treatments. Overlays and patches with and without inhibitor treatments placed on and in slabs with 3, 6, and 10 lb/yd3 of chloride are performing satisfactorily. However, results do not show reductions in the tendency for corrosion that can be attributed to the inhibitors. Overlays and patches with and without inhibitor treatments on and in the five bridges indicate mixed results. Corrosion is occurring in the majority of the repairs done with and without inhibitor treatments. The corrosion-inhibiting treatments do not seem to be reducing corrosion in the bridges and, in fact, may be increasing corrosion. It is not obvious that corrosion is occurring in the full-depth slabs constructed with and without inhibitors to represent new construction. The slabs do not show signs of corrosion-induced cracking after 5 years of ponding. Topical applications of inhibitors did not affect the bond strength of the overlays. Overlays containing Rheocrete 222+ and 7 percent silica fume had lower bond strengths. Overlays on base concretes with the higher chloride content had lower bond strengths. In summary, this project does not show any benefit from the use of the corrosion inhibiting admixtures and the topical applications made to the chloride-contaminated concrete surfaces prior to placement of the patches and overlays. Additional years of monitoring of the exposure slabs and bridges may provide useful results.