Reinforced concrete bridge decks are exposed to several types of deterioration processes: corrosion, alkali–silica reaction, carbonation, shrinkage, freeze–thaw actions, and so forth. The most commonly found problem is corrosion-induced bridge deck delamination. Previous studies have shown that surveys of bridges relying on a single nondestructive evaluation (NDE) technology provide limited information about the condition of concrete bridge decks. To overcome limitations of individual technologies, a complementary approach using several NDE technologies should be used in bridge deck evaluation. The presented approach utilizes a suite of NDE technologies, namely, impact echo (IE), ultrasonic surface waves (USW), ground-penetrating radar (GPR), half-cell potential (HCP), and electrical resistivity (ER). The suite of NDE technologies was implemented in the evaluation of bridge decks on nine bridges in Iowa. The NDE was complemented by ground-truth measurements on the cores extracted from all nine bridge decks. Condition assessment with the five NDE technologies has clearly shown their advantages and limitations. For example, the GPR surveys provided assessment of concrete deterioration at relatively high speeds of data collection. In contrast, IE provided high accuracy in detection and characterization of delaminations in the deck but at a lower testing speed. HCP and ER tests provided assessment of the likelihood of corrosion, whereas the USW test provided accurate assessment of the effects of deterioration processes and defects on mechanical properties, primarily the degradation of the elastic modulus. Most important, the survey showed the advantages of use of multimodal NDE surveys in the comprehensiveness of condition assessment of concrete bridge decks.

Corrosion induced bridge deck delamination is a common problem in reinforced concrete decks. While condition assessment can be done using a number of traditional and NDE methods, the presented study concentrates on a complementary use of five NDE techniques: impact echo (IE), ground penetrating radar (GPR), half-cell potential (H-C), ultrasonic surface waves (USW) and electrical resistivity (ER). Each of the five techniques has its advantages and limitations. However, each of them can contribute to a more comprehensive assessment of the condition of a deck. For example, GPR can identify deteriorated bridge deck areas, while IE can accurately detect and characterize delaminations in the deck. USW, on the other hand, provides information about material degradation through a measurement of concrete elastic moduli. Finally, H-C will provide information about the likelihood for active corrosion, while ER will assess potential for corrosive environment. There are also secondary benefits of the use of the five techniques, like e.g. mapping of concrete cover from GPR surveys. A brief overview of the techniques and their complementary use illustrated by the results from deck testing on several bridges is presented. The presented surveys were conducted on both decks (typical thickness 7 to 9 inches) and slabs (typical thickness 14-20 inches), some with an additional PC overlay. Results include delamination maps from IE, attenuation maps from GPR, modulus distribution maps from USW, H-C potential maps, and resistivity maps from ER. Some of the results are validated through a series of "ground truth" measurements, like inspection of cores taken from the decks.

No abstract

No abstract