EXTENDING LIFE OF CONCRETE BRIDGE DECKS THROUGH EARLY DETERIORATION DETECTION BY NDE METHODS

Corrosion induced bridge deck delamination is a common problem in reinforced concrete decks. This is especially pronounced in the U.S.A. where far the highest percentage of concrete decks are bare decks. The prevailing inspection practice of bridge decks relies on visual inspection and the use of simple nondestructive evaluation (NDE) tools, like chain drag and hammer sounding. The presented study concentrates on a complementary use of five NDE techniques for the detection of three deterioration/defect types: corrosion, delamination and concrete degradataion. The NDE technologies used include: impact echo (OE), ground penetrating radar (GPR), half-cell potential (Hop), ultrasonic surface waves (usw) and electrical resistivity (ER). Each of the five techniques can contribute to a more comprehensive assessment of the condition ofa deck. HCP provides information about the likelihood of active corrosion, while ER will assess the potential for corrosive environment. IE can accurately detect and characterize delaminations in the deck, while GPR can identify deteriorated bridge deck areas, in some cases matching the position of delaminations. Finally, the usw provides information about the material degradation through a measurement of concrete elastic modulus. One of the NDE features is that the results are quantitative. This allows objective assessment of the condition ofa deck and, thus, objective comparison of bridges on the network level. In addition, NDE allows detection of problems at far earlier stages of deterioration than the traditional approaches. A brief overview of the techniques and their complementary use, illustrated by the results from deck testing on several bridges, is presented. Results include delamination maps from IE, attenuation maps from GPR, modulus distribution maps from usw, HCP potential maps, and resistivity maps from ER.