The primary purposes of this study are to investigate the deterioration characteristics of concrete bridge decks in Korea expressways and to develop an advanced condition assessment methodology with an air-coupled ground penetrating radar (GPR) system.
Firstly, nineteen actual bridge decks paved with asphalt concrete, which is the preferred overlay style in South Korea, were surveyed to develop a diagnostic index by taking 247 core samples on Korea expressways. Their deterioration characteristics were analyzed in various aspects such as pavement condition, waterproof layer, corrosion and cover concrete of reinforcing steel, and chloride contents in the concrete. It has been duly noted that the deteriorations of concrete decks are mainly attributed to freeze-thaw action. The severity of deterioration is closely related to waterproofing quality (and/or the adhesion of pavement and deck concrete), and the damaged depth is significantly correlated to chloride contents of cover concrete of top rebar.
Secondly, advances are made in the condition assessment of concrete bridge decks using GPR technique, which is getting the limelight in domestic and overseas. Fifty three actual concrete bridge decks on Korea expressways were scanned using an air-coupled GPR system. A sensitivity study was performed to investigate influencing factors on the relative permittivity of concrete as a means of concrete condition assessment of bridge decks in South Korea. As a result, approximating formula was established to relate the influencing factors (i.e., water contents and concrete ages) to the relative permittivity. Additionally, GPR reflection signal attenuation, generally used as a means of condition assessment of bridge decks by traditional researchers in the world, was affirmed to be an effective factor of evaluating concrete bridge decks on Korea expressways. Accordingly, improved condition evaluation models are proposed for better interpretation of relative permittivity values by calibrating the effects of the two influencing factors (i.e., water contents and concrete ages) and GPR reflection signal attenuation by calibrating the effect of concrete cover depth to top reinforcing steel and asphalt concrete overlays.
The validity of the proposed models was verified on the concrete bridge decks in public service. According to the test results using GPR, deck condition was effectively evaluated with the relative permittivity of concrete, which functioned as an indicator of water leakage at the interface between pavement and concrete deck, and the attenuation of radar energy through cover concrete, which was positively correlated with deteriorated depths of the concrete decks.