ABSTRACT
Precast concrete product as PC slab for bridge has been recently employed as the replacement for deteriorated RC slabs due to the corrosion of steel reinforcement by deicing salt. Although half-cell potential method as an electro-chemical technique has been normally employed for the diagnosis of steel reinforcements in concrete, the applicability for precast PC slab remains unknown because of the double layered arrangement of the steel reinforcements and the steam cured high strength nature. In addition, the impact of frost damage combined with chloride ions penetration in precast concrete slab has been little studied and needs further study. In this study double layers of rebars to simulate the arrangement of reinforcements in roadway slab were adapted in concrete specimen. A 10% sodium chloride solution tank was placed on the top surface of specimen to simulate the roadway spray of deicing salt. Steam curing at a maximum temperature of 65 degrees Celsius was applied to various mixed concrete specimens of the water to binder ratios of 0.35 and 0.4 in which high early strength Portland cement was used. In addition, fly ash was replaced for the cement by 20 % (FA) and granulated blast furnace slag was replaced by 50% (BB), respectively. As an electro-chemical technique to monitor the corrosion embedded in the concrete specimens, the half-cell potential and polarization resistance were measured. This study implements six modes of connecting the either or both upper (U) and down (D) bars to the reference electrode (RE) on either top (T) or bottom (B) concrete surfaces, namely UT, UB, DT, DB, JT and JB. It was expected that the upper bar would be corroded first and highlighted that among six modes JB that was electrically connecting both up and down bars to the RE on the bottom surface could find the corrosion. This indicates that the corrosion of the upper steel reinforcement can be detected in such a way that the RE is attached on its bottom surface without hindering vehicle traffics on the top surface of concrete slab.
