The Virginia Transportation Research Council was engaged on two occasions by the Staunton District Bridge office of the Virginia Department of Transportation to assist with the evaluation of concrete cover depth in newly constructed reinforced concrete bridge decks. Initial observations with cover meter taken by VDOT inspection personnel suggested that significant areas of inadequate reinforcement cover existed on each of the decks after concrete placement. Research Council personnel conducted surveys using cover meter at select locations to establish the probability that inadequate cover existed. Linear scans of the decks using ground penetrating radar provided more comprehensive documentation of the extent and locations of shallow cover. The scans were conducted using a cart-based 1.6 GHz ground-coupled antenna. GPR results were correlated with cover meter readings, and in one case corroborated by drilling to the reinforcement for physical measurement. VDOT personnel were concerned that the inadequate cover would compromise the service life of the decks on these new structures, particularly with respect to potential for deicing salt-induced corrosion. Based on the findings of the survey, VDOT required the respective contractors to provide supplemental thin polymer concrete overlays to spans constructed with inadequate cover to preserve the intended design life of the decks. Two spans of each bridge were overlaid and the direct value of the overlays was approximately $25,000 to $30,000 each. The application of the overlays occurred prior to opening of the structures to traffic, thereby avoiding future costs of maintenance of traffic and user costs that would be imposed, should such overlays be implemented after acceptance and introduction of the structures into service. The potential savings of this technical assistance effort is not directly quantified. However, the direct value of the overlays far exceeded the estimated time invested by the researchers for the two structures, which was approximately 40 man-hours, worth approximately $2,300.
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