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This paper is based on a research study aimed at determining the relative effectiveness of three bridge deck protective systems (i.e., latex-modified concrete (LMC) overlay, low-slump dense concrete (LSDC) overlay, and cathodic protection (CP) in preventing or halting reinforcing steel corrosion and corrosion-induced deterioration in salt-contaminated concrete. The paper documents the results of testing five LMC, five LSDC, and two CP bridge decks. The test bridges had experienced severe corrosion-induced deterioration and/or severe salt contamination before protection. At the time of testing the average age of both the LMC and LSDC overlays was about seven years, and the average age of the CP installations (slotted system) was five years. Also, among the concrete overlaid decks, seven had been subjects of previous similar investigations. Thus, the study determined changes in the effectiveness of concrete overlay protective systems with time.
The mode of internal concrete fracture caused by reinforcing steel corrosion and its magnitude were determined. Performance information was expressed in terms of corrosion-induced deterioration as well as rate of corrosion-induced deterioration. A criterion was established for the condition beyond which deterioration impairs deck serviceability. Accordingly, the effective service lives of the rehabilitated/protected decks were estimated. Also, the performance information was analyzed for factors affecting the condition of a rehabilitated/protected deck. Overlay surface cracking and overlay thickness were found to affect the corrosion-induced deterioration in the concrete overlaid decks. Correlations were made between those factors and the deterioration. In CP decks various types of concrete deterioration were found, their magnitudes were measured, and their causes were identified. Those types of deterioration, generally, were not related to corrosion of reinforcing steel. The cost-effectiveness of concrete overlay and cathodic protection strategies were determined on the basis of bridge deck life-time costs and compared.
bridge deck, concrete, reinforcing steel, corrosion, overlay, cathodic protection, rehabilitation, protection, cost-effectiveness
Senior Engineer, Wilbur Smith Associates, Falls Church, Virginia
Head, University of Illinois at Urbana-Champaign, Urbana, Illinois