Overlay Types Used as Preventive Maintenance on Tennessee Bridge Decks

Of all the components that compose a highway bridge, the bridge deck usually deteriorates the most quickly and requires the most maintenance and repair because of its exposure to detrimental conditions. Several preventive maintenance techniques are available to retard bridge deck deterioration and thus prolong service lives. Of these techniques, types of bridge deck overlays are investigated. As preventive maintenance, an overlay provides a protective layer between the bridge deck and the detrimental conditions that promote deterioration. In general, this protection enhances the material properties of the overlay, which may include low permeability and resistance to chemical attack as well as added thickness. The overlay procedures used for bridge decks in Tennessee are investigated from information about overlay types and their usage obtained through several sources, including interviews with Tennessee Department of Transportation personnel who are experienced in bridge maintenance. Four types are identified: asphalt, reinforced portland cement concrete, nonreinforced polymer-modified concrete, and thin bonded overlays. Each overlay is described and typical applications, bridge deck preparation, general construction techniques, special considerations, expected service lives, and average costs are discussed. Expected service lives ranged from 15 to more than 30 years, and average costs ranged from $30 to more than $100 per square yard. All overlay types are useful and appropriate under different situations.