Impermeable Asphalt Concrete Layer to Protect and Seal Concrete Bridge Decks

Deterioration of the concrete bridge deck is one of the most significant problems affecting the service life of bridges in the United States (U.S.). The early failure of asphalt pavement overlays on concrete bridge decks with spray-on waterproofing membranes has been recognized as a significant issue by the Oregon Department of Transportation (ODOT). Potential reasons for the failure of the asphalt overlays were thought to be the poor adhesion between the waterproofing membrane and the asphalt-wearing course, and the material properties of the asphalt layer. Moisture penetration into the asphalt overlay and standing water on the concrete bridge deck result in expansion and contraction at the interface on the bridge deck during freeze-thaw cycles. Expansion and contraction because of freeze-thaw cycles cause debonding at the interface and result in an increased rate of deterioration for the asphalt concrete overlay. Additionally, the de-icing salts used to prevent hazardous roadway surfaces in the winter permeate into the deck and cause corrosion of the steel reinforcement, weakening the structural integrity of the bridge. The main goal of this study is to develop an impermeable asphalt mixture with high cracking and rutting resistance that can seal and protect the concrete bridge deck by preventing water and de-icing salts from penetrating into the concrete deck. Permeability of developed asphalt mixtures was quantified by permeability testing and moisture sensor measurements. Rutting and cracking resistance of the developed impermeable asphalt mixture strategies were also evaluated by conducting flow number (FN) and semi-circular bend (SCB) tests in the laboratory.