Elastomeric Concrete Plug Joints: A New Durable Bridge Expansion Joint Design

About the report:

Expansion joints are important components of bridges that accommodate the movements between deck spans that result from thermal loads, traffic loads, and other environmental factors. Experience shows that joints undergo premature deterioration on a regular basis, thus leading to unexpected problems caused by leakage of water and other corrosive chemicals over the components of the superstructure and substructure, thus leading to premature deterioration of those components.

Millions of dollars have been spent by the Virginia Department of Transportation (VDOT) over more than 50 years for repairs and replacements of joints. Several types of closed joints have been developed and installed in the past three decades to combat this problem. In addition, jointless details at piers and abutments have been developed and installed in the same time period to eliminate the need for joints. However, the issue persists. VDOT’s Structure and Bridge Division has developed a new design for a flexible joint system with bonded and debonded zones. An elastomeric concrete material acts as the load-bearing surface and the component that allows free expansion and contraction. This joint system has been installed in selected pilot bridges on secondary roads for observation. This study evaluated the performance of this joint system and detailed the challenges faced in developing it.

The elastomeric concrete plug joint system was successfully implemented in five pilot bridges in Virginia. Short-term performance of the system was satisfactory under Virginia weather conditions. Rutting during the summer months has not been observed even though one of the elastomeric materials had failed in the laboratory testing. Expansion cracking during the winter months was not observed in the first year after installation. It was determined that shore durometer hardness values can be used as a preliminary filter to select elastomeric material with resistance to permanent indentation. Dynamic modulus testing can be used as a measure of the toughness and flexibility of elastomeric concrete material under different temperatures. However, these tests do not give a complete picture of the material properties, so engineering judgment is also necessary in order to make decisions regarding the elastomeric materials. The Virginia Transportation Research Council and VDOT’s Structure and Bridge Division should continue to monitor visually the performance of the elastomeric concrete plug joint systems installed during this study and continue to evaluate new elastomeric concrete candidates for the joint system. Further, the Virginia Transportation Research Council and VDOT’s Structure and Bridge Division should expand the trials to other VDOT districts for various exposure conditions.

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