Bridge Approach/Anchor Slab Joint Evaluation

摘要

Portland cement concrete pavements between bridges expand in warm weather andcontract when cooled and due to shrinkage of concrete. Pavement movements have to be accommodated close to the bridge for the safety of the bridge structure. Reinforced anchor slabs with the monolithic lugs underneath, are provided to resist the pavement movement by the passive soil pressure after mobilization. Nevertheless, additional positive relief is provided to the joint between the approach slab and the anchor slab, which butts up against the PCCP. The function of this joint is crucial to the safety of the bridge. A material or device that will not let water and debris inside the joint and at the same time allows sufficient expansion and contraction under traffic and weather conditions, is required to seal the joing. ADOT Construction and Maintenance staff have been observing the ineffectiveness of the joint in several locations on Arizona Freeways, due to debris and water penetrating the joint. This prompted ADOT to undertake the evaluation of the existing joint and to improve or modify the joint to make it more functional and efficient. Based on the study of the available joint systems and materials, five new solutions for the joint were devised and proposed. The new joints have improved quality in the material of the sealant (low modulus hot poured sealant, silicone sealant and membrane foam sealant) and compression and strip seals. Adaptation of these to the existing joints is also discussed. Joint preparation requirements and termination treatments at side barriers are also addressed.