Abstract: An apparatus for filling joints in precast concrete structures includes a core that has exceptionally low creep and conforms to ASTM D 1752 made of controlled particle size composites of recycled cellular rubber and plastic materials in the form of a rectangular slab. Holes are drilled through a central area and countersink recesses are formed around the holes. An outer coating of a thermoplastic polyurethane/polyurea elastomer system of a thickness of 0.075 inch covers the slab and countersink recesses. The coated core is abrasion and UV resistant while having the creep characteristics needed to make a dam expansion joint filler.