VoidCap is a polystyrene expansion cap with a removable top that can be placed over all types of the expansion joint. After the concrete is poured, the top of the VoidCap is level with the surface of the slab. After the surface of the concrete is finished, the top portion of the VoidCap can be removed to allow a void approximately 1/2" deep. Any type of self-leveling caulk can be placed into the void, sealing the joint from surface moisture.