Abstract: An expansible caulking material in strip form is disclosed suitable for use in sealing joints between vertical panels, and packing wide expansion joints occurring in decks of parking garages, bridges, airport runways and the like, with a shortened expansion time particularly for use in cold locations where the expansibility by reason of the adhesive impregnant would be unduly delayed. The caulking material comprises compressed and expansible strips of open cell plastic foam with one or more wires or strips therewith with the foam normally retained in compressed condition until ready for use, and in which an electric current is applied to the ends of the wires or strips to supply heat to speed up the expansion.