The generic term "geofoam" is often used to describe expanded polystyrene formed into low-density cellular plastic solids used as lightweight, stable, inert, and environmentally safe blocks. The manufacturing process begins by exposing polystyrene resin beads, containing a hydrocarbon blowing agent, to steam. The polymer softens and the blowing agent expands the beads to form "pre-puff". These expanded beads are then blown into large rectangular block molds. Steam is injected into the molds, where the beads expand further and fuse together to form the final product. The specification was revised to update the physical requirements of expanded polystyrene fill, improve quality assurance procedures, and to reflect construction best practices.
