Patent ID: 7927420

Claim:
A building material composition useful as a fire door core, comprising a dewatered, dried and cured composition consisting essentially of a fluid aqueous slurry of calcined gypsum, paper fibers, a water insoluble organic binder, fiber reinforcement and a set retarder wherein said aqueous mixture contains on a dry weight basis, about 50 to 72 percent of the calcined gypsum, about 25 to 45 percent of the paper fiber, about 0.5 to 5 percent of the water insoluble organic binder, about 0.5 to 2 percent of the fiber reinforcement and up to about 0.3 percent of the set retarder, wherein the fluid aqueous slurry can be press molded to dewater the slurry and wherein the building material composition has a density of from 18 to about 23 pounds per cubic foot.