Research was undertaken by the Bureau of Mines to determine the technical feasibility of producing lightweight aggregate from the waste glass fraction of municipal incinerator residues. Tests were conducted to determine the amount of optimum size of glass, the amount of sodium silicate, and the method used to form the material to be expanded. The most suitable mixture, 78 percent glass, 20 percent clay, and 2 percent sodium silicate, was pelletized and then expanded by exposure to a temperature of 1,550 deg f for 15 minutes. The resulting lightweight material had a bulk density of 38 lb/cu ft and exhibited excellent pore structure. Concrete test cylinders made from the lightweight aggregate had a unit weight of 104 lb/cu ft and a compressive strength of 2,550 lb/sq in after a 28-day steam cure. Work done with the University of Alabama.