The investigation of the production of lightweight aggregate for use in concrete blocks, pre case concrete structural shapes and in monolithic structures and of the development of processes and the utilization of various available raw materials for that purpose, is of special interest to the Bureau of Mines. The potential demand for these aggregates is extremely large and in many localities serious shortages exist. Because of such interest and critical shortages, the Industrial Research and Development Division of the Office of Technical Services, US Department of Commerce, has deemed it advisable to enter into contract with the Bureau of Mines to assist in the research aimed at the stimulation of the industrial production of larger quantities of lightweight concrete aggregates.