A process is disclosed for forming lightweight aggregate pellets having a density of less than about 60 lbs./ft..sup.2. The first step of the process is to form an admixture which includes fly ash, cement and filler. By weight percent of the admixture formed, the admixture includes greater than 60% fly ash, 1-25% cement and 1-10% filler. Water and a chemical accelerator are added to the admixture in a pelletizing device. By weight percent of the aggregate formed, about 1 to 18% water is added and between about 0 and 3% chemical accelerator is added by weight of the cement used in the admixture. The aggregate pellets are then removed from the pelletizing device and cured with an oxygen containing gas, such as air, at a temperature of less than about 300.degree. F.