This work investigated the recycling of fly ash waste and cullet as the raw materials for lightweight bodies produced by heat treatment and using sodium silicate as the binder. Borax was mixed with fly ash and cullet, and put into the block in dimension 10x10x2 cm3. The lightweight materials thus produced were then sintered at temperature of 800 °C. Density, compressive strength and thermal conductivity were determined. Borax showed a positive sintering effect on the porosity of lightweight material during the heat process. The compressive strength of lightweight material diminished with the reduction of density and thermal conductivity. Lightweight material manufactured with borax showed the lower density and thermal conductivity accompanied by the higher compressive strength. The test results indicated that using fly ash and cullet as the raw material with borax could obtain the lightweight material, thus enhancing the possibility of its reuse in a sustainable way.

Four formulas of the stoneware bodies were formulated with and without an increasing amount of lithium oxide. The bodies were designed to vitrify at the temperature lower than 1150°C. A comparison on the physical properties and the phase formation of the bodies after firing at the temperature of 1100°C, 1150°C, and 1200°C was studied. The experiment results showed that the bodies containing lithium oxide vitrified at lower temperature and showed less variation in water absorption, density, and shrinkage values in the firing range 1100-1200°C. The XRD results showed that, at 1100°C, all the bodies composed of mullite, albite, and quartz. A reduction in the <em>amount</em> of albite and quartz associated with mullite formation was observed when increasing the amount of lithium oxide or the temperature. Furthermore, the body with lithium oxide tended to have higher value of the Modulus of Rupture.