Preparation of aggregates based on waste foundry sand: Reuse of calcined clay

Used calcined clay, waste foundry sand (WFS), was adopted to prepare aggregates with the addition of clay, alumina powder, and bran. Bulk density, porosity, cold crushing strength, phase compositions, microstructure, and thermal conductivity were investigated. Thermal calculation was adopted to assess the generation of the liquid phase during sintering. In the specimens composed of WFS and clay, the increase in clay concentration led to a decrease in cold crushing strength even if the variation in bulk density was not obvious. When WFS, clay, alumina powder, and bran were adopted in manufacturing aggregates, the addition of bran influenced the phase composition of the samples because of the formation of pores. With an increased WFS content, the cold crushing strength improved due to an increase in the amount of liquid phase during the sintering process. The thermal conductivities obtained from the samples by mechanical pressing were ideal and showed the influence of heat shielding effect from zircon.