Using scheelite residue and rice husk ash to manufacture lightweight aggregates
Abstract Over the years, the use of expandable clays has supported the world production of lightweight aggregates (LWAs) however the gradual lack of natural resources requires using more sustainable practices. Thus, the aim is to develop LWAs suitable for use in structural lightweight concrete and other engineering services, using scheelite residue (SPR) and rice husk ash (RHA) Studies show that the production of these residues is increasing, their environmental impacts are significant, and their properties favour the development of LWAs. However, no research was found on the use of SPR in LWAs. Raw materials were characterised by laser granulometry, scanning electron microscopy, X ray fluorescence, X ray diffraction and simultaneous thermal analysis. Then, 23 mixtures were formulated, from the replacement of clay by up to 100% residues. The samples were sintered at 1100, 1150, 1200 and 1250 degC. The manufactured aggregates were characterised by the bloating index (BI) mass loss (LOI) particle density (rd) water absorption (WA24H) crushing strength (S) mineralogical composition and microstructure. Finally, the feasibility of using the manufactured LWAs was evaluated, based on a comparative analysis with the properties of a commercial LWA. The resulting aggregates showed: (BI) maximum of 77.44% (LOI) of up to 12.0% (rd) varying between 0.86 and 1.80 g/cm3, (WA24H) minimum of 2.0% and (S) up to 13.5 MPa. Overall, 42 specimens demonstrated properties at least similar to the commercial LWA ones. The results reveal that it is technically feasible to use SPR and RHA to produce LWAs.