Synthesis of geopolymer composites using bauxite residue-based spheres as aggregate: Novel and eco-friendly strategy to produce lightweight building materials
Zélia Alves, Luciano Senff, Konstantinos Sakkas, Iakovos Yakoumis, J.A. Labrincha, Rui M. Novais
Abstract
In this study, and for the first time, highly porous red mud-based geopolymer spheres were produced, through a very simple and scalable procedure, and used as lightweight aggregate in the synthesis of geopolymer composites. To further demonstrate the potential of this unexplored route, a comparison with composites containing expanded perlite and expanded vermiculite was also performed. The sample produced with 85 vol% of spheres showed the lowest geometric density (0.84 g/cm3) amongst the studied composites, coupled with a suitable compressive strength (1.0 MPa), low thermal conductivity (175 mW/m K), and excellent thermal stability after exposure to 1000 °C for 2h. The much lower production temperature (80 °C), compared with the commercial expanded aggregates (above 650 °C), and the reuse of significant amounts of bauxite residue (strategy aligned with the circular economy) enables the production of eco-friendly lightweight aggregates for the building sector.