One-Part Geopolymers Based on Thermally Treated Red Mud/NaOH Blends

In this study, one-part just add water geopolymer binders are synthesized through the alkali-thermal activation of the red mud which is relatively rich in both alumina and calcium. Calcination of the red mud with sodium hydroxide pellets at 800 degrees C leads to decomposition of the original silicate and aluminosilicate phases present in the red mud, which promotes the formation of new compounds with hydraulic character, including a partially ordered peralkaline aluminosilicate phase and the calcium-rich phases C(3)A and -C2S. The hydration of the one-part geopolymer leads to the formation of zeolites and a disordered binder gel as the main reaction products, and the consequent development of compressive strengths of up to 10MPa after 7d of curing. These results demonstrate that red mud is an effective precursor to produce one-part geopolymer binders, via thermal and alkali-activation processes.