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

Abstract

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°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 C3A and α‐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 10 MPa after 7 d of curing. These results demonstrate that red mud is an effective precursor to produce one‐part geopolymer binders, via thermal and alkali‐activation processes.

Alkali-activated materials

“…Some definitions of alkali-activation also include MgO, CaO and/or Ca(OH)2 as potential activator compounds. The production of a one-part mix alkali-activated binder system has been demonstrated via cocalcination or intergrinding of various aluminosilicate powder precursors and solid activators, usually either an alkali carbonate, silicate or hydroxide [40][41][42][43][44]. Environmental benefits which may be obtained by such a processing route have also been highlighted [45].…”

Waste glass from end-of-life fluorescent lamps as raw material in geopolymers

“…The production of cement is one of the main sources of CO 2 emissions, due to the decomposition of calcium carbonate (Benhelal et al, 2012), alongside the combustion of fossil fuels. For every ton of cement produced, around 0.85 ton of CO 2 are emit ted (Ke et al, 2015) which accounts for 5 7% of the total CO 2 anthropogenic emissions (Chen et al, 2010). These data show the need to find more sustainable materials that can mitigate these CO 2 emissions, and hence contribute to the European Commission directives imposing significant emissions abatement by 2030 (Torres Carrasco and Puertas, 2015).…”

Co-disposal of MSWI fly ash and Bayer red mud using an one-part geopolymeric system

“…Approximately 120 million tons of RM is being generated annually around the world [31], imposing a great burden on environment protection. In our previous work, the RM was pretreated through alkali-thermal activation and turned into a one-part geopolymer precursor, which could be used in a blending process by only adding water [32,33]. The RM pretreated through alkali-thermal activation could be recycled for cementitious materials, which reduced the pollution risks of land disposal to the environment.…”