PREPARATION OF ONE-PART GEOPOLYMER FROM THERMAL-ALKALI ACTIVATED RED MUD

Red mud, a high-volume industrial waste generated worldwide through the Bayer digestion process, has recently drawn attention as a suitable precursor for production of geopolymers. However, in seeking high-volume production and utilisation of this material in valuable applications, the reactivity of red mud needs to be better controlled, and particularly the availability of aluminium must be enhanced. In this study, a "just add water" geopolymer precursor has been produced through an alkali-thermal activation method, to avoid the need for addition of a secondary alkaline solution in preparing geopolymers. The results show the incorporation of alkalis during the thermal activation at 800 degrees C of red mud favours the formation of hydraulic tricalcium aluminate (C(3)A), and a peralkaline aluminosilicate which contains excess alkalis in its solid form and improves the availability of Al during the hydration process. The formation of zeolite Na-A and double ring structural Si-O-Si bonds indicate that reaction of the one-part geopolymer is effectively occurring upon hydration.