Novel geopolymeric building materials through synergistic utilisation of industrial waste

Abstract

Synergistic utilisation of major industrial wastes generated in India, namely fly ash, blast furnace slag and red mud, has been explored to develop novel building components using geopolymerisation. These include: (a) high strength cements (b) self glazed wall tiles, and (c) pavement tiles. Fly ash was used as main source of silico-aluminate for geopolymerisation. Granulated blast furnace slag (GBFS) and red mud were used individually or in combination with fly ash to tailor properties of the developed components. Chemical and mechanical activation have been judiciously incorporated in the processing schemes through an understanding of processing-structure-property relationships. Improvement in the reactivity of fly ash by mechanical activation using highenergy mills was found to results in the formation of a compact microstructure during geopolymerisation leading to high compressive strength (above 100 MPa) in geopolymer cements. The cements also exhibited improved setting time and a very low autoclave expansion. In self-glazed wall tiles, the hard impervious glazed surface was obtained at temperature lower than 150°C by controlling the particle size distribution of solid reactants, viscosity of slurry and reaction atmosphere. The self-glazed surface showed the presence of gismodine (Na-plagioclase) phase which was absent in the main body of the tiles. In pavement tiles, fly ash and granulated blast furnace slag were used to give structural framework, whereas red mud was used to supplement the iron oxide for colouring effect and alkalis. The setting and hardening occurred due to formation of cementitious A-S-H and C-S-H gel (A = Al2O3, S = SiO2, C = CaO, H = H2O). The technologies have been developed at bench scale and efforts are underway for scaling up to pilot plant level.