Thermal activation mechanism and pozzolanic activity characteristics of coal flotation tailing

Abstract

Coal flotation tailings (CFT) was calcined to be used as a supplementary cementing material. CFT and its calcined products were characterised by thermogravimetric analysis (TGA), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy. The pozzolanic activity of the calcined products was analysed by the strength activity index. The hydration products of blended cement were characterised by TGA, XRD and scanning electron microscopy to explain the influence of calcined products on cement hydration. The results showed that calcination treatment destroyed the structure of illite–kaolinite mixed-layer clays from CFT and enhance pozzolanic activity. Moreover, the highest pozzolanic reactivity was obtained at 850°C because the recrystallisation effect increased chemical stability above 900°C. The impact of calcined CFT on the hydration of cement in a blended system was the combination of micro-aggregate effects and the pozzolanic reaction. The experimental results indicated that calcined products of CFT had good pozzolanic activity, which provided the feasibility of large-scale recycling utilisation of CFT.