It is known to fill cavities in underground mines using a settable mixture including cement, bentonite and water, for the purposes of supporting the roof, stabilizing underground roadways, sealing areas to prevent or control access of air, etc. A number of proprietary mixtures are marketed, the most modern of these have high water-to-solids contents and incorporate high alumina cement.
Tailings, in the context of coal mining, are the very fine residues from coal processing, and comprise particles of less than 0.5 mm size, of dirt and a proportion of coal, and water, the water content being variable to over from 45% to more than 70% by weight. Modern mining techniques, involving mechanization of coal mining and transport, produce even larger quantities of fines, but environmental and safety considerations currently mitigate against the most economical method of disposal of fines, by lagoon settling. It is known to dry tailings by various methods, and also to stabilizing, at least to some extent, tailings by the incorporation of cement, and to use the stabilizing material as a low quality material in civil engineering or the stabilizing material is simply tipped.