Additives for strengthening backfill materials in steep coal-seam mining. Open File Report, August 1984-June 1985

A testing program was conducted to design a cemented backfill for hydraulic placement in underhand cut and fill mining of a steeply dipping coal seam. The testing evaluated the use of three different backfill aggregates, locally available at the coal mine, with portland cement and five different pozzolans, including a Class F fly ash, a Class C fly ash, a cement kiln dust, and ground smelter slag. Both viscosity and uniaxial compressive strength of backfill mixtures with different pozzolan and portland cement contents were used to evaluate their suitability. Based upon the results of preliminary testing, an optimum mixture of alluvial sand with 6% portland cement and 10% Class F pozzolan was chosen for further compression testing.