Ph.D. Tezi Görüntüleme | |||||||||||||||||||||
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| Summary: In recent years, paste backfill (CPB) has gained importance since all the mill tailings produced in mineral processing operations can be placed safely into the underground openings created due to ore production. This reduces the tailings disposal and rehabilitation costs, and renders the mining operations more environmentally friendly. CPB is an engineered mixture of mill tailings, a hydraulic binder and mixing water. The physical, chemical and mineralogical properties of each components of CPB affect its strength and stability. Some problems in long-term stability of CPB are known to be often experienced in practice when the mill tailings with high sulphide content are used.In this study, the effects of binder type and dosage, water-to-cement ratio and, mineral and chemical admixtures on the mechanical performance and rheological properties of CPB prepared from sulphide rich-mill tailings were investigated. The CPB specimens prepared under the different test conditions were subjected to the uniaxial strength and deformation tests over 7-360 days of curing periods. Ordinary Portland cement (CEM I 42.5), Portland compose cement (CEM II/A 42.5) and sulphate resistant cement (SDC 32.5) at 5% binder dosage were found to be not suitable binders for use; albeit, only SDC 32.5 alleviated the loss of strength of CPB samples in the long term. Increasing binder dosage or decreasing water-to-cement ratio appeared to produce a beneficial effect on the strength and stability of CPB samples. The addition of FT, AT and ACM (10-30 wt%) as a partial replacement of CEM I 42,5 were observed to aggravate further the strength losses of CPB samples. However, YFC, UK, KP and SD (5-60%) appeared to improve the long-term performance of CPB samples. In the short and long term tests, NA, SA and HA as water-reducing admixtures have produced a positive effect on the paste backfill strength. SEM analysis of CPB samples revealed that the strength losses in the long term could be attributed to the formation of secondary gypsum.Key Words: Paste Backfill, Sulphide Tailings, Binder Type, Mineral and Chemical Admixtures, Acid and Sulphate Effect, Uniaxial Compressive Strength | |||||||||||||||||||||