Applicability of clay pozzolana in hydraulic backfilling of stopes at the AngloGold Ashanti, Obuasi mine

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2015-02-23
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The quest for a cheaper alternative or supplement to ordinary Portland cement as binder in the backfilling of mined out stopes in underground mines motivated this study. Clay pozzolana has been proven to substitute about 30% of Portland cement in general construction works and is cheaper. However, very little is known about its applicability in mine backfill. This study therefore sought to investigate whether clay pozzolana could be applied in the case of hydraulic backfill in the AngloGold Ashanti, Obuasi Mine. Samples of the classified tailings from the AngloGold Ashanti, Obuasi Mine were prepared with different amounts of ordinary Portland cement and clay pozzolana combinations into 50mm diameter by 120mm high cylindrical specimens and then tested for compressive strength after curing under humid conditions for various periods. Samples of the tailings were also subjected to particle size distribution and sulphate content analyses. The results indicated that generally, backfill with 10%, 25%, 30% and 35% of the ordinary Portland cement content replaced with clay pozzolana had strength values comparable to those obtained for samples containing ordinary Portland cement alone. Ten per cent (10%) pozzolana content replacement showed consistent maximum strength characteristics after curing beyond 7 days. Therefore, in terms of strength; it is recommended that 10% of ordinary Portland cement could be substituted with clay pozzolana in the hydraulic backfilling of voids in the AngloGold Ashanti, Obuasi Mine. The particle size distribution analysis indicated that the tailings are suitable in terms of its drainage characteristics for hydraulic backfilling of voids. The results of the sulphate content analysis indicated that the sulphate content of the tailings obtained from AGA, Obuasi Mine for the study was higher compared with the upper limit set by ASTM Standard C94 and European iv Standard EN 1008.Using 2013 as the baseline, an amount of Gh¢12.00 would be saved on every tonnage of cement used. This represents 3% of the amount of money spent on every tonnage of cement used.
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A Thesis Submitted to the Department Of Materials Engineering In Partial Fulfilment of the Requirements for the Award of Master of Science Degree in Environmental Resource Management.
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