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    Influence of silica fume on mechanical property of cemented paste backfill
    (Elsevier Sci Ltd, 2022) Eker, Hasan; Bascetin, Atac
    The cemented paste backfill (CPB) method, which is the most preferred method for tailings storage, is one of the most used methods for the disposal of mine tailings. However, the high rate of cement usage increases the costs. In this study, whether silica fume (SF), which is a pozzolanic material, can be used as a substitute instead of cement was investigated based on mechanical parameters or not. As a result of the experiments, it was determined that SF substituted for portland cement (PC) increased the strength of paste backfill mixtures prepared in a certain cement ratio. In addition, it was determined that SF substitution in CPB increased the durability of mixtures against sulphate attacks as it did in concrete. With the use of SF, savings of up to 20% were achieved in the amount and cost of cement used in CPB. Besides, using it without the pulverizing process required for pozzolanic materials used in other studies had a positive effect in terms of time and cost. Moreover, the use of SF in CPB mixtures resulted in less energy use and less greenhouse gas emissions, and a reduction of environmental pollution caused by SF tailings.
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    The investigation of geochemical and geomechanical properties in surface paste disposal by pilot-scale tests
    (Taylor & Francis Ltd, 2022) Bascetin, Atac; Adiguzel, Deniz; Eker, Hasan; Tuylu, Serkan
    Today, seepage control in tailings dams has become an important problem due to the increased production in mining sites. Although very techniques have been developed to solve this problem, research in this field continues. The reason for this is that there is an ongoing search for a one hundred percent successful method to prevent seepage. In this study, the geochemical and geomechanical properties of paste material stored by the surface paste disposal (SPD) method were investigated by pilot field tests. To determine the effects of cement and pozzolanic materials on the geochemical and geomechanical properties of the paste, 2 different pilot-scale storage designs were observed for about 1 year, with no additives (reference) and binder added to some layers (cement and fly ash). Based on the data derived from the former laboratory investigations and with no additives and with a few layers of cement and fly ash, the two different designs were applied on a pilot scale near the existing tailings dam of a currently active mining enterprise. These designs were observed in inland conditions for about 1 year to determine the effects of seasonal changes on the material. The seepage analysis, surface crack densities, microstructural properties, consolidation, and cohesion values of these designs, which are directly exposed to atmospheric effects, were determined during the study period. According to the results obtained, the use of cement improved the volume compressibility coefficient of the material by approximately 25% compared to the reference design. However, the use of fly ash alongside cement improved the volume compressibility coefficient by about 75%. In conclusion, the use of cement made the material more resistant to external factors, and the usability of fly ash, which was used at a 50% replacement ratio with cement to bring down the cost, for long-time storage in the industry was demonstrated within the scope of the study.
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    The study of strength behaviour of zeolite in cemented paste backfill
    (Techno-Press, 2022) Eker, Hasan; Bascetin, Atac
    In the present study, reference samples were prepared using ore preparation facility tailings taken from the copper mine (Kure, Kastamonu), Portland cement (PC) in certain proportions (3 wt%, 5 wt%, 7 wt%, 9wt% and 11 wt%), and water. Then natural zeolite taken from the Bigadic Region was mixed in certain proportions (10 wt%, 20 wt%, 30 wt% and 40 wt%) for each cement ratio, instead of the PC, to prepare zeolite-substituted CPB samples. Thus, the effect of using Zeolite instead of PC on CPB's strength was investigated. The obtained CPB samples were kept in the curing cabinet at a temperature of 25???C and at least 80% humidity, and they were subjected to the Uniaxial Compressive Strength (UCS) test at the end of the curing periods of 3, 7, 14, 28, 56, and 90 days. Except for the 3 wt% cement ratio, zeolite substitution was observed to increase the compressive strength in all mixtures. Also, the liquefaction risk limit for paste backfill was achieved for all mixtures, and the desired strength limit value (0.7 MPa) was achieved for all mixtures with 28 days of curing time and 7 wt%, 9 wt%, 11 wt% cement ratios and 5% cement ??? 10% zeolite substituted mixture. Moreover, the limit value (4 MPa) required for use as roof support was obtained only for mixtures with 11% cement ??? 10% and 20% zeolite content. Generally, zeolite substitution seems to be more effective in early strength (up to 28th day). It has been determined that the long-term strength losses of zeolite-substituted paste backfill mixtures were caused by the reaction of sulfate and hydration products to form secondary gypsum, ettringite, and iron sulfate.