Study On The Self Flow Slag-based Tailing Backfilling Materials

The classified tailings backfill slurry that had cement-sand ratio of 1:10 and solid concentration o f 68% was prepared by classified tailings and outsourcing binders in the mine. There were a series of problems, such as slow condensation, low compressive strength, high cost, when backfilling slurry was used to achieve gravity-flow backfilling. So it was necessary to optimize the formula of backfilling material.In this paper, the effects o f activators including cement, hemi-hydrate gypsum(HG), dihydrate gypsum(DG) and quicklime on the performance of slag-based tailings backfill materials were studied by single factor experiment with using slag as raw backfilling cemented materials. Results showed that, slag-based tailings backfill materials activated by single cement had long setting time and low compressive strengths. The backfill material adding HG had shorter setting time and higher the rate o f supporting pit roof, but its fluidity and the long-term strength were reduced. The fluidity and early strength o f material with extra DG were improved. However, effect o f additional DG on long-term strength was low. The backfill material adding quicklime had high later strength and long setting time. As a result, it was necessary to develop the desired gravity-flow slag-based tailings backfill material was by a synergy mechanism of activators above.Orthogonal design and test selected the gypsum contents, the ratio of HG and DG and quicklime contents as the factors with fixed cement content of 15%, in order to get the best proportion of the binders of slag-based tailings backfill materials. Based on the orthogonal experiment, this study optimized the proportion of binder only by changing the ratio of cement and gypsum and result showed that slag-based tailings backfill material without cement was feasible, but had disadvantage on early strength. So thispaper studied separately adding four types of chemical activators including Na OH, Na2Si?3, Na2S?4 and Al2(S?4)3, to improve the strength. The results showed that and the optimal activator was the Al2(S?4)3 with the content of 1 ?0%. The proportion of the binder o f non-cement slag-based tailings backfill material was slag71.0%, HG8.3%, DG16.7%, lime3.0% and Al2(S?4)31.0%. Compared with the original backfill material, non-cement slag-based tailings backfill material had better fluidity, and reduced the setting time by 19.4, the strength of 3d, 7d and28 d separately increased by 32.1%, 12.9%, 16.3%.This paper studied the effect o f three types of superplasticizers, including naphthalene-based superplasticizer(FDN), aminosulfonic acid-based superplasticizer(ASF), polycarboxylic superplasticizer(PC), on the non-cement slag-based tailings backfill material while increased the solid concentration from 68% to 72%. The result showed that the advisable addition of superplasticizers effectively improved the fluidity, and the tailings backfill slurry could be satisfied under 72% concentration gravity filling with the content o f FDN, ASF and PC were 0.7%, 0.27% and 0.38%. The addition of superplasticizers increased the bleeding rates and extended the setting time, yet the unfavourable influence of ASF was the minimum. Adding FDN could decrease the 3d strength, while adding ASF and PC increased 3d strength to a certain degree. As the increase of curing age, these three types of superplasticizers had advantages on late strength. On the whole, it was determined to use ASF0.27% in the developed non cement slag-based tailings backfill material. The final proportion of the self flow slag-based tailings backfill material was cement-sand ratio of 1:10 and solid concentration of 72% with the binder o f non-cement slag-based tailings backfill materials and ASF 0.27%. Compared with the original backfill material, the solid concentration increased by 5.9%, and the bleeding rate and setting time reduced by 30.1%andl9.4, the strength of 3d, 7d and28 d separately increased58.9%> 39.5% and 47.3%?.Using XRD and SEM to observe and analysis the hydration products of non-cement slag-based tailings backfill material, It was found that the main hydration products were C-S-H and Aft crystals, which wrapped in tailings particle surface, or filled between the tailings particles, shaping the space network structure andcross-linked with each other, that could promote the formation of strength.