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Experimental study on durability of fly ash based filler slurry under different sulfate concentration

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Document pages: 12 pages

Abstract: In order to study the effect of different concentrations of sulfate on the strength of fly ash based coal mine filling paste, the change of uniaxial compressive strength of filling paste soaked in different concentrations of sodium sulfate solution for different times was studied by means of variable control and mechanical analysis, and its stress-strain curve was discussed. The hydration products of each block at different stages were analyzed by XRD. The results show that the effects of different concentrations of sodium sulfate solution soaking for different times on the strength of filling body are different. The sodium sulfate solution with the concentration of 5 can activate the fly ash based filler slurry and improve the strength of the filler slurryth of the filling paste. A sodium sulfate solution with a concentration of 10 and 15 increased the early strength of the paste test block faster, but after 60 d, the strength decreased. The stress-strain curves for these blocks show that the elastic moduli of the filling paste test blocks change irregularly, and it was found that with the increase in soaking time, the blocks soaked in the 10 and 15 sodium sulfate solutions developed fissures in the later stage that adversely affected the strength of the filling paste. The XRD results show that the filling paste test block hydration products are hydrated calcium silicate (C-S-H) based and that ettringite (AFt), beneficial to strength of the filling paste in proper quantities, appeared in the main product of the filling paste test blocks that were soaked in the sodium sulfate solution. With the increase in the concentration of the sodium sulfate solution, the AFt is generated in larger quantities, and gypsum crystals begin to appear, which is not conducive to the filling paste block strength.

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