Effect of substitution of silica fume on the mechanical properties of cemented paste backfill

Abstract

Cemented paste backfill (CPB) contains 70-85% solids by total mass that is a mixture of process tailings, water (fresh and/or mine processed), and a hydraulic binder (often ordinary Portland cement). The purpose of this study is improving the strength of the cemented paste backfill, reducing quantities of mining tailings in the tailings storage area and lower binder cost. Also, the effect of Silica Fume (SD) was investigated on mechanical properties (Uniaxial compressive strength and Ultrasonic pulse velocity) of CPB. In the present study; mineral processing plant tailings were taken from the copper mine, Portland Cement (PC)(5%, 7% and 9% by weight), and water is mixed with taken from SD (5%, 10%, 15% and 20% by weight of cement) substitute for PC, CPB samples were obtained. Thus, using SD instead of PC was investigated the effect of on the mechanical properties of CPB. Obtained CPB samples were stored in a curing cabinet at 25°C and at least 80% humidity and subjected to uniaxial compressive strength (UCS) and ultrasonic P-pulse velocity (UPV, Pundit) tests at curing times of 3, 7, 14 and 28 days. The limit value of ? 4 MPa required for roof support is exceeded in all mixing (5%, 10%, 15% and 20% by weight) ratios in 9% cement. On the contrary, at 5% and 7% PC, the limit value does not exceed all mixture ratios (5%, 10%, 15% and 20% by weight SD). The maximum values of UCS at 28 curing period were obtained 10 wt. % SD- 9% cement (6.28 MPa). This value showed a strength of 3 times in the 28 day cure period according to the reference cemented samples (only 9% portland cement). Ultrasonic pulse velocity of cemented paste backfill showed the similar trend with UCS. Consequently, an additive of %10 SD directly has affected the cost of CPB due to reduces the cement ratio (%10 ratio). Copyright © 2020 by SME