Rheological characterization of cemented paste backfills containing superabsorbent polymers (SAPs)

The addition of superabsorbent polymers (SAP) to cemented paste backfill (CPB) made from tailings slurries may offer a good alternative to the dewatering components of the conventional CPB production owing to their highwater absorption and retention capacities. Therefore, an experimental program was implemented to characterize the rheological behavior of CPB incorporating an SAP. Two types of binder comprising a general use Portland cement (GU) and a blended binder (GUSL) consisting of 80% ground granulated blast furnace slag (GGBFS) and 20% GU were used. Two different binder proportions, B-w (=100 x M-binder/Mdry-tailings) of 4.5 and 7% were tested. An SAP dosage (ratio of the dry mass of SAP to the volume of the tailings slurry) of 30 and 34 kg/m(3) was assessed in this study. Results showed that the SAP addition distinctly reduced the yield stress (tau(0)) and the infinite shear viscosity (mu proportional to) and increased the small cone (H = 150 mm) slump height (s) of such mixtures over time. Moreover, The SAP-thickened tailings CPB (SAP-TT CPB) showed a severe shear-thinning behavior marked by a negative flow index (n < 0) and moderate to extremely low yield stress (tau(0) in the range 21-78 Pa), while the corresponding reference CPB without SAP added (Ref) exhibited a normal shear-thinning behavior with moderate to slightly high yield stress (tau(0) in the range 76-206 Pa).