Investigation of utilization of alkali activated blast furnace slag as binder in paste backfill

In paste backfill (PB) of sulfide-rich mill tailings, strength losses and durability problems occur in the long term when ordinary Portland cement (OPC-CEM I 42,5R) is used as a sole binder. In this study, the utilization of alkali activated blast furnace slag (AAS) in order to produce durable PB from sulphide rich tailings against acid and sulphate attack was investigated. A total of 630 samples were prepared using OPC (for control) and, neutral and acidic blast furnace slags activated with liquid sodium silicate (LSS) and sodium hydroxide (NaOH). In studies; i) the effect of binder type and proportion at 5-6 and 7 wt.%, and at 7 wt.% constant binder proportion; ii) the effect of Na2O dosage of alkali activator at 6-8-10 wt.% of slag by weight, iii) the effect of modulus ratio (Ms) of LSS at 0,75-1,0-1,25-1,5-2,0 and, iv) the effect of slag fineness of 3150-4600-6000 cm2/g Blaine were investigated. The curing times were selected to be 14-25-56-112-224-360 days. PB samples prepared with AAS produced approximately 1.53 to 5.08 times higher 360-day strengths than those with OPC at binder dosages of 5-6 and 7 wt.%. AAS were found to have produced durable samples over 360 days of curing. A strength loss have been observed in the samples prepared from OPC due to acid and sulphate attack. However, those prepared from AAS samples were seen to be more resistant to acid and sulphate attack compared to OPC. According to the findings, alkali activated blast furnace slag at 8% Na2O dosage, at 4600 cm2/g blainess, at 1,0 Ms (for LSS) and at >6 wt.% binder proportion is seen to be essential for PB operations.