Effect of superplasticizer on the setting behaviors and mechanical properties of tailings-waste rock cemented paste backfills

Jinchuan Mine is facing the problem of a large number of tailings and waste rock, which forced the mine to establish tailings-waste rock cemented paste backfilling (TW-CPB) system. However, the transport ability and setting process of TW-CPB slurry have aroused the mine's attention, and adding appropriate superplasticizer is expected to be one of the options to solve this problem. This paper investigates four types of superplasticizers: Polycarboxylate- (PC-P), Naphthalene- (FDN), Aliphatic- (AK), Melamine- (SM), and five different contents: 0.5 %, 1.0 %,1.5 %, 2.0 %, 2.5 % (by mass of cements),tests the bleeding rate, setting time, internal water evolution, hydration products, and microstructure during the setting period, and assesses the unconfined compressive strength (UCS) of the TW-CPB samples at different curing times. Test results showed that the appropriate superplasticizers can effectively improve the water distribution in the slurry, which is conducive to the to slurry transportation in the initial process, promote the hydration reaction and change the morphology and microstructure of the main hydration products, which is important to the UCS improvement of TW-CPB sample. Finally, considering the effect on the fluidity and UCS, it can be concluded that the reasonable addition type and content of the superplasticizer in TW-CPB is 0.5 % of PC-P in the Jinchuan Mine. Furthermore, the successful application of superplasticizer of the TW-CPB would be significance to the utilization of tailings and waste rock.