Abstract: Pumping agent has been widely used in mines as an additive to improve the fluidity of slurry， but the effect of pumping agent on filling body mechanical properties is not clear. For this reason， the slurry slump and rheological of filling slurry， and the uniaxial compressive strength and microscopic structure of the filling body with different pumping agent dosage were tested. The results show that the pumping agent has a nonlinear gradient effect on the slump. With the increasing of pumping agent dosage， the influence of the same dosage on the slump is gradually weakened. Both the yield stress and the plastic viscosity decrease with the increasing of the pumping agent dosage. The drop of the yield stress is obviously slowed down after the pumping agent dosage exceeds 3%. For the plastic viscosity， when the dosage exceeds 2%， the decrease rate has begun to slow down significantly. The effect of pumping agent on the filling body strength at 3 d age is inconspicuous. For 7 d and 28 d age strength， the effect is positive when the dosage is 1% and 2%， but it is negative when more than 2%. When the dosage is 1%， the microstructure of the sample is the most compact. As the pumping agent dosage increases， the macro voids gradually increase.Considering the pumping agent cost， the slurry fluidity， and the filling body compressive strength， for the ratio of the slurry in the test， the recommended dosage of the pumping agent is 2%.

Key words: filling mining, pumping agent, fluidity, compressive strength, microstructure