Preparation And Properties Of Slurry Expansion Filling Materials

In order to solve the problems of low early strength and low rate of supporting pit roof of cemented paste backfilling(CPB)with low-concentration tailings,the optimal binder mixing ratio was obtained and a new type of CPB with low cost and high early strength was prepared in this paper through the mixture design based on the components of slag powder,reinforcing agent and desulfurized gypsum.The influence of different water reducing agent and activator on the fluidity and strength of the new type of CPB was studied.Based on the previous research,a new kind of expansive agent with low cost was used to prepare the slurry expansion filling material,which has high expansion rate and low loss of stenghth.The influence of expansive agent on the structure and properties of CPB was studied,and the reasonable content of expansive agent under different conditions was determined.Research results indicate that:(1)The optimal binder mixing ratio is: 22.5% reinforcing agent,12.5% gypsum and 65.0% slag powder.The 3d,7d and 28 d strength of the CPB was 0.71 MPa,1.20 MPa and 2.11 MPa respectively when binder to tailing ratio is 1:8.The main factors that affect the 3d and 7d strength of the CPB are the amount of reinforcing agent and slag powder,and gypsum is the most significant factor that affects the 28 d strength.(2)The results of XRD and SEM analysis indicate that the main hydration products of the new cementitious material are AFt crystal and C-S-H gel.The network structure formed by AFt and C-S-H gel is the main source of strength growth of the CPB.(3)Water reducing agent can effectively improve the fluidity of filling slurry,and the improvement effect is related to the type and amount of water reducing agent.FDN can improve the fluidity of filling slurry more effectively compared with SMF and Polycarboxylate Superplasticizer.The flow expansion of the filling slurry reaches 139 mm when FDN content is 2.0%,which is 23.0% higher than that without FDN.(4)The strength of the CPB can be improved by using activator and the effect is different with different kinds and dosages of activators.Activator can significantly increase the strength of CPB at different ages.The strength of CPB at 3d,7d and 28 d can reach at 0.77 MPa,1.53 MP,2.44 MPa under the optimal dosage of 3%,which is significantly improved by 18.5%,24.8%,and 35.6% respectively compared with that of the blank group.(5)The expansion of slurry can be effectively controlled by adding expansive agent to realize compact roof-contacted filling and the expansion rate can be controlled by the dosage The strength of the CPB decreases with the increase of expansion rate and the requirements of expansion and strength properties of the CPB could be met at the same time with reasonable binder to tailing ratio and the amount of expansive agent.When the binder to tailing ratio is 1:4 and the content of expansive agent is 0.16%,the CPB has a high expansion rate of 17.04% and its strength at the age of 3d,7d,and 28 d was 0.70 MPa,1.61 MPa and 2.07 MPa,which meets the requirements of supporting pit roof.(6)A large number of small pores with uniform distribution can be produced in the CPB with proper dosage of expansion agent.The formation of this kind of pore structure not only ensures the ideal expansion,but also reduces the loss of strength in different age of the CPB.