Research On The Controllable And Low Strength Paste Filling Material

It is reported that the annual dumped mining tailing is more than 5 billion tons in the world,and the total storage of tailing has exceed 6 billion tons in China.The tailings production in China was nearly 960 million tons in 2015,accounting for 30.7% of the total solid waste,while the comprehensive utilization rate was only 28.5%.Billions of tons of tailings piled up on ground,occuping farmland and even causing the tailings dam break accident,and thus led to a series of ecological and environmental problems such as soil pollution and river pollution.Therefore,the paste filling has become a major issue commonly concerned in the world.In this study,the goldmine tailings from Luquang,a district of Shijiazhuang,are selected as the raw material.The first section is using the chemical activator,i.e.sodium hydroxide,sodium carbonate,sodium silicate,calcium hydroxide,calcium sulfate,cement clinker,sodium sulfate,potassium sulfate,potassium carbonate,twelve water aluminium potassium sulfate,aluminum sulfate,sodium chloride,sodium nitrate,sodium nitrite,sodium chloride,triethanolamine and sodium thiosulfate,to activate the activity of slag.Based on the multilevel contrast test,according to the 28 d compressive strength and the market price of each activator,several excellent activators are determined.Then the selected activators are recombined using the orthogonal design,and the composition of compound activator are obtained considering the flowability,7 d strength and 28 d strength.Results indicate that the optimum activators are sodium chloride,aluminium sulfate,triethanolamine,calcium oxide,calcium sulfate and cement clinker,and its proportion is 1 : 4 : 5 : 5 : 24,respectively.The second section is using the orthogonal design to determine the composition of the new cementitious materials containing ground slag,compound activator,steel slag and fly ash.Result shows that the content of ground slag,steel slag,fly ash and compound activator are 571.4 g/kg,142.9 g/kg,142.9 g/kg and 142.9 g/kg,respectively.Testing different concentration and paste benchmark contrast new cementing materials and cement compressive strength,fluidity and slump,new type cementing material has good workability,strength of 28 d can achieve a minimum of 2 MPa.By observing the microstructure and XRD of sclerotium new hydration products that have AFt and AFm,and calcium hydroxide and C-S-H,etc.