Study on mix proportion and mechanism of fine-grained tailing composite anti-seepage material

Traditional cement-bentonite cutoff materials suffer weak chemical corrosion resistance, and existing tailing-based barriers mostly take tailing as auxiliary filler, lacking multi-component synergistic modification with fine full tailing as primary aggregate. This study prepares a composite anti-seepage material with full fine tailing as main aggregate mixed with Portland cement, sodium bentonite and sodium silicate. Single-factor controlled variable tests with six groups of specimens were carried out to adjust cement and bentonite dosages; permeability tests, quadruple direct shear tests and Micro-CT scanning were conducted to test hydraulic-mechanical properties and micro-pore structure.Results showed that raw tailing possessed a permeability coefficient of 5.3 × 10 ₋4 cm/s while modified samples range from 1.1 × 10 ₋ ⁷ to 5.5 × 10 ₋ ⁷ cm/s. With bentonite fixed at 8 kg, increasing cement dosage raises permeability but greatly lifts shear strength: cohesion rises from 63.2 kPa to 345.2 kPa and internal friction angle grows from 30.2° to 39.1°. With cement fixed at 20 kg, rising bentonite content continuously reduces permeability to 1.1 × 10 ₋ ⁷ cm/s and slightly improves strength to 182.2 kPa cohesion and 38.9° friction angle. CT results prove the optimal specimen only has 1.94% porosity, controlled by cement hydration C-S-H gel cementation and bentonite swelling pore-blocking. This material realizes large-scale tailing recycling, fills the research gap of tailing-dominated composite barriers, and provides technical support for tailing pond vertical anti-seepage engineering with remarkable environmental and economic benefits.