Mechanical Characteristics and Micro-Mechanism of Modified Dredged Sludge Based on Calcium-Containing Solid Waste Used as Landfill Cover Materials

In order to prepare a new type of landfill covering material for closure, we used industrial calcium-containing waste (construction rubbish, slag, desulfurized gypsum and fly ash) modify the dredged urban sludge. Shrink, unconfined compression, shear infiltration tests were performed obtain volume shrinkage, compressive strength, strength permeability coefficient modified sludge, as well under action wet dry cycles. Comprehensive characterization sludge using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy with energy dispersive spectroscopy detection methods, resulted in hydration products, molecular groups microstructure characteristics revealed modification mechanism After natural curing 28 d, shrinkage rate sample was 2.6~8.3%, 7.9~14.5 MPa, cohesion force c 179~329 kPa, internal friction angle ? 42.59~53.60°. six cycles, there no cracks sludge; reached stability at 0.84–11.1 × 10?7 cm/s; MS7 less than 1 cm/s, which met engineering anti-seepage requirements closure cover. The by alkali formed C–S–H C–A–S–H gelled geopolymer, filled gaps between soil particles form strong cement skeleton. Therefore, mix ratio sludge:construction waste:slag:fly ash:desulfurized 50:22:15:8:5. Calcium-containing solid can be cover closure.