The Design and Characterization of an Artificial Soil Substrate Made from Sand-Washing Slurry

The global reserve of sand has significantly decreased, and sand washing is predominantly favored due to its simplicity and low operational costs, but this method poses significant environmental risks like landslides, making its reuse essential for sustainability. In view of this challenge, based on the composite preparation method, an innovative approach was proposed to prepare an artificial soil substrate from sand-washing slurry. The physical and vegetative feasibility performance, including strength, density, water absorption, retention, electrical conductivity (EC), and pH; and microstructural characteristics, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR) of the artificial soil substrate with different proportions of cement and foaming agent were measured. Increasing the cement content to 30% of un-crushed artificial soil substrate specimens improved strength, whereas 40% reduced it due to the diminished pore-filling effect. Water absorption rates ranged from 29.22% to 36.68%, increasing with more foaming agent and decreasing with more cement, while the water retention time was 12–14 days, and incorporating foaming agent significantly increased water absorption. Leachate pH ranged from 11.99 to 12.18, and reduced to 7.82–8.28 with 5% phosphoric acid. The EC of the artificial soil substrate decreased by 88.64% to 93.59% after 10 wet–dry cycles, aligning with the standard. Artificial-soil-substrate-predominant products include calcite, quartz, and dolomite, with a pronounced silica content and soil substrate porosity ranging from 27.96% to 51.80%. From the microstructural test, calcium silicate hydrate gel, produced by cement hydration, effectively bound the sand-washing slurry, thereby improving strength.