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Abstract
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Abstract: Recycled sand from construction waste presents a promising substitute for natural sand. However, such sand typically exhibits low strength, high crushing index, and poor grading. These characteristics render the recycled sand unsuitable in subgrade engineering involving cyclic shear stresses induced by wave, seismic and traffic loadings. This study investigates the application of Soybean Urease-Induced Calcium Carbonate Precipitation (SICP) method to enhance the engineering properties of recycled sands. Firstly, a number of factors influencing the precipitation process are examined, including soybean powder concentration, cementation solution concentration and the ratio between urea and calcium chloride. Subsequently, unconfined compressive tests are conducted on sands reinforced under various conditions. Results indicate that sample strength increases significantly with higher cementation solution concentration and grouting frequency. The strength demonstrates correlation with the amount of calcium carbonate formed during precipitation. Scanning electron microscopy reveals that the reinforcing effect can be attributed to calcium carbonate crystals formed between particles, which function as binding agents for the recycled sands
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