Experimental research on the application of alkali residue-based lightweight soil subgrade filling

Alkali residue (AR) is a waste byproduct generated during the soda production process using the ammonia alkali method, leading to significant environmental pollution in soil, air, and water as a result of its extensive accumulation. The proposed technology and method for producing alkali residue lightweight soil (A-LS) with AR was designed to facilitate the efficient reuse of AR. The method's feasibility was substantiated through indoor trials and field-filling tests. This study involved an experimental analysis to determine the material proportion and preparation method for A-LS. Compressive strength tests, shear tests, CBR tests, dry-wet cycle tests, freeze-thaw cycle tests, and field filling tests were conducted to investigate the mechanical properties, durability, and road performance of A-LS. The findings demonstrate that the compressive strength, secant modulus, shear strength, and CBR increase with the increase of wet density. These properties exhibit an upward trend with the extension of age. A-LS exhibits remarkable resistance to dry-wet and freeze-thaw cycles, boasting excellent durability. A-LS was applied to the X204 bridgehead of Xuwei-Guanyun section of Lianyungang-Suqian expressway. The field-filling tests demonstrate that A-LS meets the design and specification requirements in terms of compressive strength, CBR, resilient modulus, and deflection. A-LS demonstrates exceptional capacity to absorb significant quantities of AR waste, resulting in a remarkable 70% reduction in the usage of ordinary Portland cement. This substantial reduction in ordinary Portland cement signifies a substantial decrease in carbon emissions. A-LS boasts several noteworthy attributes, encompassing simple process, economic and environmental protection, adjustable density and strength, and wide application range. A-LS exhibits a good application prospect.