Multi-Factor Orthogonal Experiments and Enhancement Mechanisms of Unconfined Compressive Strength of Soda Residue Cement Lime Soil

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In order to study the effects of soda residue content, particle size, moisture content, and curing age on the unconfined compressive strength (UCS) of soda residue cement lime soil (SRCLS), a 4-factor, 4-level orthogonal experimental design was employed in this study. Different conditions of SRCLS UCS and their impacts were tested and analyzed. The internal microstructure and hydration products of SRCLS were studied using SEM and XRD to explore the strengthening mechanism of SR in SRCLS. The results indicate that as the soda residue content gradually increased, SRCLS UCS initially increased and then decreased, with a maximum increase of up to 67%. With increasing soda residue particle size and moisture content, the UCS of SRCLS gradually decreased. The optimized mix ratio was determined to be soda residue:cement:lime:soil = 3%:3%:6%:100%, with the soda residue dried naturally and an ideal particle size of 0.15 mm. The factors influencing the unconfined compressive strength (UCS) of SRCLS, in order of importance, are curing age, soda residue content, moisture content, and particle size of SR. Among these, curing age and soda residue content have a significant impact on the UCS. An adequate amount of SR can act as a fine aggregate filler, replace lime, promote cement hydration, and enhance chloride ion binding. This improves the grading of SRCLS materials and facilitates the formation of cementitious products from AFm, AFt, and Friedel’s salt, resulting in denser and stronger SRCLS materials. The research findings provide a reference for the mix design of SRCLS and the large-scale utilization of waste soda residue.