Abstract: The study aims to reduce soil and water loss in arsenic-bearing sandstone areas and promote the effective utilization of steel slag powder and arsenic-bearing sandstone in practical engineering applications. The effects of substitution rates and alkali equivalents of steel slag powder on the macro-mechanical properties and microstructure of arsenic-bearing sandstone-steel slag powder cement composite soil were investigated using unconfined compressive strength tests, X-ray diffraction (XRD), scanning electron microscopy, high-resolution three-dimensional microscopy and mercury intrusion porosimetry tests. Results show that under high-temperature alkali excitation, the gel and ettringite generated by the hydration of steel slag powder contribute less to the enhancement of composite soil than the cement does, which leads to a reduction in compressive strength of the composite soil with increasing substitution rate of steel slag powder. Increasing the dose of alkali activator promotes the generation of hydration products from steel slag powder, making it more effective in binding soil particles and filling internal pores. This results in a more uniform surface structure and a denser internal structure of the composite soil, which enhances its compressive strength. The best effect was observed when the alkali equivalent was 2%. The results provide a theoretical basis for the practical application of arsenic-bearing sandstone-steel slag powder cement composite soil in engineering.

Key words: steel slag powder, compressive strength, alkali equivalent, Arsenic-bearing sandstone, microstructure