Mechanical Properties and Mechanisms of a New Alkali-Activated Cementitious Material Compared to Ordinary Portland Cement–Solidified Saline Soil

The inherent deteriorative characteristics of saline soil limit its application as a backfill material in engineering practice. Achieving green, low-carbon disposal and resource utilization of saline soil has therefore become an urgent challenge. In this study, a sustainable alkali-activated cementitious material was developed using three typical industrial byproducts (IBP), i.e., iron tailings, fly ash, and ground granulated blast furnace slag as precursors, with lime and NaOH as composite activators, to stabilize saline soil and enhance its engineering performance. This multisource IBP system differs from previous studies that mainly relied on single or binary precursors and ordinary portland cement (OPC). The effects of curing agent (CA) content and curing time on the mechanical properties of stabilized soil were systematically investigated, and the curing mechanism was analyzed through X-ray diffraction and scanning electron microscope. The results indicate that with increasing CA content and curing time, the unconfined compressive strength, triaxial shear strength, California bearing ratio, cohesion, and internal friction angle of the stabilized saline soil were significantly improved, meeting the requirements of subgrade design specifications. Compared with untreated saline soil, the alkaline environment facilitated the breakdown of precursor bonds, releasing active [ SiO 4 ] − 4 and [ AlO 4 ] − 5 species, which promoted the formation of abundant C(N)─ A─ S─ H hydration products. These products encapsulated soil particles, filled pores, and enhanced interparticle bonding, thereby improving structural stability. The proposed process effectively utilizes IBP, reduces dependence on OPC, and offers substantial benefits in resource recycling and carbon reduction. This study provides theoretical and practical support for the green disposal of saline soil and sustainable infrastructure development.