Engineering properties and microscopic mechanism of phosphogypsum-rubber composite cemented soil

To address the low early strength, brittleness, and poor crack resistance of traditional cement-stabilized soil, this study proposed a novel phosphogypsum-rubber composite cemented soil material. The effects of phosphogypsum (PG) and rubber (R), alone and in combination, on compaction characteristics, unconfined compressive strength, and permeability of cemented soil were investigated. Additionally, the synergistic mechanism was further elucidated from a microscopic perspective through the combination of X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests. The comparative analysis indicated that the composite material outperforms the individual components in terms of strength, toughness, and impermeability, demonstrating a unique complementary effect. Specifically, at a cement content of 8%, the addition of 25%PG enhanced the early strength development and overall compressive strength, while the incorporation of 1%R-2%R effectively reduced the maximum dry density, improving toughness and impermeability. The microscopic observations disclosed that the formation of C-S-H gel and ettringite(AFt) played a critical role in improving the mechanical and durability properties. This study effectively addresses the limitations of traditional cement-stabilized soil, offering an innovative and sustainable strategy for reutilizing industrial solid waste, thereby promoting mechanical efficiency and environmental benefits.