Strength, Durability, and Microscopic Analysis of Silt Solidified with Two-Phase Phosphogypsum and Cement Fiber

The accumulation of silty soils and industrial solid waste not only results in a significant waste of land resources but also causes environmental pollution. Phosphogypsum and cement are commonly utilized as binding agents for the solidification of silt in engineering applications. However, the use of PG and cement alone may lead to issues such as insufficient strength, crack formation, and poor durability. Therefore, this research considered and employed a two-phase stabilization method using phosphogypsum and cement to solidify silt. Additionally, to further enhance the durability of the stabilized silt, polypropylene fiber (PP) and sodium sulfate (Na₂SO₄, NS) were incorporated. The effects of two-phase phosphogypsum and the proportion of hemihydrate phosphogypsum (BHPG) in the two-phase phosphogypsum on the strength characteristics of the stabilized silt were investigated through unconfined compressive strength tests and durability tests. The results show that when the content of two-phase phosphogypsum is 5%, and the proportion of BHPG in the two-phase phosphogypsum is 20%, the 28-day unconfined compressive strength of the stabilized silt reaches 1.42 MPa, and the deformation modulus is 95.5 MPa. After incorporating sodium sulfate (NS), the water and frost resistance of the stabilized silt significantly improved. The microstructural analysis shows that NS promotes the formation of ettringite. Furthermore, an excessively high proportion of hemihydrate phosphogypsum (BHPG) in the two-phase phosphogypsum content can lead to dihydrate phosphogypsum (2HPG) not being encapsulated by hydration products, which results in a less dense structure of the solidified silt and a decline in performance.