Analysis of mechanical properties and microstructural mechanisms of curing agent-stabilized phosphogypsum road base materials and their engineering application

• Efficient resource utilization of industrial solid waste phosphogypsum. • Revealed the mechanism of action of curing agent and established macro-micro performance correlation. • Pass engineering verification and conduct environmental assessment, and have engineering promotion value. This study aims to recycle phosphogypsum as a road base material. The study uses phosphogypsum as the main material, a laboratory-made curing agent as the gelling agent, and a high-polymer dispersant as an admixture to explore the properties of phosphogypsum road base materials. The hydration mechanism and microstructure of the composite material were characterized by XRD, SEM and MIP test, and engineering application and environmental assessment were carried out.The results show that: The compressive strength of phosphogypsum base material under dry curing is higher than that under standard curing. Long-term humid environment will inhibit its strength growth. The compressive strength of the material increases with the increase of curing agent content. Under dry curing conditions, the unconfined compressive strength of the mixture with 13 % curing agent (C-13) reached 5.55 MPa after 7 days. The strength was increased by 12.61 % after further adding 0.3 % dispersant (C13-DA0.3) after 7 days. The material expands first and then decreases during the drying and curing process. The addition of polymer dispersant can effectively reduce the expansion. The expansion strain of C13-DA0.3 is finally stabilized at 419 × 10 –6 . MIP analysis showed that at 7 days, the proportion of small capillaries in C13-DA0.3 increased by 11.76 % compared with C-13, which was consistent with the change law of mechanical properties. XRD and SEM analysis showed that the main hydration products were C-S-H gel, ettringite and a large amount of unreacted dihydrate gypsum. The unconfined compressive strength of the on-site core C-13 sample reached 4.3 MPa after 7 days.