Cement-phosphogypsum stabilized aggregate interlocking road base material: preparation, application and environmental impact

For the extensive and cost-effective utilization of phosphogypsum in highway engineering, a cement-phosphogypsum stabilized coarse aggregate interlocking road base material is developed in this study. The influence of aggregate gradation and phosphogypsum replacement for fine aggregate on the maximum dry density, optimum water content, unconfined compressive strength, water stability and drying shrinkage of the cement-phosphogypsum stabilized aggregate is investigated. Appropriate coarse aggregate content improves maximum dry density, and the formation of an aggregate interlocking framework is beneficial to unconfined compressive strength. The incorporation of phosphogypsum further enhances the strength development, water stability and volume stability of cement-PG stabilized aggregate thanks to its filling and hydration effects. By incorporating phosphogypsum, the required cement dosage can be reduced by at least 20% (e.g., from 5.0% to 4.0% by weight of aggregate) while maintaining an unconfined compressive strength comparable to that of traditional cement-stabilized aggregate. Cement-phosphogypsum stabilized aggregate interlocking road base material is produced and successfully applied in highway construction. The road base exhibits qualified compactness, planeness, thickness and profile elevation, and its core sample presents a denser structure than that of the traditional cement stabilized aggregate road base. Compared with the traditional cement stabilized road base, the raw material cost of cement-phosphogypsum stabilized aggregate interlocking road base can be reduced by 14.4%, while achieving comprehensive utilization of a large amount of phosphogypsum and posing no significant environmental pollution risk. The cement-phosphogypsum-stabilized aggregate interlocking road base material has wide application prospects in highway engineering.