Influence of trace chemical constituents in phosphogypsum for road base applications: A review

The use of phosphogypsum as an amendment to graded aggregate road base serves as an alternative to traditional and recycled aggregate sources. This provides a solution to issues currently faced by the phosphoric acid industry due to limited recycling opportunities, aggravated by a lack of understanding of variability in phosphogypsum due to source, location, and process worldwide. This manuscript provides a comprehensive overview of the chemical differences in phosphogypsum from around the globe and discusses the opportunities and challenges associated with phosphogypsum-amended road bases. The literature reveals that although mineralogical composition between sources remains similar (calcium sulfate), the total and leachable constituent concentrations vary significantly between facilities worldwide, impacting applicability and behavior as a road base material. Different approaches include using phosphogypsum as a base material alone, blended with aggregate, or stabilized and several studies report physical and environmental success, although thorough environmental monitoring of pilot-scale risk is lacking.