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 concentra-tions vary significantly between facilities worldwide, impacting applicability and behavior as a road base ma-terial. 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.