A review of the suitability and performance of phosphogypsum as a material for road base and subbase construction

Abstract

Phosphogypsum (PG) use as a road base aggregate is gaining global interest as an alternative to resource-intensive stacking. Various methodologies, including utilizing PG alone, stabilizing with binders, or integrating with aggregates have been explored. This paper discusses these efforts, providing critical analysis and recommendations for PG use in road construction. Studies indicate that PG alone does not perform as an ideal road base material due to its uniform gradation, high solubility, low pH, and low bearing strengths (8–48 %) compared to traditional materials (80 %-200 %). Stabilization with cementitious materials like portland cement, fly ash, and lime can improve strengths and mitigate issues like shrinkage or swelling. Mixes with high PG content (>50 %) require additional aggregates, as cement content is typically limited to below 10 %, and several successful blends have been identified. Another approach involves incorporating common granular base materials which optimizes gradation and enhances bearing ratios to meet design specifications. Key parameters affecting material strengths include cement content, compaction, water content, and material pH. The opportunities and challenges encountered at pilot-scale studies are dated, and more research is required regarding the field behavior of modern techniques. Given evolving considerations for recyclability, expanding research on PG-amended road construction presents clear opportunities.