Phosphogypsum recycling: New horizons for a more sustainable road material application

Abstract

It is aimed in this paper to suggest novel alternatives to recycle phosphogypsum (PG) in road applications. The performance of several formulations for the stabilization of raw PG with other selected materials was evaluated. The research began with a feasibility study of using raw phosphogypsum alone as embankment material, then focusing on the effect of stabilizers such as clayey soil (SM), fly ash (FA), lime (L), calcareous material (CM) and a special hydraulic road binder (HRB). The objective was to increase the strength up to a threshold favouring the use of the stabilized mix as a base material in road pavement, while ensuring a neutralization of acidity generated by PG. Environmental, mineralogical and geotechnical properties of raw materials were investigated. According to compressibility parameters, initial moisture content and compaction characteristics, this study confirms first that the use of PG alone should be limited to ordinary embankments of heights less than 4 m. Secondly, the mix PG:SM = 40:60 allows to use a significant amount of raw PG while maintaining good performances in terms of fractal behaviour of particles size distribution, immersion resistance, load bearing capacity and compaction characteristics. This mix has also successfully passed the compressibility risk under loading effect on the embankments. Finally, the compatibility of the mix (CM:PG:SM):HRB = (10:25:65):7 for the capping and pavement layers use was confirmed. TCLP method was carried out on the stabilized mix samples to verify the contamination risk.