Mechanical properties of phosphogypsum-soil stabilized by lime activated ground granulated blast-furnace slag

A large amount of phosphogypsum (PG, a solid waste) has been produced with the development of the industry. Activated ground granulated blast-furnace slag (GGBS) has been considered an effective solution for stabilizing PG in road construction. However, the mechanical properties of PG stabilized by lime-activated GGBS are not understood. This study attempted to mix PG and soil to make a PG-soil, and lime-activated GGBS was used as a treatment agent. The compaction test and unconfined compression strength test were conducted to investigate the mechanical properties of the specimens. A fatigue testing system was used to analyze the dynamic elastic properties of lime-GGBS stabilized PG. X-ray diffraction and scanning electron microscopy were used to study their mineralogy and microstructure. The results showed that the strength increase of stabilized specimens containing PG was 239.49% when the ratio of lime and GGBS (wt%) was 1:9 (the lime content was 1.5% of PG dry weight), compared to stabilized PG-free specimens. Under the same stress peak, the dynamic elastic modulus of the stabilized specimens containing PG was increased by 48.68% compared to stabilized PG-free specimens. Under higher stress peaks, the stabilized specimen without PG failed, whereas those containing PG merely experienced a decrease in dynamic elastic modulus. As the content of PG increased, more ettringite was generated. Additionally, the lime-activated-GGBS binder removed P and F impurities from PG. The results of this study can provide a reference for utilizing PG as a filling material for the embankment.