The Effects of Seawater on the Dissolution Potential of Phosphogypsum:Cement Composites

Abstract

ABSTRACT Polarized optical microscopy, scanning electron microscopy, and X-ray microprobe analysis were used to investigate the effect of sea water on phosphogypsum (PG):cement composites. Thin surface sections were taken from 85%: 15% PG:cement composites that had been submerged under natural seawater conditions for 1 month and 70%:30% PG:cement composites that had been submerged under natural seawater conditions for 1 year. The optical microscopy results revealed a crystalline layer of carbonates on the surface of the 70%:30% composites, which was absent on the 85%:15% composites. Microprobe analyses indicated that the carbonates, in the form of CaCO3, were formed from Ca2+ and CO32− contained in the seawater, not from the composites. This CaCO3 coating may act as a physical barrier to seawater intrusion into the composites, preventing block degradation. The polarized optical and scanning electron microscopy images of the 85%:15% composites showed surface disruption, which is hypothesized to be caused b...