Utilisation of silica-rich waste in eco phosphogypsum-based cementitious materials: Strength, microstructure, thermodynamics and CO2 sequestration

Abstract

Phosphogypsum-based cementitious materials (PGCM) are commonly selected as substitutes to ordinary Portland cement (OPC), however, drawbacks, such as a restricted capacity for CO2 sequestration and reduced mechanical properties upon carbonation, limit the potential applications of PGCM. This study investigates the carbonation process mechanism of PGCM and explores to modify the hydration product classes of PGCM by using two silica-rich solid wastes, which are waste glass powder (WGP) and silica fume (SF). This innovative approach resulted in an improved carbon capture capacity and enhanced mechanical properties of PGCM. The addition of SF and WGP increased the compression strength of PGCM by 15.5% and 19.0%, respectively. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were utilized to investigate the hydration mechanism of PGCM supplemented with SF and WGP, in order to gain a comprehensive understanding of their properties. The addition of SF and WGP to PGCM resulted in a 9.9% and 21.6% increase in thermal conductivity, respectively. Furthermore, the addition of SF and WGP facilitated higher CO2 sequestration rates for PGCM (49.76% and 44.05%, respectively), while after carbonation, the strength loss rates were reduced to 16.8% and 13.35%, respectively. Finally, a simple sustainability analysis showed that the utilisation of silica-rich waste in PGCM has environmental sustainability benefits.