What does this research mean for the field?

Silica fume-modified phosphogypsum-based cementitious material enhances compressive strength by 63% and reduces water absorption by 48% compared to the control mix. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.NEUTRAL.

What question did this study set out to answer?

The research aims to improve the mechanical properties and water resistance of phosphogypsum-based cement through the addition of silica fume and other materials.

March 6, 2026Open Access

Valorization of phosphogypsum and silica fume in sustainable cementitious materials: Multi-objective optimization and mechanistic insights

Puntos clave

The research aims to improve the mechanical properties and water resistance of phosphogypsum-based cement through the addition of silica fume and other materials.
Developed a silica fume-modified phosphogypsum-based cementitious material (SF-PCMS) using waste materials.
Employed Response Surface Methodology (RSM) for multi-objective optimization of mix proportions.
Evaluated mechanical properties using tests for compressive strength, water absorption, and softening coefficient.
Achieved a compressive strength increase from 21.75 to 35.53 MPa with the optimized mix.
Reduced saturated water absorption from 16.23% to 8.48%.
Improved the 7-day softening coefficient from 0.66 to 0.81.

Resumen

The massive global stockpile of phosphogypsum (PG), an industrial solid waste, exceeds 6 billion tons and continues to grow, posing significant ecological risks due to land occupation and contaminant leaching. To address these challenges, overcome the poor mechanical strength and water resistance of β-hemihydrate phosphogypsum (β-HPG), this study developed a novel silica fume-modified phosphogypsum-based cementitious material (SF-PCMS) using industrial solid wastes. Silica fume (SF, micro-filler/pozzolan) was introduced in synergy with ground granulated blast furnace slag (GGBS) and carbide slag (CS, CaO-rich alkaline activator) to enhance mechanical strength and water resistance, evaluated by compressive strength, water absorption, and the softening coefficient. Given the complex interactions in this multi-component system, Response Surface Methodology (RSM) was employed to optimize the mix proportions, establishing high-precision predictive models (R2 > 0.97) for 28-day compressive strength, saturated water absorption, and the 7-day softening coefficient. Multi-objective optimization yielded the optimal mix (GGBS:CS:SF:β-HPG = 20:16.69:10:53.31; error <4%). Compared with the SF-free control (M15), MY increased compressive strength from 21.75 to 35.53 MPa while reducing saturated water absorption from 16.23% to 8.48% and improving the 7-day softening coefficient from 0.66 to 0.81. Furthermore, XRD and SEM analyses revealed that SF enhances performance through a triple mechanism: physical filling by its micro-fine particles, activation of hydration reactivity promoting the formation of structurally reinforcing C-(A)-S-H gel, and regulation of ettringite (AFt) formation. This study provides a viable pathway for the high-value utilization of PG through performance-oriented mix optimization and mechanistic understanding of silica fume in solid-waste-based binders.

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