Role of silica fume in CFBFA-GGBS geopolymer grouting material: Multi-property optimization and freeze-thaw degradation mechanisms

Abstract

This study systematically investigates the gradient effects of silica fume (SF) dosage on the mechanical performance and microstructure of CFBFA-GGBS-based geopolymer grouting material. The structure-performance relationships were elucidated through rheological, workability, and mechanical tests, coupled with multi-scale techniques including XRD, FTIR, SEM, EDS, and LF-NMR. The results demonstrate that optimal SF incorporation enhances rheological behavior and workability through synergistic physicochemical interactions. Specifically, an SF dosage of 8% improves fluidity by reducing inter-particle friction via the ball-bearing effect of spherical SF particles. Nano-sized particles reduce pore connectivity through physical filling, while reactive silica accelerates C-(A)-S-H gel formation and densification via secondary pozzolanic reactions. However, excessive SF disrupts hydration kinetic equilibrium, inducing localized defects in the gel network. The optimal SF dosage for balanced workability and mechanical performance is 12%, which enhances both fluidity and compressive strength. Microstructural analyses reveal SF-induced nucleation effects driving the development of nano-structured gel phases, with multiscale structural reorganization significantly improving mechanical performance and durability. This work innovatively clarifies the “filling-catalytic-reconstruction” mechanism of SF in geopolymer systems, advancing theoretical frameworks for optimizing industrial solid waste-based grouting materials. These findings provide critical insights for proportion design and engineering applications of CFBFA-GGBS-based geopolymer grouting material.

Keywords

silica fume / circulating fluidized bed fly ash / ground granulated blast-furnace slag / geopolymer grouting material / performance / microstructure

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