Tracing the status of silica fume in cementitious materials with Raman microscope

Silica fume (SF) is an essential material for formulating high performance concrete (HPC). However, its small particle size could cause safety-hazards. Although replacing SF powder with slurry can somehow avoid the potential bio-toxicity, its long-term stability within cementitious materials is unknown. In this study, Raman microscope which combines Raman spectroscopy with light-optical microscope was successfully applied to characterise the composition and morphology of SF in original slurry and hydrated SF-Portland cement (PC) pastes. The unhydrated SF-agglomerates were clearly detected in the original SF slurry and the 22-hour and 6-month hydrated SF-PC pastes.