Application of Raman Spectroscopy for Tracing the Status of Silica Fume in Cementitious Materials

Silica fume (SF) is an important component for manufacturing high performance concrete (HPC), owing to its superb pozzolanic reactivity and physical filling effects. However, application of SF in concrete may cause potential hazards issues. Although using SF in slurry form can somehow reduce the potential biotoxicity, the long-term stability and status of the SF particles within cementitious materials is still uncertain. In the current study, attempts were made to use Raman spectroscopy as an innovative alternative technique for tracing and identifying the status of SF both in its original SF slurry and in a 6-month-old hydrated cement paste. Light-optical microscope was also used to examine the morphology of the SF particles in the aforementioned samples. The results showed that under Raman spectroscopy, the various components of the SF in slurry, such as amorphous silica, silicon crystal, and carbon, were clearly recognised. In addition, the SF agglomerates formed in the slurry were also detected. On the other hand, the chemical composition, status, and morphology of both SF and SF agglomerates in the 6-month-old paste were also identified. The study reported in this paper indicates that Raman spectroscopy could be a potential technique for tracing the status of SF, so that the potential safety hazards of SF can be monitored.