Because of its fine particles, large surface area, and the high SiO2 content, silica fume is a ... ,000sqm/kg, and it has extremely strong surface active. Because of its fine particles, large surface area, and the high SiO2 content, silica ... , 1.60 H2O (when bagged): 0.8, 0.40 Specific surface area (B.E.T.): 18sqm/g, 19sqm/g Bulk density ...