... of the concrete contractor. Silica fume consists primarily of amorphous (non-crystalline) silicon dioxide (SiO2). The individual particles are ... particles, large surface area, and the high SiO2 content, silica fume is a very reactive pozzolan when used in ... erosion resistance is very demanding, micro-dopted silica fume is necessary. Microsilica fume has strong activity, a caustic water properties ...