Các hạt silica fume cực kỳ nhỏ. Trung bình, các hạt khoảng 0.1 micromet (100 nano mét) đường kính. Để đặt điều này vào quan điểm, if a typical silica fume particle was the size of a football, then a single grain of cement would be about the size of a car.

The small particle size is a key reason why silica fume is so effective as a pozzolan in concrete. It fills in the gaps between larger particles, reducing the porosity and increasing the strength and durability of the finished product.