silica fume, or called microsilica, is a by-product of silicon metal production.
In high temperature,some sio2 become a gas and float . Factory then gather these sio2 with special facility.
That's the way micosilica comes.
silica fume has high surface activity can use in cement. silica fume can improve the strength of concrete and reduce quantity of cement .
So silica fume bring you more profit in construction.