Silica fume is a byproduct of producing silicon metal or ferrosilicon alloys. Due to its physical and chemical properties, silica fume is a very reactive synthetic pozzolan. Concrete containing silica fume generates high strength and durability. Silica fume remains inert until water and Portland cement start hydrating when the chemical reaction produces two compounds Calcium Silicate Hydrate (CSH), which is the strength producing crystallization, and Calcium Hydroxide (CH), which acts as a pore filler.  The advantages of silica fume in concrete are:

• High durability
• Efficient finishing process
• High early compressive strength
• High flexural strength and modulus of elasticity
• Prevention of thermally induced cracking