Silica fume, also known as microsilica, it is essentially a by-product of the ferrosilicon industry. It is a highly pozzolanic material and is used to enhance the mechanical and durable properties of concrete. It can be added directly to concrete as an individual ingredient or by blending it with portland cement to produce high-strength concrete.
It acts as both a filler and a pozzolan. As a filler, it improves the physical structure by occupying the spaces between the cement particles. Silica fume acts chemically as a pozzolan and strengthens the concrete, making it more durable.
Silica fume has chemical and physical properties. It has fine particles, a large surface area, and is comprised of high SiO2 content. Therefore, it is a very reactive pozzolan.
Concrete containing silica fume has very high strength and is, therefore, durable. Studies indicate that the addition of silica fume to cement improves the durability of water impermeability and the carbonation resistance of the concrete. Adding silica fume to concrete also gives the concrete greater resistance to chloride penetration. Such concrete can be used in building parking structures, bridges, and bridge decks.
Silica fume has different applications. Because of its high reactivity as a pozzolanic material, it is used to make high-strength concrete. This concrete gives architects and engineers greater design flexibility.
Concrete enhanced with silica fume is used to construct long-lasting highway bridges, parking decks, marine structures, and bridge deck overlays.
Silica fume contains 85% to 99% SiO2. It's the main component of silica fume.
When you add silica fume to concrete, at first, it seems inactive. However, after adding Portland cement and water to the mix, they all begin to react with each other. The primary chemical reactions will produce two chemical compounds.
The first is Calcium Silicate Hydrate (CSH), which is the strength producing crystallization. The second is Calcium Hydroxide (CH), which is a by-product also called free lime. The latter is responsible for lining available pores within the concrete as a filler.
The specific surface (m2/g) of silica fume typically ranges from 20 to 50 m2/g. This can be measured with the BET method or the nitrogen adsorption method.
When you inhale crystalline silica dust, it can cause silicosis, which is an occupational lung disease. And over time, constant exposure to silica particles causes permanent lung scarring, called pulmonary fibrosis.
Severe cases of silicosis can be disabling and even fatal. The inhaled silica dust enters the lungs and causes the formation of scar tissue. This affects your ability to breathe.
Silica fume reacts readily with the calcium hydroxide, which is produced during Portland cement hydration. Adding Silica fumes to concrete refines the pore structure. This then produces concrete with improved mechanical strength.
Silica fume is simply another term for microsilica and can be used interchangeably. They both mean the same thing. Other names for silica fume include volatilized silica, condensed silica fume, and silica dust.
Silica fume is not the same thing as concrete. Concrete is a construction material that's composed of cement, fine aggregates (sand), and coarse aggregates. When mixed with water, it hardens over time.
On the other hand, silica fume is a product used in cementitious applications such as concrete, shotcrete, repair products, and oil well grouts. It acts as both a filler and a pozzolan.
Silica fume for use in concrete comes in both wet and dry forms. Manufacturers tend to add it while producing the concrete at a plant.
Dark grey, grey, light grey, and pure white.
Densified Silica Fume, is a further processing of the original micro-silica fume to obtain a denser encrypted micro-silica fume.
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