silica fume raw concrete
silica fume for raw concrete

Silica Fume for Raw Concrete

Concrete containing cement, in a fluid state called “slurry”, produces hydration that absorbs water and hardens to maintain its strength, and finally forms the “structure” of the building. The places and construction methods for this series of functions can be roughly divided into three types:

Cast-in-place concrete: performed on the final parts of the building (columns, walls, floors, etc.)

PC (Precast Concrete): The above-mentioned hardening process is carried out in factories and other places, and the main body of the building is fixed with metal parts at the construction site.
in between.

Mix some of 1 and 2 together and use the strengths of both.

Silica fume can improve the performance of concrete mixture, reduce air bubbles on the surface of concrete, improve the strength of concrete surface, make the surface of concrete smooth, inhibit the carbonation of concrete, resist the erosion of harmful external media, and help improve the durability of concrete.

When mixing fair-faced concrete, high-efficiency water reducers with low air-entraining components and moderate retardation should be selected, with a water reducing rate of >20% and an air content of <1.7%.

Silica fume concrete, also known as microsilica concrete, has become increasingly popular in the construction industry due to its many unique properties and advantages. This material is formed from a by-product of silicon and ferrosilicon alloy production, making it both environmentally friendly and cost-effective.

Advantages & Disadvantages of Silica Fume in Concrete

♦ Advantages

• Silica fume enhances the properties of fresh and hardened concrete.
• Silica fume reduces segregation and bleeding.
• High durability
• The finishing process is efficient due to low bleeding.
• High early compressive strength
• High flexural strength and modulus of elasticity
• High bond strength
• Suitable for mass concreting since it prevents thermally induced cracking.

♦ Disadvantages:

• The expense of silica rage is high.
• Require more water to keep a steady downturn.
• Unfortunate toughness against freeze-defrost assault.
• Accessibility issues.
• SF is excessively gooey and challenging to apply.

How Does Silica Fume Work in Concrete?

When added to concrete, silica fume initially remains inert. Then, once the water starts reacting with portland cement in the mixture (hydrating), the primary chemical reaction produces two important chemical compounds:

  • Calcium Silicate Hydrate (CSH), the crystalline compound responsible for the material’s strength
  • Calcium Hydroxide (CH), a by-product that acts as a filler and lines pores within the concrete

Next, a pozzolanic reaction occurs between Calcium Hydroxide and silica fume, producing additional Calcium Silicate Hydrate compounds that fill up the voids around the hydrated particles of cement. These additional CSH compounds provide concrete with a denser matrix in areas that would have otherwise remained as small voids subject to potential ingress. As such, concrete develops improved flexural, compressive, and bond-strength properties.

Effect of Silica Fume on the Properties of Concrete

TThe use of silica fume gives rise to a variety of concretes with different properties which can be used in fresh as well as in the hardened state with less cement. Silica fume provides high durability to the concrete. Where at one end there are advantages associated with it, there are few difficulties in the form of disadvantages too associated to work with silica fume. Therefore, usage of water-reducing admixtures or high range water reducing admixtures or both is recommended to maintain the desired w/c ratio as well as workability as the addition of silica fume increases water demand.If this is handled properly, it is certainly a new-age material that can achieve high strength concrete above M40 grade and simultaneously give impermeable, dense and durable concrete, thereby extending the basic life of the structure and lessening the pollution.

In conclusion, silica fume concrete is a highly versatile material that offers numerous advantages over traditional concrete. It has superior strength, durability, and chemical resistance, making it suitable for a wide range of construction projects. Its use also results in a significant reduction of environmental impact, making it a sustainable choice. From high-rise buildings to transportation infrastructure, silica fume concrete has proven to be a reliable and cost-effective option for various applications. As technology continues to advance, we can expect to see even more innovative uses for this remarkable material. With its unique properties and multiple benefits, silica fume concrete is undoubtedly a game-changer in the world of construction.

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FAQs on Silica Fume Concrete

What is silica fume concrete?

Concrete is made from cement, silica fume, fine and coarse aggregate, and water.

What are the desirable properties of silica fume concrete?

Compressive strength, flexural strength, and bond strength of silica fume are better than normal strength concrete. In addition, the durability of this type of concrete fends off the most aggressive chemical attacks.

What are the properties of fresh silica fume concrete?

Low workability, considerably cohesive, low bleeding and segregation, and low slump value.

What are the advantages of silica fume concrete?

High durability, segregation and bleeding, efficient finishing process, high early compressive strength., high flexural strength and modulus of elasticity, high bond strength., and suitable for mass concreting since it prevents thermally induced cracking.

What are the applications of silica fume concrete in civil engineering?

The applications of silica fume concrete in construction are high-rise buildings, parking structures, dam structures, nuclear waste storage facilities, and shotcrete rehabilitation.