How silica fume enhances the properties of concrete?

The addition of silica fume to concrete improves the latter’s durability by reducing permeability and refining pore structure, leading to a reduction in the diffusion of harmful ions and the calcium hydroxide content, resulting in greater resistance to sulfate attack.

How does silica fume effect concrete?

Because of the high surface area of silica fume particles affecting the mobility of water within concrete, segregation and bleeding of concrete are virtually eliminated.

Is silica fume finer than cement?

Because of its chemical & physical properties, like high silica content & extreme fineness, silica fume is a very effective pozzolanic material. Concrete containing silica fume can have very high strength and can be very durable. Micro Silica Fume or Microsilica is finer particle than Cement.

What are the properties of silica fume?

Properties of Fresh Silica Fume Concrete

  • Silica fume concrete requires higher water content, for the same workability as of conventional concrete.
  • Low workability.
  • Low slump value.
  • Possibility of bleeding and segregation is low.
  • The mixture is cohesive.
  • High plastic shrinkage.

What is silica fume and its properties?

Silica fume is a by product resulting from the reduction of high – purity quartz with coal or coke and wood chips in an electric arc furnace during the production of silicon metal or silicon alloys. Silica fume is known to improve the mechanical characteristics of concrete.

Why does silica fume increase strength?

Silica fine is 100 times finer than the cement particles. Hence, the use of silica fume results a denser concrete matrix which impacts the strength parameters positively. Due to high pozzolanacity, reactivity and fine particles of Silica fume, It improves all hardened properties of concrete.

What are the desirable properties of silica fume?

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.

What is the common percentage of silica fume in concrete?

Silica fume has been used as an addition to concrete up to 15% by weight of cement, although the normal proportion is 7 to 10%. With an addition of 15%, the potential exists for very strong, brittle concrete.

What is the specific gravity of silica fume?

2.20–2.30
The specific gravity of silica fume is 2.20–2.30 (Khan & Siddique, 2011; Tafraoui et al. 2016; Thomas, 2013). The surface area of silica fume particles can range between 13,000 and 30,000 m2/kg, measured by nitrogen absorption equipment (Valipour et al.

Is silica fume used in concrete?

9 – Use of silica fume in concrete It reacts readily with the calcium hydroxide, which is produced during Portland cement hydration. Silica addition refines pore structure and produces concrete of improved mechanical strength.

What is the density of silica fume?

The bulk density of the as-produced silica fume ranges from 130 to 430 kg/m3.