Silica fume is often used as a building material.
It is gaining more and more popularity due to its delicacy and benefits. Due to its thinness, it offers even more advantages to the construction industry.
It is a light-dark gray cementitious material composed of at least 85% ultrafine, amorphous, non-crystalline spherical silica particles.
It is a byproduct of the production of silicon metal or ferrosilicon alloys.
Due to its chemical and physical properties, it is a very reactive pozzolan. Concrete with silica fume can have very high strength and good durability.
Furthermore, it is a very thin material, about 1/50th the size of regular Portland cement. The average particle size varies between 0.1 and 0.3 microns and the minimum specific surface area is about 15,000 m2/kg.
The extreme fineness, large surface area and high amorphous silicon dioxide content give silica smoke superior pozzolanic properties.
The main benefits of silica fume include reducing bleeding and segregation in fresh concrete and improving the strength and durability of hardened concrete.
The low porosity with its fineness reduces permeability. Furthermore, the following advantages and disadvantages can be identified.
Benefits of silica fume
- segregation and bleeding; significantly reduces bleeding.
- It can be used with fly ash or blast furnace slag to develop strength at a young age.
- Increasing chloride permeability
- Increase plastic shrinkage
- Improves adhesion to steel
- Significant reduction in alkali-silica reactivity
- Offers excellent resistance to sulfate and seawater attack
- Reduce steel corrosion
Disadvantages of silica fume
- Processability: Due to the fineness of the material, a more cohesive mixture is created. Therefore, there is a greater demand for water. However, this can be reduced by adding a suitable flow agent.
- set time; Adding a small amount (250 – 300 kg/m 3 ) has no significant influence on setting time. However, an increase in salary may lead to a delay in termination.
- Longer mixing time required
