Silica fume is a byproduct of producing silicon and ferrosilicon alloys, and it has been used as a supplementary cementitious material in concrete since the 1950s. It is a highly reactive pozzolan, which means it can react with calcium hydroxide in the presence of water to form a stable and durable cementitious product. Recently, granular silica fume has emerged as a new form of silica fume that offers several advantages over the conventional silica fume.
What is Granular Silica Fume?
Granular silica fume is a new form of silica fume that is produced by cooling and solidifying the gas stream that contains silica fume particles. It is called “granular” because it has a granular texture and is in the form of small, free-flowing spherical particles. Unlike the conventional silica fume, which is in the form of fine powder or dust, granular silica fume is easy to handle, transport, and store. It does not require special equipment or precautions, and it can be added to concrete mixtures directly.
Properties of Granular Silica Fume
Particle Size
The particle size of granular silica fume ranges from 1 to 10 micrometers, which is similar to the conventional silica fume. However, the particles of granular silica fume are more spherical and uniform in size, which enhances their reactivity and packing density.
Bulk Density
The bulk density of granular silica fume ranges from 250 to 700 kg/m3, which is lower than the conventional silica fume. This is because granular silica fume particles are more spherical and have lower packing density. However, this does not affect their reactivity or performance in concrete.
Chemical Composition
The chemical composition of granular silica fume is similar to the conventional silica fume, which is mostly composed of silicon dioxide (SiO2) with small amounts of other elements such as aluminum, iron, and calcium. The purity of granular silica fume can vary depending on the source material and production process.
Applications of Granular Silica Fume
Granular silica fume can be used as a supplementary cementitious material in concrete to enhance its strength, durability, and impermeability. It can also reduce the amount of cement needed, which can lower the cost and carbon footprint of concrete production. Granular silica fume can be added to concrete mixtures directly, and it can improve the workability and pumpability of the mixtures.
Granular silica fume can be used as a filler or binder in refractory materials such as castables, gunning mixes, and ramming mixes. It can enhance the strength, abrasion resistance, and thermal shock resistance of these materials.
Oil and Gas Industry
Granular silica fume can be used as a weighting agent in drilling fluids for oil and gas wells. It can increase the density and stability of the fluids and prevent blowouts and other drilling problems.
Other Applications
Granular silica fume can also be used in other applications such as ceramics, composites, and coatings. It can enhance the mechanical, thermal, and electrical properties of these materials.
Benefits of Granular Silica Fume
Improved Strength and Durability
Granular silica fume can enhance the strength and durability of concrete and other materials by reducing the porosity, increasing the packing density, and promoting pozzolanic reactions. It can also improve the resistance to freeze-thaw cycles, alkali-silica reactions, and chemical attacks.
Reduced Permeability
Granular silica fume can reduce the permeability of concrete and other materials by filling the pores and capillaries with fine particles and forming a denser and more compact structure. This can improve the resistance to water penetration, chloride ion penetration, and carbonation.
Improved Workability
Granular silica fume can improve the workability and pumpability of concrete mixtures by reducing the water demand and increasing the viscosity and thixotropy of the mixtures. This can enhance the placement, compaction, and finishing of the concrete.
Reduced Heat of Hydration
Granular silica fume can reduce the heat of hydration of concrete and other materials by reducing the amount of cement needed and promoting pozzolanic reactions. This can prevent thermal cracking, shrinkage, and other problems caused by excessive heat.
Reduced Carbon Footprint
Granular silica fume can reduce the carbon footprint of concrete and other materials by reducing the amount of cement needed, which is one of the most carbon-intensive materials in the world. It can also reduce the energy consumption and emissions associated with cement production.
Conclusion
Granular silica fume is a new form of silica fume that offers several advantages over the conventional silica fume. It has a granular texture, is easy to handle and transport, and can enhance the properties of concrete and other materials. It has several applications in various industries, such as concrete, refractory materials, oil and gas, ceramics, composites, and coatings. It can improve the strength, durability, impermeability, workability, and reduce the carbon footprint of these materials. Granular silica fume is a promising material that can contribute to the sustainability and resilience of our built environment.
FAQs
Is granular silica fume more expensive than conventional silica fume?
Granular silica fume can be more expensive than conventional silica fume due to its production process and properties. However, its benefits and ease of use can offset the cost difference in certain applications.
Is granular silica fume hazardous to health?
Granular silica fume is not hazardous to health if handled properly. It is recommended to wear a dust mask and gloves when handling it to avoid inhalation and skin contact.
Can granular silica fume be used in high-performance concrete?
Yes, granular silica fume can be used in high-performance concrete to enhance its strength, durability, and impermeability. It can also reduce the shrinkage and thermal cracking of the concrete.
How is granular silica fume produced?
Granular silica fume is produced by cooling and solidifying the gas stream that contains silica fume particles. The particles are then screened and classified to obtain a granular texture and uniform particle size distribution.
What is the shelf life of granular silica fume?
Granular silica fume has a shelf life of several months if stored in a dry and cool place. It should be protected from moisture and contaminants that can affect its reactivity and performance.
