Silica Fume for Concrete

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Undensified Silica Fume

Densified Silica Fume

Silica Fume for Concrete

Being an effective pozzolanic material, silica fume is commonly added to concrete to improve its properties, in particular bond strength, compressive strength, and corrosion resistance.

Silica fume presents a neutral inorganic filler with incredibly stable chemical and physical properties. It does not participate in the curing reaction, does not contain crystalline water, and does not affect the reaction metabolism.
Adding silica fume to concrete can increase thermal conductivity and flame retardant, as well as change adhesive viscosity.
It has great adsorption performance, produces no agglomeration phenomenon, is easy to mix, and offers good infiltration for various types of resin.
The addition of silica fume allows reducing epoxy resin’s exothermic peak temperature of curing reaction, the shrinkage rate of solidified products, and their linear expansion coefficient. This allows preventing cracking by eliminating internal stress.

Applications of Silica Fume in Concrete

High-performance concrete (HPC) produced with silica fume has been identified as one of the most valuable advanced materials required for the construction of infrastructure.

In addition to enhanced durability and increased strength, HPC containing silica fume provides increased resistance to abrasion, chemicals, and corrosion, enhanced toughness, and improved sustainability and life-cycle cost efficiencies.

Parking decks, highway bridges, bridge deck overlays, and marine structures are subject to continuous deterioration due to abrasion, rebar corrosion current, and chemical attack. Silica fume is used to protect concrete against seawater, deicing salts, heavy impact, and traffic, thus minimizing maintenance expenses.

Key advantages of high-performance concrete include:

Increased impact and abrasion resistance on floors, decks, overlays, and vertical structures
Extremely high electrical resistivity
The very low permeability of water intrusion and chloride
Superior resistance to chemical impact from acids, chlorides, sulfates, and nitrates

High-strength concrete produced with silica fume provides greater design flexibility for engineers and architects. It is traditionally used in high-rise buildings for the benefit of increasing usable space, as it allows for the use of smaller columns. High-strength concrete containing silica fume is often used in prestressed and precast girders, allowing larger spans in structural bridge designs.

Key benefits of high-strength concrete include:

High elastic modulus exceeding 7 million psi (40,000 Mpa).
Compressive strength of up to 20,000 psi (140 Mpa).
High early strength for precast applications and fast-track projects.
High flexural strength of up to 2,000 psi (12 MPa).

Silica Fume Concrete Properties

Pozzolanic Reaction

Silica Fume Concrete reacts with lime during cement hydration to form additional calcium silicate hydrates (C-S-H gel) which bonds the components together creating a dense matrix.

Strength

Silica Fume Concrete improves component packing and adhesion, which has a direct impact on the mechanical properties, especially on strength.

Alkali Reaction

Silica Fume Concrete protects the concrete against the alkali reaction. Its fine and amorphous particles react with cement alkalies and reduce their content in the concrete before hardening.

Porosity/ Permeability/ Resistance to Corrosion

Addition of Silica Fume Concrete reduces porosity by decreasing pore size. Porosity and permeability reductions inhibit the penetration of aggressive agents. The use of Silica Fume Concrete is beneficial to prevent concrete from corrosion in difficult environments: harbors, airports, chemical areas, and coastal buildings are common examples.

Filler Effect

Silica Fume Concrete is 100 to 150 times smaller than a cement particle and can fill the interstitial voids. The packing effect reduces strongly the concretes porosity and permeability.