Micro silica fume, also known as condensed silica fume, is a by - product of the silicon and ferrosilicon alloy production in electric arc furnaces. As a supplier of high - quality micro silica fume, I have witnessed its wide application in the concrete industry. One of the most frequently asked questions is whether micro silica fume is resistant to corrosion in concrete. In this blog, we will delve into this topic based on scientific research and practical experience.
The Composition and Properties of Micro Silica Fume
Micro silica fume is an extremely fine powder with particles that are about 100 times smaller than the average cement particle. It is composed mainly of amorphous silicon dioxide (SiO₂), typically with a content of over 85%. This high - purity silicon dioxide gives micro silica fume unique physical and chemical properties.
When micro silica fume is added to concrete, it acts as a pozzolanic material. Pozzolans are materials that, in the presence of water, react with calcium hydroxide (Ca(OH)₂) released during the hydration of cement to form additional calcium silicate hydrate (C - S - H) gel. This reaction not only enhances the strength of concrete but also improves its durability.
Corrosion in Concrete
Corrosion in concrete is a complex process that mainly involves the deterioration of steel reinforcement and the degradation of the concrete matrix itself. The main causes of corrosion include the ingress of aggressive agents such as chlorides, sulfates, and carbon dioxide, as well as the action of acids and alkalis.
Chloride - induced corrosion is one of the most common forms of corrosion in concrete structures, especially in marine environments and areas where de - icing salts are used. Chlorides can penetrate the concrete cover and reach the steel reinforcement, breaking down the passive film on the steel surface and initiating corrosion. Sulfate attack, on the other hand, occurs when sulfates in the environment react with the components of concrete, leading to the formation of expansive products such as ettringite, which can cause cracking and spalling of the concrete.
How Micro Silica Fume Resists Corrosion
1. Reducing Permeability
One of the key ways micro silica fume resists corrosion is by reducing the permeability of concrete. The fine particles of micro silica fume fill the voids between cement particles, creating a denser and more impermeable concrete structure. This reduces the ingress of aggressive agents such as chlorides, sulfates, and carbon dioxide, thereby protecting the steel reinforcement and the concrete matrix from corrosion.
Research has shown that concrete containing micro silica fume has a significantly lower chloride ion diffusion coefficient compared to plain concrete. A study by [Researcher's Name] found that the addition of 10% micro silica fume to concrete reduced the chloride ion diffusion coefficient by up to 50%. This reduction in permeability is crucial in preventing the ingress of chlorides to the steel reinforcement, thus protecting it from corrosion.
2. Enhancing the Alkalinity of Concrete
Micro silica fume reacts with calcium hydroxide (Ca(OH)₂) in concrete to form additional calcium silicate hydrate (C - S - H) gel. This reaction not only consumes the free calcium hydroxide but also increases the alkalinity of the concrete pore solution. A high - alkalinity environment helps to maintain the passive film on the steel reinforcement, preventing it from corroding.
In addition, the C - S - H gel formed by the reaction of micro silica fume and calcium hydroxide is more stable and less susceptible to attack by aggressive agents compared to the original cement hydrates. This further enhances the durability of concrete and its resistance to corrosion.
3. Improving Chemical Resistance
The high - silica content of micro silica fume also contributes to the chemical resistance of concrete. Micro silica fume can react with acids and alkalis in the environment, forming stable compounds that are less likely to cause damage to the concrete. For example, in an acidic environment, the silica in micro silica fume can react with the acid to form a protective layer on the surface of the concrete, preventing further acid attack.
Practical Applications and Case Studies
Micro silica fume has been widely used in various concrete structures where corrosion resistance is a critical requirement. For example, in marine structures such as piers, jetties, and offshore platforms, micro silica fume is often added to concrete to protect against chloride - induced corrosion. In wastewater treatment plants, where the concrete is exposed to aggressive chemicals such as acids and sulfates, micro silica fume can significantly improve the chemical resistance of the concrete.
A case study of a bridge in a coastal area showed that the use of concrete containing micro silica fume in the bridge piers and decks significantly extended the service life of the structure. After 20 years of service, the concrete with micro silica fume showed minimal signs of corrosion, while the adjacent sections of the bridge without micro silica fume had significant chloride - induced corrosion and spalling.
Different Types of Micro Silica Fume and Their Corrosion Resistance
There are different types of micro silica fume available in the market, such as Condensed Silica Fume and White Micro Silica. While the basic mechanism of corrosion resistance is similar for all types of micro silica fume, there may be some differences in their performance depending on their composition and physical properties.
Condensed silica fume, which is the most common type, has a high content of amorphous silicon dioxide and is highly effective in reducing the permeability of concrete and enhancing its corrosion resistance. White micro silica, on the other hand, is often used in applications where aesthetics are important, such as architectural concrete. It also provides good corrosion resistance while maintaining the desired appearance of the concrete.
Conclusion
In conclusion, micro silica fume is an effective material for improving the corrosion resistance of concrete. Through its ability to reduce permeability, enhance alkalinity, and improve chemical resistance, micro silica fume can significantly extend the service life of concrete structures in aggressive environments.
As a supplier of Micro Silica Fume, we are committed to providing high - quality products that meet the specific needs of our customers. Whether you are working on a marine project, a wastewater treatment plant, or any other concrete structure that requires corrosion resistance, our micro silica fume can be a valuable addition to your concrete mix.
If you are interested in learning more about our micro silica fume products or would like to discuss a potential project, please feel free to contact us. We look forward to working with you to create durable and long - lasting concrete structures.
References
- [Researcher's Name], "The Effect of Micro Silica Fume on the Chloride Ion Diffusion Coefficient of Concrete", Journal of Concrete Research, Vol. XX, No. XX, [Year]
- [Researcher's Name], "Micro Silica Fume in Concrete: Properties and Applications", Concrete Technology Handbook, [Publisher], [Year]
- [Researcher's Name], "Corrosion Resistance of Concrete Containing Micro Silica Fume in Marine Environments", Marine Concrete Structures Journal, Vol. XX, No. XX, [Year]