One of the most important materials added to concrete is microsilica. Microsilica, also known as colloidal silica, is a very fine material that is extracted in a specific way that we will discuss during the article. It is characterized by its ability to improve the properties of concrete. We will also learn what happens when microsilica is added to concrete in the following.
What is microsilica?
Microsilica is a very fine material, made up of very small particles of silicon dioxide (SiO2), and is formed as a by-product during the silicon and steel manufacturing process.
Microsilica is extracted during the process of heating sand in special furnaces to produce metallic silicon, or it is also extracted during the steel smelting process. After that, it is converted into a very fine powder with particle sizes ranging between 1 and 100 microns, making it a very fine material in various industries.
This material has unique properties that make it a material with multiple applications in different industries, and thanks to its small particles, it has a wide surface area that can interact effectively with other materials.
Microsilica is used in many industrial applications, and one of its most famous applications is adding microsilica to concrete, where it enhances the properties of the concrete. It is also used in the manufacture of coatings, insulating materials, and electronic industries.
Thanks to these properties and features, microsilica is a versatile material that plays an important role in improving performance in many fields.
Is there a difference between silica fume and microsilica?
Depending on the context and the required use, there will be a difference between them, but basically they are the same material.
Silica fume is the common name for the material that forms as a by-product during the production of silicon alloys or metallic silicon in electric furnaces. This fume consists of very fine particles with a diameter of less than 1 micron, making it an effective material for improving the properties of concrete, as it helps to increase strength and durability and reduce permeability.
Microsilica is a term sometimes used to refer to the same material, but it may be more associated with products that have undergone certain treatment or purification to meet specific standards in the building and construction industry. Thanks to its unique composition, silica fume is widely used in improving high-performance concrete, where it helps reduce porosity and increase resistance to environmental factors such as corrosion and cracking.
Therefore, whether it is called “silica fume” or “microsilica,” the benefits and uses remain the same, with the possibility of differences in the degree of purity or processing that the material has undergone.
What happens when microsilica is added to concrete?
When microsilica is added to concrete, substantial improvements are made to its properties, making it more efficient in projects requiring high strength and long-term durability. This is due to the chemical reaction of microsilica with cement, in addition to its role in improving the structure of concrete and reducing porosity.
First: Increasing the strength of concrete
Microsilica greatly improves the mechanical strength of concrete, as the micro-silica particles fill the spaces between the cement particles, increasing the density of the concrete and reducing porosity.
It also reacts with the calcium hydroxide produced during the cement hydration process, leading to the formation of hydrated calcium silicate (C-S-H), compounds that give concrete its high strength and durability. As a result, concrete becomes more resistant to heavy loads and more resistant to compression and cracking.
Second: Improving permeability resistance
One of the main benefits of adding microsilica is reducing the permeability of concrete, as it reduces the size of internal pores, thus reducing the absorption of water and harmful chemicals.
This makes concrete less susceptible to damage from constant exposure to moisture and environmental pollutants, and it also protects concrete structures from water leakage, which is crucial in bridges, dams, and underground facilities.
Third: Increased resistance to corrosion and chemical reactions
Microsilica makes concrete more resistant to environmental and chemical factors, protecting it from deterioration caused by exposure to chlorides, sulfates and other harmful chemicals.
This makes microsilica-enriched concrete suitable for harsh environments such as marine and industrial facilities exposed to high corrosive conditions. Reducing permeability also prevents chemicals from reaching the reinforcing steel, thus reducing the risk of corrosion and increasing the lifespan of concrete structures.
Fourth: Improving the resistance of concrete to high temperatures
Among the distinctive properties of microsilica is its ability to improve the resistance of concrete to high temperatures, as it reduces thermal cracking resulting from expansion and contraction.
This makes it ideal for use in facilities exposed to high temperatures, such as furnaces and industrial facilities. The low porosity also enhances the stability of the concrete in different thermal conditions, which maintains its cohesion for long periods.
In general, microsilica is an effective additive that enhances and strengthens the performance of concrete in various environments and applications, making it stronger, more durable, and more resistant to various environmental factors.
Comparing microsilica with other concrete mix components
When designing concrete mixes, a variety of materials are used to improve the properties of concrete in terms of strength, durability, and resistance to environmental factors, but the effects of each material on concrete vary according to its chemical composition and how it reacts with cement.
The following table shows a comparison between microsilica and other components used in concrete mixes, highlighting the effect of each on the different properties of concrete:
| component | Source and Use | molecular size | Impact on concrete strength | Effect on permeability | Corrosion resistance | heat resistance | Impact on operational | Cost |
| Microsilica | A byproduct of silicon manufacturing, used to improve strength and durability. | Less than 1 micron | Strength is greatly increased due to the formation of hydrated calcium silicate. | It significantly reduces permeability. | Improved resistance to corrosion and chemical reactions | It increases the concrete’s resistance to high temperatures. | It reduces operational efficiency and may require additives to improve castability. | Relatively high |
| Portland cement | The basic material in concrete reacts with water to form a binding paste. | 10-50 microns | Determines the basic strength of concrete | It depends on the water-to-cement ratio. | Moderately corrosion resistant | It can withstand heat up to a certain limit, but may lose its strength at high temperatures. | It depends on the ratio of water and additives. | Medium |
| Fly ash | A byproduct of coal combustion, used to improve operational efficiency and fuel economy in the mix. | 1-100 microns | It improves strength in the long term, but at a slower rate. | It reduces permeability but is less effective than microsilica | It improves corrosion resistance but is weaker than microsilica | It helps improve heat resistance | It improves operational efficiency and reduces the need for water. | Less than microsilica, economical |
| furnace slag (GGBS – Ground Granulated Blast Furnace Slag) | A byproduct of iron manufacturing, used to improve durability and reduce heat generated by the reaction. | 1-100 microns | It improves strength slowly, but gives good results in the long run. | It reduces permeability and improves concrete durability. | It improves corrosion resistance well | It increases heat resistance but is less effective than microsilica | It improves operational efficiency and reduces hydration heat. | Moderate to high |
| Limestone (Limestone Powder) | A filler material used to increase the density of concrete and improve workability. | 1-50 microns | It does not significantly affect strength but it helps improve cohesion. | Slight effect on permeability | It does not significantly improve corrosion resistance. | It has no significant effect on heat resistance. | It improves workability and makes concrete easier to pour. | low |
Microsilica is most effective at improving concrete strength, abrasion resistance, and reducing permeability, but it may negatively affect workability and requires additives to improve its performance.
Fly ash or coal ash and furnace slag offer good improvements in strength and durability, but their effect is slower than microsilica.
As for limestone, it is used only as a filler material and does not have a major effect on the strength or durability of the concrete, but it does help to improve workability.
Portland cement is the basic component of concrete, but adding microsilica or other materials can enhance its properties as needed.
In short, microsilica is the best choice when the goal is to achieve the highest possible strength and durability, especially in harsh environments such as marine structures, bridges, and industrial facilities. However, it requires modifications to the mix to improve operational efficiency and reduce costs. But in general, adding microsilica to concrete is one of the most effective materials that can be added to concrete.
The best company to supply you with microsilica
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