In recent times, concrete has seen remarkable evolution, making it a versatile and reliable construction material in the construction industry. While making any building or multistorey building, concrete is one of the most vital components. The crucial material in concrete is cement, which binds all the ingredients together. Generally, cement includes different adhesive materials, with the binder being its key characteristic. Portland cement is the primary type used in concrete, serving as a binder that holds all the ingredients together. In concrete, cement not only binds the core components into a cohesive unit with the aid of water but also fills the microvoids, enhancing its overall structure.
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The high use of cement in the construction industry results in increasing the level of CO2 in the atmosphere. Thus, the alternative to cement is explored through research, and found that silica fume is a suitable admixture in concrete. Silica fume also called micro silica is a highly pozzolanic component and it is widely recognized for enhancing the properties of concrete. By using silica fume, it is possible to get extremely strong and long-lasting concrete. Through various studies, it is evident that mixing silica fume in concrete can improve its mechanical properties. In this blog, we’ll dive into the insights about silica fume and its potential as a cement replacement.
Effects of Silica Fumes in Concrete
In the construction industry, silica fume is generally used in two ways: either mixed directly into cement or added to the concrete. In fact, both methods work through the same mechanism and provide a similar enhancement result. In this section we will know more about silica fume effects in concrete as follows:
The silica fumes effect in concrete is divided into two types i.e., chemical effect and physical effect.
1. Chemical Effect:
Silica fume is an extremely reactive pozzolanic material with aluminous and siliceous properties. It has few to zero cementitious qualities on its own. Nevertheless, when moisture comes in touch with silica fumes, it actively reacts with calcium hydroxide at room temperatures resulting in forming compounds with cementious properties.
2. Physical Effect:
The presence of various smaller particles enhances the properties of concrete. This phenomenon is often called particle packing or micro-filling. Several tests showed that the carbon black and plain cement mixtures had comparable strengths at 7 and 28 days, despite the carbon black mixture containing 10% less cement by weight.
Having a glance at the effects of silica fume on concrete, let’s have a look at its advantages due to which silica fume is popular in the construction industry.
Advantages of Silica Fumes in Concrete
Silica fume is popular due to its mechanical properties that’s why it is widely used in the concrete mixture. In this section, we will explore those unheard advantages.
- High Strength of Concrete: By mixing silica fumes in concrete, the concrete strength increases by enhancing the interlocking between the aggregate which makes the concrete. Thus, silica fume is utilized to achieve compressive strengths of up to 20,000 psi in on-site conditions.
- Improved Workability of Concrete: By adding silica fume to concrete, the workability performance of concrete can be enhanced. It is achieved due to the reduction of segregation and bleeding of concrete. The inclusion of silica fume in concrete can expand the contact point between solid and solid leading to enhancement of the cohesion inside the concrete.
- Increased Wear Resistance: The addition of silica fume helps to improve the abrasion resistance on floors, roofs, deck slabs, drapes, and more. Concrete’s wear resistance mostly depends on its strength. Stronger concrete, made with high density and hard aggregates, lasts longer and resists wear better.
- Resistance Against Chemicals: Incorporation of silica fume into concrete, improves the acid resistance or sulfate resistance i.e., resistance against acids, nitrites, chlorides, and sulfides. Also, the calcium hydroxide content in concrete can be reduced by adding silica fume to concrete.
- Lowers Permeability: The durability of concrete against erosive water largely depends on its impermeability. Silica fume has a reducing effect on permeability so that water and chloride ions should not penetrate.
- Enhances Durability of Concrete: Enhancing the durability of concrete means improving its ability to withstand various stresses and environmental factors over time, leading to longer-lasting structures. The greatest advantage of using silica fume is its capacity to improve the concrete’s flexural strength and durability.
- Electrical Resistance: Silica fume has a more beneficial effect, when it is added to the concrete mixture it increases the electrical resistivity of the structures by 20 to 100 times more compared to the conventional concrete.
Micro Silica Fume Percentage in Concrete
When deciding to add or mix silica fume in concrete, it is essential to know the percentage and its effects on the cement. Let’s have a glance at it.
The percentage of silica fume affects the performance of concrete. Like more the content of SiO2, the higher the performance of micro silica. In general, the silica fume should have a content of over 85% and then the carbon present in the silica fume will absorb some of the air-entering agents in the concrete, so the loss on ignition must be kept under 7% to manage carbon and water levels. In addition to that, the fineness of the micro silica should be kept below 45 um, with particles larger than 45 microns making up less than 10% of the material.
Technically, the quantity of micro silica added to the concrete mixture should be between 5% to 10%, not much higher or lower. This range is treated as the good level. For instance, in the case of commercial concrete, the resistance to the cold can be reduced after a dosage of more than 15%.
You can measure the water absorption and compressive strength of the concrete by varying the percentage of silica fume to the cement, like adding 2%, 4%, 6%, 8%, and 10% silica fume into the concrete to see the outcome.
The more you increase the silica fume content, the more water absorption rate of foam concrete you can observe, and as a result, the 7-day compressive strength varies. The compressive strength can increase to 2.3MPa when the silica fume content is around 6% in the concrete, i.e., higher than the ordinary sample without silica fume. Post 28 days, the compressive strength reaches 2.7 MPa, and the water absorption rate drops by 2%. Overall, the improvement is quite significant.
Is Silica Fume a Suitable Replacement for Cement?
When cement is replaced by silica fume for construction, it tends to work like fly ash, which offers the following advantages: improving workability of the concrete mix, reduction in heat generated during hydration, significant improvement in corrosion resistance and impermeability, frost resistance, and help in controlling the alkali-aggregate reaction. Therefore, its effectiveness is much higher than fly ash. This early reaction of the SiO2 in silica fume with Ca(OH)2 to hydrated calcium silicate increases the early strength of concrete.
Silica fume is commonly used to replace between 5% and 15% of the cement in a concrete mix. If it is more than 20%, the slurry of cement will be too viscous. Besides, there will also be an increase in the water demand for mixing, so a water reducer is necessary to acquire its best results. Silica fume enables concrete to pump well and resist further vibration without segregation, and its fluidity is improved. When using the same pouring method, concrete containing silica fume can achieve a slump that’s 500px higher than ordinary concrete. However, concretes with silica fumes are more sensitive to early shrinkage cracks and, therefore, require very careful control over curing conditions.
In this day and age, silica fume is widely used, particularly to achieve high-strength and ultra-high-strength concrete, concrete with high impermeability, and underwater anti-dispersion concrete, among other specialized applications.
You must be wondering then where to get the top-quality silica fume for a construction project. Don’t worry, keep reading to learn the brand that is offering the best silica fume to use in construction projects.
Presenting Addage Micro Silica Powder (Fumecrete 90)
Fumecrete 90 is one of the top-quality silica powders manufactured by Sakshi Chem Sciences Pvt Ltd. It is an extremely reactive pozzolan powder that is used relatively in small amounts to enhance concrete properties. Adding Addage Fumecrete 90 to the concrete enhances flexural, bonding, and compressive strength.
Micro Silica Powder is a mineral admixture produced from a very fine glassy sphere of Silicon Dioxide (SiO2). It can also be used to prevent concrete cancer as it has resistance to ASR (Alkali-Silica Reaction). This silica powder can be used to avert corrosion of steel reinforcement.
To sum up, silica fumes should be used with concrete to enhance its workability and mechanical properties. However, it should be added or mixed in a specific percentage to achieve certain results as mentioned above in the blog.
To get the best quality silica fume (silica powder) for construction projects, then get in touch with the Sakshi Chem Sciences Pvt Ltd representatives. Our team is trained to offer you the best quotations and product range to meet your requirements. We have more than 200+ construction chemicals that are widely recognized in the construction industry for their top-notch quality and cost efficiency. Connect with us today to get complete support on construction chemicals.