Concrete is one of the most commonly used construction materials worldwide. Innovations and improvements in concrete technology have led to the use of additives that can enhance the properties and performance of concrete. One increasingly popular additive is fly ash.
What is Fly Ash?
Fly ash is a byproduct of burning coal. The fine ash that is carried out with exhaust gases is trapped and collected by pollution control devices like electrostatic precipitators or bag filters. This fine ash is what we call fly ash.
Fly ash consists of extremely fine particles, ranging in size from a few micrometers to over 100 micrometers. These particles are typically spherical in shape and contain various metal oxides such as silica (SiO₂), alumina (Al₂O₃), and calcium oxide (CaO), which give fly ash its unique properties.
Because its composition is similar to cement, fly ash is often used as an additive in concrete production. When mixed with Portland cement, fly ash reacts with calcium hydroxide (Ca(OH)₂) produced during the cement hydration process, forming compounds similar to cement (calcium silicate hydrate). This reaction helps improve the strength and durability of concrete.
To better understand the workings of this unique material, let's explore the benefits of concrete with fly ash.
Enhancing Concrete Strength
Fly ash increases the strength of concrete over time. Concrete mixed with fly ash tends to have higher long-term strength (28 days or more) compared to conventional concrete. Fly ash reacts with calcium hydroxide in concrete to form additional calcium silicate hydrate compounds, which strengthen the concrete's structure.
Reducing Permeability
One of the main issues with concrete is its permeability to water and aggressive chemicals, which can cause internal damage. Fly ash helps reduce the permeability of concrete by filling the tiny pores that form during mixing and curing. This makes the concrete more resistant to water absorption and harmful chemicals.
Improving Resistance to Sulfates
Concrete is often exposed to harsh environmental conditions, including sulfate-containing groundwater, which can damage it. Fly ash improves the sulfate resistance of concrete by reducing the amount of calcium hydroxide available to react with sulfates, thereby minimizing the risk of ettringite formation, which can cause expansion and damage.
Lowering Heat of Hydration
The hydration process of Portland cement generates heat, which can cause cracks in concrete, especially in large structures like dams or thick foundations. Fly ash has slower reactivity compared to Portland cement, resulting in a lower heat of hydration. This helps reduce the risk of thermal cracking and enhances the concrete’s durability.
Environmental Sustainability
Using fly ash in concrete is an eco-friendly approach. By utilizing industrial byproducts like fly ash, we reduce the amount of waste sent to landfills. Moreover, decreasing the use of Portland cement helps reduce carbon dioxide emissions, as cement production is one of the largest contributors to global CO2 emissions.
Improved Workability
Fly ash improves the workability of fresh concrete. Its fine and spherical particles act as lubricants in the concrete mix, enhancing fluidity and making it easier to pour and compact. This can also reduce the amount of mixing water needed, contributing to stronger concrete.
Better Volume Stability and Resistance to Freeze-Thaw Cycles
Concrete with fly ash exhibits better volume stability and is more resistant to freeze-thaw cycles. Fly ash helps minimize expansion and contraction caused by extreme temperature changes, reducing the risk of cracking and damage.
Cost Savings
In many cases, fly ash can reduce the cost of concrete production. Fly ash is generally less expensive than Portland cement, which can lower raw material costs. Additionally, the improved durability of concrete with fly ash means lower maintenance and repair costs in the long term.
With numerous benefits that are advantageous in terms of time, cost, and environmental impact, it’s no wonder that many construction products are now incorporating fly ash, including our company, Coretex Chemical Solutions. This is a testament to our commitment to the environment and the sustainability of our planet. It’s not too late to start caring for the earth. If not us, who else?
