Clitheroe
Shap
Horwich, Bolton
Chorley
Horwich, Bolton
Clitheroe
Shap
Horwich, Bolton
Chorley
Horwich, Bolton
Fly ash is a fine, powdery substance created as a by-product during the combustion of coal in power stations. Once considered waste, this material is now widely valued in the construction industry for its ability to enhance the properties of concrete.
As the sector moves towards more sustainable practices, fly ash has become an increasingly popular choice thanks to its strength-enhancing and eco-friendly credentials.
At Armstrongs, we supply high-quality aggregates, such as pink shap, sandstone, and granite, that form the foundation of high-performance concrete.
Our sister company, AMIX, uses these materials to produce bespoke concrete mixes, many of which incorporate fly ash to meet specific strength, durability, and sustainability goals.
Together, we support forward-thinking construction projects across the North West and beyond.
Fly ash is generated during the burning of pulverised coal in thermal power plants. As the coal combusts, fine particles rise with the flue gases and are captured using electrostatic precipitators or filter bags, this captured residue is what we know as fly ash.
With its fine, powdery consistency and pozzolanic properties, fly ash reacts chemically with calcium hydroxide in the presence of water to form compounds that contribute to concrete strength and durability.
These characteristics make it an excellent addition to cementitious materials in construction.
Fly ash used in concrete is generally classified into two main types: Class F and Class C. Class F fly ash is typically derived from bituminous coal and has low calcium content. It offers excellent long-term strength and is particularly good at enhancing durability and resistance to chemical attack.
Class C fly ash, on the other hand, comes from lignite or sub-bituminous coal and contains higher levels of calcium, which allows it to exhibit both cementitious and pozzolanic properties.
In the UK, Class F fly ash is more commonly used due to its compatibility with the types of concrete most often produced in British construction.
Incorporating fly ash in concrete offers a number of advantages. It improves workability by making the mix smoother and easier to place. It also reduces the overall water demand, helping to produce denser concrete that resists cracking and shrinkage.
Over time, fly ash contributes to increased compressive strength, meaning structures become stronger the longer they cure.
From an environmental standpoint, using fly ash concrete helps divert industrial by-products from landfill and reduces the reliance on Portland cement, one of the most carbon-intensive
Fly ash can be used in two key ways in concrete production: as an additive or as a partial replacement for traditional Portland cement. When used as an additive, it enhances performance without significantly changing the mix design. As a replacement, it can substitute up to 30% or more of the cement content, depending on the application and required strength.
This substitution not only lowers the carbon footprint of the mix but also extends working time, which can be particularly helpful in large pours or hot weather. The end result is a more sustainable, durable, and cost-effective concrete solution.
At AMIX, our ready mix concrete is designed around each project’s unique requirements. By incorporating fly ash into bespoke concrete formulations, we’re able to offer mixes that are easier to pump, more durable, and longer-lasting.
Whether it’s a commercial foundation or an infrastructure project with tight performance specs, fly ash plays a key role in delivering reliable results.
Our aggregates at Armstrongs, sourced from five active quarries across the North West, help ensure consistent quality and performance in every AMIX mix. To find out more about how AMIX uses fly ash in concrete, visit our AMIX page here.
Fly ash has a noticeable impact on how concrete performs over time. While it may slow the initial strength gain in the early curing stages, particularly within the first 7 days, it delivers significant benefits in the long term.
Fly ash concrete tends to achieve higher ultimate strength, greater durability, and improved resistance to environmental stressors compared to mixes made with cement alone.
Because of its pozzolanic properties, fly ash in cement helps reduce permeability, which makes the hardened concrete more resistant to water ingress and chemical attack.
It also enhances protection against sulphate attack and alkali-silica reaction, both of which are common causes of premature concrete deterioration. In short, while early patience is needed, the payoff is stronger, longer-lasting structures.
In addition to long-term strength benefits, fly ash in concrete also improves workability. Its fine particle size fills voids between aggregate grains, resulting in a smoother, more cohesive mix.
This is especially useful in mixes with a lower water-to-cement ratio, where maintaining flow and ease of placement can be challenging.
From a practical standpoint, this improved flowability makes concrete easier to pump, spread, and finish, reducing labour and improving the final surface appearance. These characteristics make fly ash concrete particularly attractive in architectural and infrastructure projects where both durability and a clean finish are essential.
No matter how advanced the cement mix is, the performance of fly ash concrete still depends heavily on the quality of the aggregates used. Strong, stable mixes require aggregates that are clean, well-graded, and consistent in size and shape.
At Armstrongs, we supply premium-grade aggregates from our five active quarries across the North West, including pink shap, sandstone, and granite.
These materials support uniform hydration and strong bonding within the mix, helping to maximise the benefits of fly ash while ensuring the structural integrity of the finished concrete. In essence, concrete fly ash mixes are only as good as the aggregates they’re built on.
For construction projects with sustainability or performance goals in mind, Armstrongs and our sister company AMIX offer a trusted supply chain.
Our high-quality aggregates are used in AMIX ready mix concrete, which can be tailored to include fly ash for technical or environmental specifications.
Whether you're looking to reduce embodied carbon, extend working times, or enhance durability, we can help. Contact Armstrongs for aggregate supply, or visit AMIX to enquire about fly ash concrete mixes built around your project needs.
Fly ash is used in concrete as a supplementary cementitious material. It enhances the workability of fresh concrete, improves long-term strength, and increases resistance to cracking and chemical attack. It also reduces the need for Portland cement, making concrete mixes more sustainable.
Yes, fly ash contributes to higher long-term strength in concrete. While early strength development may be slower compared to traditional mixes, concrete containing fly ash often outperforms standard mixes over time due to its pozzolanic reaction and densifying effect.
Fly ash is typically used as a partial replacement for cement, not a full substitute. Depending on the application, fly ash can replace up to 30% (and sometimes more) of the cement content in a mix. This reduces the carbon footprint while still achieving strong, durable concrete.
Fly ash enhances durability by reducing permeability, which helps protect the concrete against water ingress, sulphate attack, and alkali-silica reaction. These benefits make fly ash concrete well-suited to infrastructure and structural projects where longevity matters.
Class F fly ash has low calcium content and is known for its long-term strength and resistance to chemical attack. Class C fly ash contains more calcium and has both cementitious and pozzolanic properties. In the UK, Class F is more commonly used in construction.
Yes. Fly ash is a recycled industrial by-product, so using it in concrete helps divert material from landfill and lowers the demand for carbon-intensive cement. It’s a key ingredient in more sustainable construction practices.
Fly ash is a proven material that brings both performance and sustainability benefits to modern concrete construction. From improving long-term strength to enhancing durability and workability, its role in concrete is well-established.
At Armstrongs, we’re proud to support these advancements with a reliable supply of high-quality aggregates. Whether you’re sourcing raw materials or working with bespoke concrete mixes from AMIX, we help ensure your project is built on solid ground.
To learn more about fly ash in concrete or to discuss your aggregate requirements, get in touch with Armstrongs today.
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