Fly Ash as Pozzolan: Benefits of Using This Underused Component in Concrete Construction

You might have never heard of fly ash; however, did you know this industrial by-product can substitute cement? But what exactly is it? In this blog, we’ll explore the benefits of using fly ash and how to ensure you use it correctly for the best results.

What is Fly Ash? 

Fly ash is a pozzolan used in concrete to improve workability and decrease water demand. It is also used as an additive to Portland cement to create more durable concrete. 

• Fly ash is a by-product of burning coal and is composed of fine particles of unburned carbon, silica, alumina, and other minerals.
• It comprises fine particles collected from coal-fired power plants' flue gases.
• Fly ash is a great addition as it can improve concrete’s characteristics, like,
• Strength 
• Durability 
• Workability 
• Using fly ash as a pozzolan in concrete construction has numerous benefits.  
• Replacing some of the cement in a concrete mix with fly ash reduces the energy and resources needed to produce the concrete.

What is Pozzolan?

Pozzolan is a siliceous or siliceous-aluminous material that forms cementitious compounds when combined with calcium hydroxide. It is typically derived from volcanic ash or industrial waste products such as fly ash and can partially replace Portland cement.

How Does it Affect Concrete?

• Pozzolan-based concrete is often used in construction projects where high weathering or exposure to chemicals is expected.
• Using pozzolan can help reduce a project's carbon footprint by reducing the amount of Portland cement with more sustainable materials.
• Fly ash can reduce the amount of energy needed to produce concrete and can help reduce the amount of carbon dioxide emissions associated with concrete production.
• Fly ash can also help reduce the water needed to produce concrete. 
• Fly ash can help reduce the amount of dust and other particulate matter that is released into the air during concrete production.
• Using fly ash as a pozzolanic material in concrete construction can help reduce the environmental impact of concrete production.

Properties of Fly Ash

Fly ash is a by-product containing various compounds, including silicon dioxide, aluminium, calcium, and iron oxide. When used as a pozzolan in concrete construction, fly ash reacts with calcium hydroxide to form calcium silicate hydrate (CSH), the main binding agent in concrete.

Using fly ash as a pozzolanic material can result in several important benefits for concrete construction, including, 

• Improved strength
• Improved durability
• Reduced permeability
• Increased chemical resistance
• Improve workability 
• Recuse costs 
• Recuse carbon footprint

How Can it be Used? 

Fly ash is usually added to the concrete at the mixing stage and can be either dry or wet. 

• When added in dry form, it is usually mixed with the dry ingredients of the concrete mix, such as cement and sand, before any water is added. 
• When wet, it is usually added to the mix with water. 
• The amount of fly ash used in the mix depends on the type of concrete being produced.
• Generally, fly ash is recommended to make up between 10 and 30 per cent of the total cementitious material in the mix.
• The rest of the cementitious material is usually made up of Portland cement. 
• When mixed with concrete, fly ash helps reduce the water needed to produce a workable mix. 
• Fly ash also helps reduce the shrinkage in concrete as it cures. 
• This is because it helps to fill the gaps between the cement particles, resulting in a dense concrete mix. 
• Fly ash can help reduce shrinkage cracks in concrete by up to 50%.

Benefits of Using Fly Ash in Concrete

• Improved Workability 

Fly ash particles are spherical and uniform in size, making them ideal for concrete use. The particles fill the spaces between the cement particles and improve the flow of the concrete mix.

• Decreased Water Demand 

Using fly ash in concrete can help reduce the water content of the mix without compromising workability. This can lead to a reduction in shrinkage cracking and an increase in durability.

• Increased Strength and Durability

 Adding fly ash to concrete can improve its strength and durability, making it ideal for infrastructure projects.

• Increased Resistance to Weathering

 Fly ash increases the resistance of concrete to weathering, making it ideal for exterior applications.

• Eco-Friendly

Fly ash is a by-product, and using it as a pozzolan helps reduce the environmental impact of concrete construction.

Potential Challenges of Using Fly Ash as Pozzolan

There are a few potential challenges to using fly ash as a pozzolan in concrete construction. 

• One is that fly ash can be difficult to obtain in some areas.
• Fly ash can be more expensive than other pozzolans. 
• Fly ash is sometimes difficult to work with because it is a fine powder.

Conclusion

Fly ash has proven to be a superior pozzolan for use in other building materials, making it a great choice for anyone looking for an economical and eco-friendly way to construct buildings. Its pozzolanic properties make it an excellent choice for improving the strength and durability of concrete. To learn more about building materials and construction techniques, check out the blogs and courses offered by Skill-Lync. We offer various courses in the civil domain, including  BIM, Structural design etc. Book a free demo to know more!