Adding fly ash to your concrete mix offers you a practical, cost-effective way to increase its strength, plasticity and durability. You'll use less cement, but actually produce a superior product.
Benefits to plastic concrete:
- Improved workability – The small, spherical shape of fly ash particles provides a “ball bearing” effect that creates a concrete paste with superior plasticity.
- Decreased water demand – Replacing cement with fly ash reduces the water demand for a given slump and, in certain situations, can even reduce drying shrinkage.
- Increased pumpability – The spherical shape of fly ash reduces internal friction, producing a mix that is easier to pump.
- Reduced segregation – Fly ash adds body to plastic-state concrete, increasing its cohesiveness.
- Less bleedwater – Fly ash's lower water content reduces bleeding.
Benefits to hardened concrete
- Increased strength – In concrete, fly ash will continue to react with available lime and alkali, causing it to gain strength beyond 28 days.
- Reduced drying shrinkage – Fly ash concrete requires less water, hence less volume lost in drying.
- Decreased permeability – Fly ash particles pack tightly. In addition, the chemical reaction between fly ash and lime forms bonds that block bleed channels and fill pore spaces.
- Resistance to sulfate attack – Fly ash combines with free lime, making it unavailable to react with sulfates that can cause expansion problems.
- Improved durability - Less free lime, greater strength and less permeability produce concrete that withstands more punishment over the long term.
- Reduced heat of hydration – Large concrete masses typically generate high internal temperatures and experience thermal cracking as a result. By replacing a portion of portland cement with fly ash, your concrete will generate less heat and thus be less prone to fractures.
- Mitigated alkali silica reaction 'ASR' – Fly ash reacts with available alkalis in the hardened cement matrix, making them less likely to react with the aggregate.
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