Durability

Additional Details

While strength is an important criterion for concrete performance, it fails to give an insight into durability. Strength is only a measure of the ability to sustain loads at a given point while durability is the ability to maintain integrity and strength over time. Two concrete mixes with equal strength can vary widely in their durability properties. Concrete will only be durable if the movement of aggressive chemicals within its structure is minimized. This means that it must be dense and impervious with a minimum of cracks. How does Fly Ash protect concrete? The incorporation of Ashtech’s Fly Ash minimizes the water demand, reduces the bleed channels and through pozzolanic activity increases the cementitious compounds, all of which increase the concrete density. These factors yield concrete of low permeability with low internal voids, which dramatically improves the resistance against chloride ingress, sulphate attack and corrosion of the steel reinforcement. The benefits of the low water demand of Fly Ash concrete is of prime importance particularly in combination with a low water / cement ratio – lower water allows lower cement for a given strength level. This allows lower heat development, porosity and shrinkage of the concrete. The reduced cement content in Fly Ash concrete lowers the heat of hydration, which is especially beneficial in mass concrete applications. Reduced temperature gain results in reduced thermal shrinkage and less possibility of thermal cracking. In reduced alkali-silica reactivity, Fly Ash has the ability to react with alkali hydroxides in Portland cement paste, making these unavailable for reaction with reactive silica in certain aggregates. Any risks of alkali silica reaction are significantly reduced if not completely eliminated. The use of Ashtech’s Fly Ash to improve the technical properties of the hardened concrete has become a standard, particularly in hot and aggressive environments. Consultants and Engineers alike have recognized this with the result that Ashtech’s Fly Ash has been successfully specified and used in some of the most prominent structures in India and the Middle East, where we have worked in close partnership and agreement with ash resources of South Africa.