Your guide to Civil Engineering basics: Fly Ash Concrete

Fly Ash Concrete: Reduced Efforescence

What is Fly Ash	Historical Background	Chemical Nature	Classification
Chemical Composition	Mechanical properties	Benefits	High Volume Fly Ash
Need for extending Strength Specifications to beyond 28 days		Restraints on use of Fly Ash in Highway Constructions

Most people have seen concrete or masonry walls or slabs with the white, chalky surface coating or streaks called efflorescence.

Efflorescence is caused by the face of the concrete being wetted and dried repeatedly, or by the movement of water vapor from the damp side of the concrete to the dry side through the capillaries (voids), drawing out the water soluble lime from the concrete, block or mortar.

Fly ash chemically reacts fly ash concrete: reduced efforescence

with this lime to create more CSH, the same “glue” produced by the hydration of cement and water, thereby closing off the capillaries that allow the movement of moisture through the concrete. The result is concrete that is less permeable, as witnessed by the reduction in efflorescence.

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Concrete-Techgroup thanks Headwaters Resources , USA for granting them permission to use their resources in developing this article.