What is meant by air-entrained concrete?
What is meant by air-entrained concrete?
Air-entrained concrete contains billions of microscopic air cells per cubic foot. These air pockets relieve internal pressure on the concrete by providing tiny chambers for water to expand into when it freezes.
What is the benefit of air-entrained concrete?
The benefits of entraining air in the concrete include increased resistance to freeze-thaw degradation, increased cohesion (resulting in less bleed and segregation) and improved compaction in low-workability mixes. The volume of air entrained depends on the application and the mix design.
What is the meaning of air entrainment?
Air entrainment, or free-surface aeration, is defined as the entrainment/entrapment of un-dissolved air bubbles and air pockets that are carried away within the flowing fluid. The resulting air–water mixture consists of both air packets within water and water droplets surrounded by air.
How is air entrained concrete made?
Air entrainment in concrete is the intentional creation of tiny air bubbles in a batch by adding an air entraining agent during mixing. A form of surfactant (a surface-active substance that in the instance reduces the surface tension between water and solids) it allows bubbles of a desired size to form.
How can the air-entrained concrete improve workability?
Effects on Concrete Properties — Air entrainment increases the workability of fresh concrete. The tiny bubbles in the cement act like fine aggregates and reduce the interactions between solid aggregates. The improvement in workability leads to use of air entrainment admixtures even when freeze-thaw is not a problem.
Is air entrained concrete necessary?
It is important to use air entrained concrete to avoid cracks in the concrete which later leads to increased deterioration of the structure. Technical Information: For freeze-thaw protection, the air content of a concrete mix will typically be in the 5-7% range.
Can you trowel air entrained concrete?
When finishing air-entrained concrete, less is more. Hard-troweled surfaces and air-entrained concrete don’t mix. If you need to entrain air—that is, if the concrete will experience cycles of freezing and thawing while wet—you should do as little finishing as possible.
Is air entrained concrete stronger than non air entrained concrete?
Concrete with entrained air will have a lower strength than the same mix without entrained air, but the concrete can attain strengths required for most purposes by an increase in the cementitious factor of the mix or by reducing the water content.