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Entrained air also reduces scaling caused by growing and expanding salt crystals inside the concrete. Concrete becomes more susceptible to scaling when blast furnace slag or fly ash are mixed into the Portland cement. Scaling occurs when entrained air near the concrete's surface is reduced when finishing occurs too soon. Moist curing followed by air drying makes air entrained concrete more resistant to scaling from freeze thaw cycles and deicers. The best air drying occurs when concrete is poured in the spring and summer. Air entrainment with low water to cement ratio and low tricalcium aluminate increases concretes resistance to sulphates. Air entrainment increases concrete workability but reduces its strength. Increasing the volume of air in concrete reduces the amount of cement paste and water needed to bond to the aggregates. Increasing the cement volume and fineness reduces the amount of air in concrete. |
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