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Concrete & Masonryaka: AEAaka: air-entrained concrete

Air Entrainment

In Plain English

Tiny air bubbles mixed into concrete that protect it from cracking when water freezes and expands inside it.

Definition

The intentional introduction of tiny, uniformly distributed air bubbles into concrete through the use of an air-entraining admixture. Entrained air improves resistance to freeze-thaw damage by providing space for water to expand when it freezes. Exterior flatwork exposed to freezing temperatures typically requires 5-7% entrained air content.

Why It Matters in Bidding

Air entrainment is a spec-driven requirement that estimators must catch in the concrete section, because the air-entraining admixture adds cost and the required air percentage affects mix design pricing from the ready-mix supplier. Missing an entrained-air callout on exterior flatwork in a freeze-thaw climate can lead to failed acceptance testing, rejected pours, and costly removal and replacement that erase the bid margin.

Example

Bidding an exterior parking apron in a northern climate, the estimator confirms the spec requires 6% entrained air and prices the admixture into the ready-mix quote so the field crew is not surprised at the slump and air test.

Related Terms

AdmixtureFlatworkCuringWater-Cement Ratio

Frequently Asked Questions

The air-entraining admixture is a small added cost per cubic yard, but the larger impact is on mix design and placement. Entrained air increases workability, which can reduce water and labor, yet it slightly lowers compressive strength, sometimes requiring more cement. Confirm the required air percentage so your ready-mix quote reflects the correct mix.
Specs typically require it for exterior concrete exposed to freezing and de-icing chemicals, such as sidewalks, slabs, curbs, and pavements in cold climates. Interior slabs rarely need it. Read the structural and concrete sections carefully during takeoff, because the requirement and the target air percentage vary by exposure class.
A testing agency or the concrete subcontractor performs air-content tests on fresh concrete at delivery, often alongside slump and cylinder sampling. If results fall outside the specified range, the load can be rejected. Estimators should account for testing coordination and the risk of rejected loads when scoping cold-weather exterior pours.

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