ASTM C260/C260M
Standard Specification for Air-Entraining Admixtures for Concrete
The admixtures that deliberately create microscopic air bubbles in concrete, which is the primary defense against freeze-thaw damage.
Who needs it
Batch plants, admixture suppliers, and anyone specifying or placing exterior concrete in a freezing climate.
What the test involves
It sets the performance a product must demonstrate to be sold as an air-entraining admixture, evaluated by its effect on a reference concrete rather than by its ingredients. The bubbles it creates are far smaller than the accidental voids left by poor consolidation, and their spacing is what actually protects the paste when water inside the concrete freezes and expands. The specification also addresses effects on strength, set time, and shrinkage so the cure is not worse than the disease.
Common misconceptions
- Entrained air and entrapped air are not the same thing. Entrapped voids from poor vibration do not provide freeze-thaw protection.
- Air content is not fixed once batched. Over-troweling, long pump lines, and hot concrete can all reduce the air that reaches the finished surface.
- Hard-troweling an air-entrained exterior slab is a known cause of surface delamination, which is why air-entrained flatwork is usually broom finished.
Official source
We summarize scope and purpose only. The full text belongs to the issuing body — read it at the official source. ASTM International