Determining the air-void distribution in fresh concrete with the Sequential Air Method

- A test to measure the size and spacing of air voids in fresh concrete is presented.
- The test results correlate with both the Spacing Factor and freeze-thaw durability.
- The variance of the test is similar to the Spacing Factor and freeze-thaw durability.
- The test can be completed in the field with simple equipment in less than 10 min.

A new approach is presented to determine the air void size and spacing in fresh air entrained concrete by measuring the change in response of the concrete to a series of sequential pressures. This information is used to calculate a parameter called the Sequential Air Method (SAM) Number. Comparisons are made to hardened air void analysis (ASTM C457) from laboratory and field tests for 303 mixtures as well as rapid freeze-thaw testing (ASTM C666) for 68 mixtures to the SAM Number with over 85% agreement. Furthermore, the SAM Number showed a higher correlation to rapid freeze-thaw testing than current recommendations for the Spacing Factor. The variability of the SAM Number is compared to other direct and indirect measurements of air void size and spacing. Finally, several applications of the method are discussed along with guidance on how to specify the method.