scope:

This test method covers the determination of characteristics of the air-void system of fresh concrete using a sample of mortar. Spacing factor, specific surface, and entrained air content are determined by capturing air bubbles released from a mortar sample.

The sample will only be representative of the depth of the concrete within approximately 60 mm (2.5 in.) below the level at which the sampling is begun. This method is applicable to fresh concrete with a minimum slump of 10 mm (0.4 in.) and air content between 3.5 and 10 percent by volume. Only air voids less than 3 mm (0.1 in.) in diameter are measured by this method.² The test must be performed in sheltered, stable conditions.

The values stated in SI units are to be regarded as the standard.

This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

The quality of the results produced by this standard are dependent on the competence of the personnel performing the procedure and the capability, calibration, and maintenance of the equipment used. Agencies that meet the criteria of R 18 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with R 18 alone does not completely assure reliable results. Reliable results depend on many factors; following the suggestions of R 18 or some similar acceptable guideline provides a means of evaluating and controlling some of those factors.