AASHTO TP 75-08 PDF

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. The test must be performed in sheltered, stable conditions.