AASHTO T 326-22 PDF

This method describes the determination of the loose uncompacted void content of a sample of coarse aggregate. When measured on any aggregate of a known grading, void content provides an indication of the aggregate’s angularity, sphericity, and surface texture compared with other coarse aggregates tested in the same grading.

Three procedures are included for the measurement of void content. Two use graded coarse aggregate (standard grading or as-received grading), and the other uses several individual size fractions for void content determinations:

• Standard Graded Sample (Method A)—This method uses a standard coarse aggregate grading that is obtained by combining individual sieve fractions from the maximum density curve drawn from the maximum coarse aggregate size.
• Individual Size Fractions (Method B)—This method uses each of three coarse aggregate size fractions: (a) 19 mm (3/4 in.) to 12.5 mm (1/2 in.); (b) 12.5 mm (1/2 in.) to 9.5 mm (3/8 in.); and (c) 9.5 mm (3/8 in.) to 4.75 mm (No. 4). For this method, each size is tested separately.
• As-Received Grading (Method C)—This method uses that portion of the coarse aggregate retained on the 4.75-mm (No. 4) sieve.