ASTM C948-81(2016)

Note 1: This test method does not involve a determination of absolute specific gravity. Therefore, such pore space as may be present in the specimen that is not emptied during the specified drying or is not filled with water during the specified immersion is considered “impermeable” and is not differentiated from the solid portion of the specimen for the calculations, especially those for percent voids.

Depending upon the pore size distribution and the pore entry radii of the specimen and on the purposes for which the test results are desired, the procedures of this method may be adequate, or they may be insufficiently rigorous. In the event that it is desired to fill more of the pores than will be filled by immersion, various techniques involving the use of vacuum treatment or increased pressure may be used. If a rigorous measure of total pore space is desired, this can only be obtained by determining absolute specific gravity by first reducing the sample to discrete particles, each of which is sufficiently small so that no impermeable space can exist within any of the particles.