The air-permeability Blaine apparatus is primarily a means to draw a specific amount of air through a ready cement bed with definite porosity. It works by drawing in a specific amount of air through a cement bed with a definitive porosity measurement. The size and number of pores in a pre-set bed with an absolute porosity value. It is a particle size function and determines the airflow rate through the bed. The procedure is outlined as Method A in ASTM C204 and AASHTO T153.