In the publication by Brennan et al. (2000) is proposed another method of SMA design developed in Ireland. This method allows for a required discontinuous gradation of an asphalt mix between 0.6 mm and 5.0 mm sieves (for SMA 0/14) to create a strong skeleton of coarse grains. The determination of the properties of the coarse aggregate fraction (greater than 2 mm), screened out of the aggregate mix, has been recognized as the key issue, as in other methods. The density of the compacted coarse aggregate fraction is determined by vibration; a sample is tested under low pressure in the mold used during the California Bearing Ratio (CBR) test by placing it on a vibration table commonly used for compacting samples of ready-mix concrete. The sample is compacted to the refusal density with the use of variable values of amplitude until the moment particles start crushing (the amount of fine particles smaller than 2 mm is about 1%).
Having already obtained information about the density of the coarse-aggregate fraction and the target content of air voids in the SMA samples, one can use the formulas detailed by Brennan et al. to calculate the necessary content of the coarse — aggregate fraction for the mix to fulfill all determined requirements (e. g., void content).
