In accordance with previous studies [21,22], air void content in the present study was targeted at 4%. Based on the test results, in order to achieve 4% porosity or less, approximately 6% (or higher) asphalt binder needs to be included in A-AC, while about 4.8% (or higher) asphalt binder is required in AC without fibers. The standards of ASTM D2041 [23] recommend an optimum binder content of 5.77% to have a 4% air void con- tent in AC. This is higher than the binder content of AC, but lower than that of A-AC because the fibers in the A-AC increased the air void content in the mixture. Therefore, to achieve the tar- geted 4% air void content herein, a 4.8% asphalt binder was adopted for the plain AC, whereas a 6% asphalt binder was used for A-AC. In addition, to investigate the effects of air void con- tent on several fundamental properties of AC with amorphous metallic fibers (as discussed in later sections), two additional asphalt binder contents of 5.5% (smaller than 6%) and 6.5% (higher than 6%) were adopted.