ously caused sufficient expansion of AC, indicating that expansion should be taken into account when amorphous metallic fibers are applied in AC in practice. Interestingly, the expansion was not significantly influenced by the amount of asphalt binder, regardless of fiber length, volume fraction, or time following the completion of specimen fabrication. The potential explanation for this observation is as follows: the volume of AC is mainly changed by temperature variation due to its high coefficient of thermal expansion. However, the temperature in the testing room was marginally changed during experiment, and it led to insignificant change of AC’s volume regardless of the amount of asphalt binder. In addition, the difference between the amounts of asphalt binder (5.0% and 5.5%) was quite small to result in obvious change in the expansion. Based on the test results, 15-mm-long amorphous metallic fibers were selected, because (even though the expansion of A- AC with 15-mm fibers exhibited similar or slightly larger expansion than the expansion of A-AC with 10-mm fibers) the fabrication of 10-mm fibers was much more difficult than the fabrication of 15-mm fibers. The use of a larger amount of fibers is more effective in improving tension-dominated crack resistance in A-AC. Since the samples with 1.5% 15-mm-long fibers exhibited a significant expansion after 2 h, the fiber volume fraction of 1% was determined in this study. Consequently, the amorphous metallic fibers with a length of 15 mm at volume fraction of 1% were included in the asphalt mixture for the A-AC samples, discussed in the following chapters.