The beam fatigue test of hot-mix asphalt (HMA) has been used for nearly a half century.However, several conflicting results have been recently reported. This study attempts tooptimize the test conditions such as waveform type (haversine vs. sinusoidal), incorporating restperiods between loading cycles and the effect of rest period on the healing of the HMA tominimize (eliminate) gross errors in the data analysis of the fatigue test results. In the deflection7controlled haversine test (ASTM D-7460) permanent deformations lead to a new equilibriumneutral position of the beam and the force output follows a sinusoidal waveform. This tends tobend the beam in both directions similar to the deflection-controlled sinusoidal test. This wouldproduce erroneous fatigue results since the test assumptions do not match the actual testconditions. In contrast, the deflection-controlled sinusoidal test (AASHTO T-321) is moreconsistent than the deflection-controlled haversine test (ASTM D-7460). When tests, with andwithout rest periods, are compared for healing type of studies, it is even more important to use adeflection-controlled sinusoidal test in order to obtain a fair comparison and accurate healingresults. Since neither the haversine waveform nor the sinusoidal waveform in the lab exactlysimulates field conditions, it is important to use a sinusoidal waveform in order to obtainconsistent results. It is recommended that ASTM changes the ASTM D-7460 designation andtest procedure to require a deflection-controlled sinusoidal waveform instead of haversine.
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