Study of Asphalt Aging through Beam Fatigue Test

This study investigated the effects of aging on the flexural stiffness (E) and fatigue life (N) of asphalt concrete (AC) samples. Asphalt beam samples were prepared in the laboratory and subjected to various modes of aging (e.g., field aging, oven aging, forced air aging, normal air aging) for different periods. The flexural stiffnesses of these aged samples were determined by the four-point bending test. In addition, loose asphalt mixture was subjected to short-term oven aging up to 100 h. This loose mixture was used to prepare beam samples, which also were tested in the four-point bending mode. The flexural stiffness of unaged sample was determined as a reference value. Results showed that most of the aging occurred during the initial repetition of aging. Forced air caused more aging than the other modes. Overall, aged AC samples exhibited a shorter fatigue life (i.e., smaller N-value). The correlation of fatigue life with stiffness (i.e., N–E relationship) followed the same trend for unaged samples, aged loose mixtures, and field-aged samples. The results of this study led to the proposal of a revised fatigue life model to accommodate the aging of AC.