Dissipated Energy Approach to Study Hot-Mix Asphalt Healing in Fatigue

Abstract

The healing phenomenon has been noted by pavement engineers for years, but its relation to hot-mix asphalt (HMA) fatigue behavior is still far from clear. This study conducted an analysis of healing and HMA fatigue behavior by introducing a specifically designed fatigue-healing test. These results help explain the differences in fatigue behavior at normal and low strain levels. An approach using the ratio of dissipated energy change, which is based on energy concepts, is used in this study. The results show that healing does exist, and its effect on fatigue life can be indicated by an energy recovery per second of rest period. The effect of healing is more prominent at low strain levels or in very long rest periods. At low strain conditions, the dominance of healing compared with the very low external load damage, considering the energy equilibrium, can result in full damage recovery. This full recovery of energy explains the existence of a fatigue endurance limit, below which HMA materials tend to have extraordinarily long fatigue lives that, as is shown, can be related to healing. The testing conducted clearly shows why polymer modification may extend the fatigue life in the field even though laboratory testing may show minimal differences compared with the neat binder test results.

Identifying fatigue failure in asphalt binder time sweep tests

“…The Ratio of Dissipated Energy Change (RDEC) approach was proposed as an improved method for defining fatigue failure on the basis of dissipated energy evolution in fatigue tests [23]. The RDEC is defined as Eq.…”

“…However, this stiffness reduction approach to defining fatigue failure has been challenged because it is arbitrary, without any theoretical or phenomenological justification. Dissipated energy concepts have been used as the basis for alternative, more fundamental, definitions of fatigue failure, including the Dissipated Energy Ratio (DER) [11][12][13][14][15][16][17][18][19][20] and ratio of Dissipated Energy Change (RDEC) [21][22][23][24][25]. Another popular approach for defining the fatigue failure of asphalt materials is to use phenomenological parameters which correspond to marked changes in damage evolution.…”

Energy approach for the fatigue of thermoviscoelastic materials: Application to asphalt materials in pavement surface layers

“…[18], who defined the RDEC ratio of dissipated energy change, given that RDEC eliminates the energy that dissipates in other forms without causing damage. This definition provides a true indication of the damage incurred by the mixture from one cycle to the next through comparing energy level during the previous cycle and then determining how much damage has been caused.…”

“…Carpenter and Shen [18] assigned the value of RDEC during the steady-state fatigue crack propagation zone (Stage II) as the plateau value (PV) and moreover proposed that this value be used as a failure criterion insensitive to loading mode.…”

“…Guzlan and Carpenter [16], Shen and Carpenter [17] and, lastly, Carpenter and Shen [18] have used the following model to compare PV with the number of load cycles to failure:…”