Fatigue Endurance Limit for Highway and Airport Pavements

Abstract

The existence of a fatigue endurance limit has been postulated for a considerable time. With the increasing emphasis on extended-life hot-mix asphalt pavement, or perpetual pavement, verification of the existence of this endurance limit, a strain below which none or very little fatigue damage develops, has become a substantial consideration in the design of these new multilayered full-depth pavements. Fatigue data are presented that were collected on a surface mix and a binder mixture tested for an extended period from 5 million to 48 million load repetitions at strain levels down to 70 microstrain. The fatigue results are analyzed in the traditional manner and using the dissipated energy ratio. This analysis shows that there is a difference in the data at normal strain levels recommended for fatigue testing and at the low strain levels. This difference cannot substantiate an endurance limit using traditional analysis procedures, but the dissipated energy approach clearly shows a distinct change in material behavior at low flexural strain levels, which supports the fact that at low strain levels the damage accumulated from each load cycle is disproportionately less than what is predicted from extrapolations of fatigue testing at normal strain levels. This reduced damage may be attributed to the healing process. The conclusion of this study is that laboratory testing can verify the existence of a fatigue endurance limit in the range of 90 to 70 microstrain below which the fatigue life of the mixture is significantly extended relative to normal design considerations.

Mechanical performance of asphalt mixtures modified by bio-oils derived from waste wood resources

“…Some fatigue models uses dissipated energy theories and proposed that there is a relation between the fatigue life and the dissipated energy [52][53][54]. In the four-point beam fatigue test, energies were dissipated during every flexural bending cycle because of the viscoelastic properties of asphalt mixtures.…”

Fatigue life prediction of asphalt concrete pavement using a harmony search algorithm

“…In terms of the fatigue cracking modeling based on APT, two common methods for determining crack failure are considered, as follows: (1) determine the number of repetitive loads at the instant the crack initiates on the surface of the AC pavement, thus defining the fatigue life (Newcomb, 1999); and (2) determine the number of repetitive loads on the asphalt mixture at the point when the stiffness of the asphalt mixture reaches 50% of the initial stiffness through a fatigue test, thus also defining the fatigue life (Carpenter et al, 2003).…”

Estimation of the fatigue endurance limit of HMAC for perpetual pavements

“…According to the definition of R initial , the expression of R limit is given by: (5) where, ε limit is the fatigue endurance limit [m/m], which is the amplitude of the strain level that can be applied to the material without causing fatigue failure; S limit , σ limit and f t,limit are the initial stiffness, the initial stress and the tensile strength, all in [MPa], of the specimen under the strain level of ε limit , respectively. From Fig.6, it can be seen that the initial stiffness is not affected too much by the strain level and fluctuates around its mean value.…”

“…The principle of FEL has been proved [4,5] and normally assessed through various fatigue tests in the lab. However, these fatigue tests are too costly and time consuming.…”