Fatigue performance of asphalt mixture containing recycled materials and warm-mix technologies under accelerated loading and four point bending beam test

Using high contents of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) in pavement constructions has gained significant popularity in the recent years as a viable solution to cleaner paving material productions. The objective of this study was to evaluate fatigue cracking resistance of RAP and RAS containing asphalt paving mixtures by a bench-scale test and a full-scale test. A flexural beam fatigue test method was used for the bench-scale evaluation, while the accelerated loading facility (ALF) experimental data, obtained by the federal highway administration (FHWA) since 2013, provided the full-scale evaluation. A total of ten plant produced asphalt mixtures used for ten full-scale test lanes were collected at the time of construction and recently prepared as beam specimens for the four-point bending beam fatigue test. Two performance grades asphalt binders (PG 64-22 and PG 58-28) were used with a conventional hot-mix and two warm-mix (foaming and chemical additive) production processes. Beam fatigue tests were conducted by applying strain-controlled repeated sine waves until the beam failure occurs at 50% of the initial stiffness (Si), which were then used to evaluate the fatigue resistance of the ten mixtures. Beam fatigue and ALF test results indicated that an increase in recycled binder ratio (RBR) results in a reduced fatigue life. Use of RAS appeared to reduce the fatigue life of ALF test lane by 65%, but reduced the mixture fatigue life by only 2.3%. Using softer asphalt binder (PG58-28) improved the fatigue life of asphalt mixtures and pavements with 40% RAP, but did not improve as much when used with 20% RAS. Using the foaming warm mix asphalt (WMA) process improved the fatigue life of asphalt mixtures and pavements when used with 20% RAP. However, when used with 40% RAP, this benefit of the foaming WMA process may be reduced. The chemical WMA binder additive (Evotherm) generally did not improve the fatigue life of asphalt mixtures and pavements.