Fatigue Evaluation in Hot and Warm Mix Asphalts Based on Dissipated Energy

Warm mix asphalts (WMA), because of their low production and compact temperatures, may have different behaviors in long term. In the present work, the energy-based criteria along with the ۵۰% reduction in initial stiffness (Nf۵۰%) using four-point bending test under controlled-strain conditions of ۱۰۰۰ microstrain were applied to compare the prepared two warm mix and HMA samples. All these criteria illustrate properly the effect of mix asphalt properties (additive type) on its fatigue performance. A noteworthy point in this regard is the difference between Nf۵۰% values of the studied samples with the real failure point. For HMA and zycotherm WMA (ZWMA), loading cyclic number at the failure moment occurs almost ۸۰% higher than the fatigue life estimated using Nf۵۰% while for Sasobit WMA (SWMA) this value is declined to ۲۸%. The RDEC method, compared to other methods, indicated the maximum fatigue life and consistency with the failure point. Comparing the energy-based methods with Nf۵۰% method revealed that ERR, ERR&B, and ERP have the maximum consistency with fatigue life in terms of ۵۰% reduction in initial stiffness. For SWMA, the fatigue life at Nf۵۰% was larger than that of various energy-based methods but almost equal to that of the RDEC method. However, for two WMA mixes prepared using ZWMA and HMA, all energy methods revealed a fatigue life longer than that of Nf۵۰%.

Keywords:

Fatigue life , Dissipated Energy , Rate of Dissipated Energy Change (RDEC) , ۵۰% Reduction in Initial Stiffness (Nf۵۰%) , Warm Mix , Warm Additive