Integrated viscoelastic-statistical analysis of the fatigue-critical temperature in two polymer-modified asphalt mixes

Asphalt mixes exhibit temperature-dependent behavior and inherent fatigue data dispersion, making fixed testing temperatures and Gaussian assumptions questionable, particularly for modeling fatigue-life dispersion. Furthermore, while previous studies have reported that the fatigue-critical temperature aligns with maximum viscoelastic dissipation in mixes with conventional binders, its applicability to polymer-modified asphalt mixes remains uncertain. This study aimed to identify the fatigue-critical temperature of two polymer-modified asphalt mixes and to evaluate its correspondence with the loss modulus peak, using a Weibull-based probabilistic framework. An integrated viscoelastic-statistical methodology was applied to two styrene-butadiene-styrene (SBS)-modified mixes: a road base asphalt concrete (GB) produced with a 60/85-E binder and a high-modulus mix (EME) formulated with a highly modified asphalt (HiMA) binder. Fatigue tests were conducted using a two-point bending configuration at four temperatures: 0 °C, the standardized 10 °C, and two temperatures corresponding to the peaks of the loss modulus ( E 2 ) in the Cole–Cole plane. Fatigue life data were analyzed using a three-parameter Weibull distribution with optimized parameters. The results revealed a nonlinear (U-shaped) relationship between the strain at 1 0 6 cycles ( ɛ ɛ 6 ) and temperature, with a fatigue-critical temperature of 10 °C for the investigated mixes. Under this condition, a critical elastic-viscous balance was observed, with a loss tangent close to 0.104. Weibull modeling successfully captured dispersion and asymmetry, indicating greater predictability for the EME mix. The fatigue-critical temperature for the investigated mixes did not coincide with the peak of the loss modulus ( E 2 ), indicating that maximum viscoelastic dissipation does not necessarily define the fatigue-critical condition.