Material nonlinearity in asphalt binder fatigue testing and analysis

Publication date: 5 November 2017
Source:Materials & Design, Volume 133
Author(s): Farinaz Safaei, Cassie Castorena
Fatigue cracking is a primary distress in asphalt pavements caused by the accumulation of damage under repeated traffic loading. Asphalt binder is the weakest constituent of asphalt mixture. Therefore, the inherent fatigue resistance of the asphalt binder contained within the pavement is anticipated to influence pavement performance. The simplified viscoelastic continuum damage (S-VECD) model has been applied to predict fatigue life of asphalt binders under varying loading and thermal conditions using time sweep and linear amplitude sweep (LAS) test results. The majority of past efforts using S-VECD analysis protocol have neglected the effects of material nonlinearity and attributed all material integrity loss to damage for the sake of simplicity. Herein, experimental and analytical methods are evaluated for delineating damage and nonlinearity in fatigue testing of asphalt binder. None of the experimental methods evaluated enabled accurate separation of damage and nonlinearity at the high strain amplitudes included in LAS tests. Therefore, an analytical method using S-VECD modeling was proposed to back calculate nonlinear dynamic shear moduli from LAS test results. Results can be used to generate a nonlinear S-VECD model which allows for improved fatigue life predictions.

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