Linear viscoelastic properties and fatigue S-VECD based evaluation of polymer-modified asphalt mixtures

Abstract

Direct tensile fatigue tests associated with the simplified continuous damage viscoelastic model (S-VECD) have proven to be an effective tool for evaluating fatigue in asphalt materials. Thus, this study evaluated the fatigue damage of asphalt mixtures modified by the addition of polymer based on the results of the direct tensile fatigue test using the S-VECD model. Three asphalt mixtures were produced: a control asphalt binder with 50/70 penetration, a polymer-modified styrene-butadiene-styrene (SBS) asphalt binder, and a mixture produced with a modified asphalt binder (composed of 98.38% control + 1.26% Ethylene Methyl Acrylate and Glycidyl Methacrylate (EMA-GMA) + 0.21% High-Density Polyethylene (HDPE) + 0.15% Polyphosphoric Acid (PPA116%)). The binders were evaluated for physical and rheological properties, and fatigue using the Linear Amplitude Sweep (LAS) test, applying the S-VECD model. Asphalt mixtures were evaluated for stiffness using tensile strength, resilient modulus and flow number tests. The viscoelastic linear behaviour (LVE) was characterized based on the dynamic modulus test and the fatigue performance was evaluated from the uniaxial direct traction test with the application of the S-VECD viscoelastic damage model. The results of the LAS test indicated that the modified binder presented the best fatigue performance, being classified according to the binder fatigue factor (FFB) as excellent. Mixtures with binders modified by polymers showed the highest values in mechanical performance tests. As for the LVE behaviour, the mixture with the modified binder showed the expected behaviour, with higher dynamic modulus values at high temperatures (low reduced frequencies), and the lowest modulus values at lower temperatures (high reduced frequencies). In addition, for the entire spectrum of frequencies and temperatures, the modified mixture presented the lowest values of phase angle, indicating more elastic and less viscous behaviour. From the direct tensile test, based on the GR failure criterion, the modified mixture showed better fatigue performance, with a higher value of the Fatigue Factor of the Mixture (FFM). Based on the DR failure criterion, from the Sapp damage capacity, mixtures with polymers were classified with the best performances concerning fatigue. Therefore, the use of polymer-modified binders promoted asphalt mixtures with better fatigue damage performance.