Effect of binder grade on performance parameters of asphaltic concrete paving mixtures

This study explores effect of binder grade variation on the performance parameters of stiffness, fatigue, and permanent deformation using different asphaltic concrete paving mixtures. Two penetration grade binders (40/50 and 80/100), four gradations (two wearing and two base courses) and single limestone aggregate source were used. Superpave Gyratory Compactor (SGC) was employed to fabricate specimens for Dynamic Modulus |E∗| test, Repeated Load Deformation Test (Flow Number Test, FN) and Static Creep Test (Flow Time test, FT) using Asphalt Mixture Performance Tester (AMPT). The |E∗| test was carried out for a range of temperatures (4.4-54.4 °C) and a frequency sweep (25-0.1 Hz), while FN and FT tests were performed at a single effective temperature of 54.4 °C and 300 kPa stress level. The |E∗| test results were subjected to the non-linear optimization technique to develop the stress-dependent master curves which reveal that the grade of bitumen significantly influences the stiffness of mixtures. The combination of the |E∗| and the phase angle pronounced into fatigue parameter which describes the fatigue behavior of a mix, and results indicate that the softer grade translates into higher fatigue resistance and vice versa. We observe that the 40/50 binder, ​on average, is 1.8 times more rut-resistant than the 80/100 binder. Further, this study also develops a non-linear regression model to express |E∗| as a function of testing temperature, loading frequency, and mixture volumetric parameter.