Fatigue tests and damage analyses in modified binders and gap-graded asphalt mixtures with Reacted and Activated Rubber

Fatigue tests and damage analyses in modified binders and gap-graded asphalt mixtures with Reacted and Activated Rubber – RAR

Lopes, Letícia Nunes / de Farias, Márcio Muniz / de Mello, Luiz Guilherme Rodrigues

Abstract

Several types of modifiers are currently studied, and among them, polymers and ground scrap tyre rubber stand out. The Reacted and Activated Rubber (RAR) is a new type of asphalt rubber that improves the engineering properties of the binder and mixtures. This research studied the rheological behaviour and fatigue performance of binders and gap-graded mixtures with RAR in quantities of 25% and 30%. The rheological characterisation tests were based on the Linear Viscoelasticity Theory and the principle of time-temperature superposition, which made it possible to elaborate the master curves. The fatigue performance was evaluated based on Continuum Damage Theory (CDT), getting the C-D curves and, in classic approach, getting the traditional Whöler curves. The tests on the binders were performed using the Dynamic Shear Rheometer (DSR) and asphalt mixtures tested in the Four-Point Bending (4PB) beam equipment. Modifications in AC 50/70 by RAR resulted in increased in PG, in softening point, rotational viscosity and density, and it reduced the penetration. Lower susceptibility to the frequency and temperature conditions of AB-R30 resulted in high fatigue life due to less sensitivity to the damage parameter. Comparison between the 4PB tests results of RAR produced mixtures tested at 20°C (MAB-R-25 and MAB-R30-1) and a field blend (MAB-RJ-122), expressed that the RAR modified mixtures exhibited superior fatigue life to the field blend, obtaining the MAB-R30-1 mix the highest performance. Tests with different temperatures for the same composition (MAB-R30-1, MAB-R30-2 and MAB-R30-3) and the same temperature for different compositions (MAB-R25 e MAB-R30-1) showed α parameter (CDT approach, C-D curves) with the similar behaviour of the parameter k₂ (traditional approach, Whöler curves). Analysing the results, considering the research conditions (base binder, temperatures, tests, and methodologies performed) binder and mixture modifications using 30% RAR, proved to be more satisfactory.