Comparison between 2PB and 4PB methodology based on the Dissipated Energy Approach

Two and four point bending tests are among the most common methodologies adopted in Europe and United States for the fatigue characterization of asphalt mixes. Both tests tend to simulate the flexural stresses generated by traffic applying uniaxial rather than triaxial loading. The main differences between these procedures are: the direction of load application, the constrains and the volume of material subjected to fatigue. In this study, based on Fatigue data, the Elletipi horizontal two point bending (2PB) and a traditional four point bending (4PB) results are compared. The peculiarity of the 2PB flexural device is the horizontal position of the trapezoidal specimen during the test. All tests were performed in strain controlled conditions at different temperatures. The research focuses on the influence of the loading waveform by comparing the effects of sinusoidal and haversine loads of equivalent strain amplitudes. The Ratio of Dissipated Energy Change (RDEC) approach, based on the energy balance classical theory, was the application of choice for the analysis of results. Finally, the influence of specimen volume on fatigue resistance was assessed performing horizontal 2PB tests on trapezoidal specimens of different thickness.