Fatigue performance evaluation of asphalt mixtures based on energy-controlled loading mode

Loading mode plays a key role in the fatigue performance evaluation of asphalt mixtures. However, the stress-controlled mode and strain-controlled mode cannot reflect the pavement structure loading conditions. In this paper, a simplified pavement analysis model was designed to analyze the loading conditions of pavement structure, and the energy-controlled mode was put forward. The improved 4PB beam fatigue test procedures were proposed to achieve the energy-controlled mode. And the traditional 4PB beam fatigue tests were also conducted under stress-controlled mode and strain-controlled mode for comparative analysis, respectively. Results show that stress-controlled mode and strain-controlled mode can only reflect two kinds of critical loading conditions in the pavement structures, and do not have universal applicability. An intermediate loading condition that the stored energy approximately remains constant is found. The energy-controlled mode can be achieved well by improved test procedures. And the fatigue life Nf of asphalt mixtures measured under energy-controlled mode falls in between fatigue life Nf that is measured based on the stress-controlled mode and strain-controlled mode. The test results coincide with the theoretical analysis of simplified pavement analysis model. Therefore, the energy-controlled mode is more suitable to evaluate the fatigue performance of asphalt mixtures.