Characterization of Asphalt Mixes Behaviour from Dynamic Tests and Comparison with Conventional Cyclic Tension–Compression Tests

Abstract

In the presented research, conventional cyclic tension⁻compression tests and dynamic tests were performed on two types of asphalt mixes (AM). For the tension⁻compression tests, the complex modulus was obtained from the measurements of the axial stress and axial strain. For the dynamic tests, an automated impact hammer equipped with a load cell and an accelerometer were used to obtain the frequency response functions (FRFs) of the specimens at different temperatures. Two methods were proposed to back-calculate the complex modulus from the FRFs at each temperature: one using the 2S2P1D (two springs, two parabolic elements and one dashpot) model and the other considering a constant complex modulus. Then, a 2S2P1D linear viscoelastic model was calibrated to simulate the global linear viscoelastic behaviour back calculated from each of the proposed methods of analysis for the dynamic tests, and obtained from the tension⁻compression test results. The two methods of analysis of dynamic tests gave similar results. Calibrations from the tension⁻compression and dynamic tests also show an overall good agreement. However, the dynamic tests back analysis gave a slightly higher value of the norm of the complex modulus and a lower value of the phase angle compared to the tension⁻compression test data. This result may be explained by the nonlinearity of AM (strain amplitude is at least 100 times smaller for dynamic tests) and/or by ageing of the materials during the period between the tension⁻compression and the dynamic tests.

Keywords

• asphalt mixes
• linear viscoelasticity
• complex modulus
• dynamic measurements
• tension–compression tests
• frequency response function
• back-analysis
• finite element method