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.
Highlights
Asphalt mixes (AM) have a linear viscoelastic (LVE) behaviour in the small strain domain [1]Cyclic tension–compression tests are traditionally used to determine the LVE properties of AM that are strongly dependent on frequency and temperature
Numerical frequency response functions (FRFs) were calculated with the finite element method (FEM) considering linear viscoelastic behaviour and the dynamic test boundary conditions
The second step, which ismeasured the sameFRFs for the twodynamic proposedtests methods, in using the complex second step, which is the same for the two proposed methods, consists in using the complex modulus modulus values determined in the first step at each temperature to fit a 2S2P1D model and a WLF law values determined thebehaviour first stepofatthe each temperature to fit a is2S2P1D
Summary
Asphalt mixes (AM) have a linear viscoelastic (LVE) behaviour in the small strain domain [1]. Cyclic tension–compression tests are traditionally used to determine the LVE properties of AM that are strongly dependent on frequency and temperature. These tests require expensive experimental devices such as hydraulic presses and are not applicable in situ. In the case of LVE materials, dynamic tests could be a great alternative to conventional cyclic tension–compression tests. Characterizing accurately the LVE behaviour of AM from FRFs is not possible through a simplified analysis [22] and it requires an elaborate approach. Experimental complex modulus values obtained from tension–compression tests and back-calculated from FRFs with the two proposed methods were used to fit the 2S2P1D model and the Williams-Landel-Ferry (WLF) constants simulating the global LVE behaviour of the material in each case. Data from tension–compression tests are compared with results from the two methods of back-analysis of the dynamic tests
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