Influence of transient effects for analysis of complex modulus tests on bituminous mixtures

摘要

Accurate experimental results and rheological simulations of complex modulus tests on bituminous mixtures are presented. The linear viscoelastic (LVE) asymptotic expression (obtained in the small strain domain) of the visco-plastic model Di Benedetto-Neifar, which corresponds to the Generalised Kelvin-Voigt model, is used to simulate the behaviour of tested mixtures. Its calibration considering 40 elements is made from the 2S2P1D model (two springs, two parabolic elements and one dashpot) with a continuum spectrum, also developed at the Laboratoire Genie Civil Batiment - Laboratoire de Tribologie et Dynamique des Systemes laboratory of the Ecole Nationale des Travaux Publics de l'Etat. Rheological simulations considering perfect sinusoidal signals loading and experimental loading allow evaluating transient effects existing at the beginning of the tests. It is shown that the four first cycles must be discarded, when analysing test data, to obtain correct complex modulus values. During these cycles a transient phase, which is quantified, exists. In addition, it is shown that the linear model correctly approximates the behaviour of bituminous mixtures but nonlinearities and/or biased effects can also be observed. The number of cycles applied during tests must then remain small for a correct LVE characterisation of bituminous mixtures.