Viscoelastic Master Curve Transformation and Comparison of Asphalt Mixture Under Dynamic and Static Loads
In order to compare the relaxation modulus of asphalt mixture derived from modulus master curves under dynamic and static loads respectively,5 kinds of asphalt mixtures are selected to undertake the dynamic modulus and creep compliance tests.Firstly,based on the time-temperature equivalent principle,the master curves of dynamic modulus and creep compliance of asphalt mixtures are obtained by Sigmoid function and WLF equation fitting with dynamic modulus values at different frequencies and temperatures and creep compliance values at different temperatures and stress levels obtained by experiments.The generalized Maxwell and generalized Kelvin models are used to simulate the relaxation and creep properties of asphalt mixture respectively.Finally,the mutual conversion among viscoelastic parameters is realized by using Laplace transform and Prony series expressions.The result shows that the inter-conversion values of dynamic modulus and creep compliance master curves are basically consistent with the test results,and the relaxation modulus master curves transformed by creep compliance under different stress loads has the same form and different curvature as that transformed by dynamic modulus.The applied load stress has great influence on creep compliance,The larger the loading stress in the time domain,the smaller the creep compliance.In the lower time domain,the creep compliance values have little difference under different stress conditions with the increase of time domain,the smaller the loading stress,the greater the increase of creep compliance master curves.The relaxation modulus,derived from creep compliance under 0.5 MPa loading,fit well with the value transformed by dynamic modulus.In the frequency domain of 10―4-10+3s,the difference of relaxation modulus obtained by dynamic modulus and static compliance is less than 15%for all the asphalt mixtures.For simplicity,the creep compliance test under 0.5 MPa could be used to substitute the dynamic modulus test in practical engineering,where the calculated relaxation modulus in the frequency domain of 10―4-10+3 s is preferred.
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