Experimental Research On Triaxial Dynamic Modulus Of Asphalt Mixture

The modulus of the material is a key parameter for the design and mechanical analysis of the pavement structure.How to obtain an accurate material modulus is one of the difficulties in the current research.At present,the assumption that the asphalt mixture is regarded as a linear viscoelastic material ignores the nonlinear characteristics of the material,Resulting in a large difference between the value of the modulus of the asphalt mixture and the actual results.In order to characterize the nonlinear behavior of asphalt mixture materials and obtain accurate material modulus,the dynamic mechanical properties of asphalt mixtures and the nonlinear characteristics of materials were studied through the asphalt mixture dynamic modulus test.First,based on the triaxial confining pressure test,the dynamic mechanical properties of the asphalt mixture were studied.By carrying out the triaxial dynamic modulus test of asphalt mixture,the influence of different factors on the dynamic modulus and phase angle of asphalt mixture was analyzed,and the main curves of triaxial dynamic modulus and phase angle were constructed based on Boltzmann and Guassamp function models.The results show that the increase of the test temperature or the decrease of the scanning frequency will increase the dynamic modulus of the asphalt mixture,and vice versa.In the high-temperature or low-frequency region,asphalt mixture has a significant load dependence,and the compression load mainly plays a role in hardening the asphalt mixture.The properties of the material itself can also affect the dynamic mechanical properties of the asphalt mixture.Secondly,based on the two-point bending test,the dynamic mechanical properties of the asphalt mixture were studied.Through the dynamic modulus test of asphalt mixture,the influence of different factors on the dynamic modulus and phase angle of asphalt mixture was analyzed,and the main curves of dynamic modulus and phase angle were constructed.The results show that the increase of the test temperature or the decrease of the scanning frequency will increase the dynamic modulus of the asphalt mixture,and vice versa.In the high-temperature or low-frequency region,asphalt mixtures have significant load dependence,and the asphalt mixtures under bending load play a softening role.Thirdly,the difference of asphalt mixture dynamic modulus test under two load modes is compared.The results show that the main curve of the three-axis dynamic modulus and phase angle of the asphalt mixture is more complete.In the high-temperature and low-frequency area,the three-axis dynamic modulus is significantly greater than the bending-tension dynamic modulus,and the phase angle is the opposite.The dynamic modulus test method has its own advantages and disadvantages,and the test method must be selected according to the corresponding requirements.Finally,the internal relationship between the nonlinear and dynamic modulus-dependent models of asphalt mixture materials is described.Based on the non-linear viscoelastic assumption,the triaxial and bending-tension dynamic modulus-dependent models of asphalt mixtures are constructed,and the asphalt mixture under the same conditions is calculated Material triaxiality and dynamic modulus of bending and pulling.The results show that the nonlinear characteristics and dynamic modulus dependent models of asphalt mixture materials are equivalent.The dynamic modulus dependent models of asphalt mixtures can accurately characterize the temperature and load dependence of the dynamic modulus of asphalt mixtures.The material modulus provides a certain reference.Under the same conditions calculated by the model,the compression modulus is significantly greater than the flexural modulus,and the corresponding material parameters should be selected during structural design and mechanical analysis.