Analysis On Mechanical Behavior Of Asphalt Mixture With 3d Random Model

As a composite consist of asphalt and aggregates, asphalt mixture's mechanical property is closely related to the property of asphalt, aggregate's volume fraction, shape and gradation. In order to study and improve the mechanical property of asphalt mixture, it's necessary to establish a micromechanical model which can well simulate the aggregate's actual gradation, shape and distribution.By regarding asphalt mixture as a two-phase composite material consisting of asphalt sand and coarse aggregates, an algorithm of aggregate's creation and random packing is proposed. The three-dimensional random model can be generated by first packing randomly spherical aggregates created in accordance with an actual grading curve and then converting into polyhedron. The process of oscillation is employed to realize the movement of packed aggregate so as to avoid overlaps between aggregates.The constitutive relationship of asphalt sand can be described by the generalized Maxwell mode and the material model parameters are calculated by fitting the axial creep experiment data with nonlinear fitting method. The proposed model is validated by comparing the creep simulation and test results of asphalt mixture with a particular gradation. With the model,FEM numerical simulations are conducted to investigate the influence of aggregate distribution, content, shape and gradation on creep behavior of asphalt mixture. The result shows that the aggregate distribution doesn't greatly influence the mechanical behavior of asphalt mixture. The instantaneous elastic modulus increases with the increasing volume fraction of aggregate and ranges from Paul's bottom to top bound. Within the considered bound of aggregate size, the resisting ability of asphalt mixture increases with the increasing aggregate size and deviation factor of aggregate size. The resisting creep deformation ability of asphalt mixture decreases as the shape of aggregate becomes more slender. The result from numerical simulation of compress test indicates that the compress modulus of asphalt mixture increases with the increasing loading velocity.