Multi-scale study of uniaxial compressive damage mechanical properties of asphalt mixture
Asphalt mixtures are multiphase inhomogeneous composite materials composed primarily of coarse aggregate,asphalt mortar,and voids.The internal structure of asphalt mixtures is irregular and the mechanical properties of the components are complex,which results in a highly complex process of accumulation and extension of fatigue damage.This paper predicts the fatigue mechanical parameters of asphalt mixtures on the basis of macro-mechanical tests using combined multi-scale algorithms and numerical simulations.It also investigates the mechanical attenuation of asphalt mixtures in the course of fatigue damage evolution employing combined micro-and macro-transversal scales.First,the relevant specifications are explored for building the mix ratio for asphalt mixtures with varying degrees of granularity.Then,uniaxial compression tests are performed on each group of specimens along with an unconfined compressive strength and fatigue test to observe and quantify the fatigue damage in relation to the evolution of the mechanical strength of different asphalt mixtures.Next,a statistical analysis is made on the digital images of the asphalt mixture specimen sections to determine the geometric morphology,spatial location,and other characteristic parameters of the aggregate particles.Based on the random polyhedral aggregates,a suitable mesoscale model is generated.The stiffness parameter of asphalt mixture AC-1.18 is employed as the initial iteration value for the computational procedure of the multiscale algorithm,which predicts the mechanical strengths of asphalt mixtures comprising different particle sizes through a process of progressive homogenization of the small-sized aggregate into a large-sized aggregate.We aim to predict the fatigue damage stiffness parameters of asphalt mixtures containing different grain sizes.A numerical model of a cylindrical mixture with polyhedral aggregates at different scales is generated by ABAQUS-Python based on the uniaxial compression test and the concept of a multiscale algorithm.Through multi-layer iteration,the compressive strength of the next level of asphalt mixture is predicted.Finally,we analyze the internal stress change and compressive strength attenuation law of the mixture during the fatigue damage evolution.The uniaxial compression test provides compressive strength parameters in the evolution of fatigue damage of the mixture as a macro test while the multiscale numerical simulation test yields a micro test result.Both the micro-scale and macro-scale tests are compared and analyzed.Our findings indicate the compressive strength of the asphalt mixture exhibits a gradual decline with an increase in the degree of fatigue and a subsequent rapid decline near the critical strength for failure.While there is a discrepancy(less than 9％)between the simulated compressive strength and the test results,our method meets the accuracy requirements and provides insights for enhancing the design and durability of asphalt mixtures.
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