Mesoscopical Study On Uniaxial Compression Test Of Asphalt Mixtures Based On Aggregate Characteristics

Asphalt mixture is not a homogeneous material on conventional assumptions,as a multiphase material,whose mechanical properties are determined by nature and characteristics of each components(aggregates,asphalt sands and voids,etc.).It is an important problem to be solved in asphalt pavement design,how to quantitatively analyze the difference of individual morphological characteristics of aggregate and the interaction mechanism in asphalt mixture.Research on mesomechanics has been of considerable interest,represented by digital image technology(DIT)and the discrete element method(DEM),which provides an effective way to understand the internal structure and performance of asphalt mixture.Based on aggregate shape and distribution laws,study on accumulation behavior and filling characteristics of single particle size and double particle size were carried out by aggregate packing model in PFC3D software.Meanwhile,applicability and rationality of key size in Bailey method were verified combining interference theory.Two methods,the static compacting method and the Marshall compacting method,are simulated and analyzed with parameters such as porosity and coordination number,by which internal components change laws of four random asphalt mixture specimens were evaluated quantitatively.The numerical simulation results were validated by the laboratory CT test.Projection plane and long and short axis length of real aggregate were analyzed using DIT and probabilistic method.In addition,an irregular aggregate random generation algorithm was proposed upon aggregate characteristics.Asphalt mixture multiscale model was established by assigning different contact states to aggregate and mortar components.The contact microscopic parameters were converted by the macroscopic properties of aggregate and mortar,and were calibrated using laboratory uniaxial tests.In the end,the influence of aggregate properties change on mechanical properties of asphalt mixture was further studied.The results showed that the accumulation effect of aggregate is closely related to particle size and boundary effect,and the key particle size of Bailey method is equally applicable under three-dimensional conditions;the Marshall compaction makes the specimen more compact and reaching a relatively stable state in a short time,and the uniformity of the aggregate distribution is affected by its particle size;the Gaussian distribution model has a good correlation with the measurement results of aggregate shape parameters;the microstructure and mechanical properties of the real specimen may be well characterized and described by the uniaxial virtual specimen of asphalt mixture established with irregular aggregates,but accurate analysis of the impact of aggregate properties on asphalt mixture performance is still technically difficult.Aggregate morphological characteristics and micromechanical mechanism are both preliminarily discussed,and a virtual modeling method for asphalt mixtures was developed.So the research results can provide a reference and basis for the further research on microscopic study,and it has a certain economic and practical value by reducing repeated test costs and dependency on test equipment.