Composition Mechanism Of Asphalt Mixtures

The major structure style of Chinese high-type highway at present is asphalt pavement, thus the asphalt mixture performance directly influence the serviceability and service life of highway. Modern heavy-duty traffic requires that asphalt mixture has good high-temperature stability and other performances. In order to improve and optimize the asphalt mixture performance, a large number of new materials and theories appear recently. But existing study can not deeply reveal the structure mechanism of asphalt mixture, because their major study objects are macroscopical performance of the asphalt mixture and experience indexs are always used as key index for evaluate its performance..All of the above make the mixture desigh theory lose essential theory fundament.In order to deeply understand the relation between composition and macroscopical performance of asphalt mixture and provide necessary theory guide for its mix design, this paper thoroughly study the composition mechanism of the asphalt mixture. This paper includes the study of gradation composition, mixture design method and micro-structure parameter of the asphalt mixture. This paper firstly studies two basic gradation conditions -dense structure and framework structure, and then analyse the influence of different particle structure on the gradation. This paper indicate that the contact point between particles is the major load-carrying element of the framework structure and establish gradation computing model in which coarse aggregate has several support points and framework condition. This model has largest carrying capacity. Using this computing model and importing mixture volumetric parameter which includes VCA,VMA and VV,the volumetric mix design method based on multi-supporting framework condition is established.. This design method achieves the objectivity of design process and unification of gradation design and asphalt mixture design. Verified by the experiments, the mixture designed by this method exhibit good high-temperature stability .Through practical experiments, this paper correct the aggregate surface-area coefficient which is used to calculate asphalt membrane thickness in exiting specification. Using the sample vacuum density instrument developed by ourselves, the asphalt mixture void structure is tested, new void classification and its testing method is advanced and the relation between void structure and mixture macroscopical performance is studied.This paper uncovers the composition characteristic and structure mechanism of the asphalt mixture in micro-level, provides new mix design method of asphalt mixture, explores the micro-analysis means of asphalt mixture and establishes some theory basis for further study of asphalt mixture.