| The quality of mineral aggregate which accounted for95%of the total mass. The early damage of asphalt pavement has an important relationship with aggregate gradation. High temperature performance and resistance to water damage requires special performance for ChongQing asphalt pavement especially in summerand autumn with hot and rainy. For the reasons of significantly improve the high temperature stability of asphalt pavement and durability of resistance to waterdamage, the paper has specialized research on the aggregate grading of asphaltpavement.The research results showed that mineral aggregate gradation had an important impact on forepart breakage of highway asphalt pavement. It is hot and rainyin summer with a long time in Chongqing; besides Most of the areas are characterized with having high mountains. Therefore, harsh conditions in Chongqing areas set forth stricter requirements for the road performance of asphalt mixtures and in order to improve significantly road performance and durability, it is necessary to carry out specialized research on aggregate gradation.Firstly, the suited aggregate was found through looking up research results and current situations of aggregate grading at home and abroad and then surveying typical aggregate plants. Secondly, an optimized proportion of asphalt mixtureswhich include three surfaces of different structures AC-20、AC-16and SMA-13used commonly in Chongqing expressways is designed according to the current situation of expressway construction in Chongqing area. Besides, fractal theory and design approach are selected as the reference method of experiment researchesand designing schemes as well as coarse aggregate with different fractal dimension and proportion is chosen to carry out the bulk density experiment for looking for the gradation range of it with little interval rate; continuous grading is optioned based on previous studies on fine aggregate; preference is given to part ofcurves to carry out follow-on experiment according to proposing many gradingcurves to conduct the preliminary test and comparing with relative volume indexes of aggregate in every grading curve. Finally, test specimens are made by compaction method based on certain grading curves and performance indexes of asphalt mixture such as volume, high temperature and resisting the water damage aretested and concluded according to the optimal asphalt content. The research results are shown in the following: the calculation method of fractal theory has correlated well with asphalt mixture gradation; however, it needs to adjust the passing rate value of some screen holes. In the process of fractalgraduation, the minimum point of AC-20clearance rate is in the vicinity of D=2.5; when D equals2.4, AC-16get the maximum clearance rate and when D equals2.5as well as2.6, the skeleton structure of fractal gradation is tending towards stability; when D lies between2.55and2.65, SMA-13gets the minimum clearance rate. With the increase of fractal dimension, the elevated temperature property of asphalt mixture increases first and then decreases as well as the water-resisting property increases gradually. The grading range of dense asphalt mixture AC-20and AC-16fit for Chongqing areas lies corresponding interval of D=2.40~2.55; The grading range of SMA-13lies corresponding interval of D=2.55~2.70.The purpose of this thesis is to improve anti-rutting performance and water-resisting property of asphalt pavement; what is more, it puts forward the recommending range of aggregate gradation used in asphalt pavement of ChongQing area. |
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