| Water damage is one of the most serious reasons of the early damage of the expressway asphalt mixture pavement in our Country. Among the reasons which can be controlled, the nature of the rock in the aggregate is the greatest impact on the water stability. Acidic aggregate such as gneiss, granite and gritstone can not be wildly used in road construction because of the poor adhesion to asphalt. Concerning the vast land and the great variety of geological structures in China, if some regions which are rich in acidic stone still keep pursuing the use of alkali, neutral stone, the project cost will be increased and the period of construction will be extended. Therefore, there is great significance in the study of water damage mechanism of acidic aggregate asphalt concrete and in the study of optimizing the design and preparation of acidic aggregate mixture.This thesis is based on the item "The optimization design and engineering application of the durable and multi-function asphalt pavement system on Wuying Expressway". The thesis is combined with the project, setting gneiss as a sample of acidic aggregate. Based on chemical reaction theory, surface energy theory and the theory of surface structure analysis, the author analyzed the internal factors of water damage. Based on the pavement structure behavior theory, the author analyzed the external factors of water damage and discussed the mechanism of water damage in gneiss asphalt concrete. On this basis, a optimize project of gneiss asphalt mixture has been proposed. By adding interface tackifier and cement and optimizing the design of the grading, a kind of gneiss asphalt mixture with good water stability and high temperature performance has been produced. Soaking residual stability is 92.8%,1 time freeze-thaw splitting intensity ratio is 93.9%,4 times freeze-thaw splitting intensity ratio is over 80.4%. The water stability is better than ordinary limestone asphalt mixture and dynamic stability is more than 5000times/mm. All the performances have met the requirements of high-grade rode use.According to the test results of chemical analysis and petrographic analysis and based on the analysis of surface energy theory, a kind of self-developed interface tackifier was added to improve the adhesion property between asphalt and aggregate whose adhesion rating became grade 5. After adding 6% of the tackifier into the asphalt, the softening point of the asphalt is 93℃, the viscosity of bitumen is as high as 85000Pa-s, so it can increase high temperature performance of mixture. According to theory of chemical reaction,2% of the cement anti-stripping agent was added. According to behavioral theory of pavement structure, by controlling the amount of fine aggregate, key sieve(0.075mm) and the asphalt film thickness, the key points of controlling the optimized design of gneiss asphalt mixture are proposed in order to optimize the grading design of gneiss asphalt mixture. The pass rate of the key sieve 2.36mm of AC-13:43%-49%, the pass rate of the key sieve 4.75 of AC-20: 46%-52%, the pass rate of the key sieve 4.75 of AC-25:46%-52%.The optimize project proposed in this thesis include adding interface tackifier and cement and optimizing the grading design, through which the problems that gneiss asphalt mixture shortage of water stability and durability have been effectively solved, and the project was successfully applied to Wuying expressway, which has great value of the economic promotion.
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