Study On Double-layer Porous Asphalt Mixture Optimize Design And Pavement Performance

With the continuous development of traffic technology,people have higher and higher requirements for road safety and comfort,and porous asphalt pavement with good driving safety and comfort is more and more used in new construction or maintenance projects.Compared with single-layer porous asphalt pavement,doublelayer porous asphalt pavement has better function of resisting sliding,preventing blockage,reducing water mist and reducing noise.In China,the research and application of porous asphalt pavement started rather late,and there are few researches on double-layer porous asphalt pavement.Based on the scientific research project of the experimental road in Guangji expressway,this paper conducts further research on gradation and material optimization of double-layer porous asphalt pavement.Firstly,the paper focused on the research of asphalt binder for double-layer porous asphalt pavement.Through the performance test of asphalt binder,this paper compared the different modifier types and dosage of modifier,and the matrix asphalt and rubber asphalt distribution effect.The results show that different high viscosity modifiers have different viscosity-increasing effects,and the rubber asphalt with 8% high viscosity modifier content has good high temperature performance,low temperature performance and water stability.Secondly,the gradation design was studied in this paper,orthogonal tests were designed to explore the relationship between the gradation and the air void of PAC-10 and PAC-16 asphalt mixture,and linear regression fitting models were established for passing ratio of key sieve and air void of the mixtures.The test shows that the linear model has better accuracy,and the correlation between the passing ratio of 2.36 mm sieve and the air void is the best.According to the target air voids of the upper and lower layers,the gradation is calculated by the linear models.Compared with the median limit gradation given in the two specifications of the Ministry of Communications and the Ministry of Housing and Urban-Rural Development,the gradation of PAC-10 is very different and the gradatin of PAC-16 is relatively close.Thirdly,the pavement performance of the mixture was tested in this paper,the pavement performance of different gradation,different modifier content and different types of asphalt binders were compared.The test results show that the asphalt mixture with the gradation of this paper has good pavement performance.The fine aggregate content of PAC-10 is less in the Ministry of Housing and Urban-Rural Development,the fine gradation of PAC-10 is higher in the Ministry of Housing and Urban-Rural Development and the passing ratio of 4.75 mm sieve is too high,which reduce the pavement performance of the mixture.The pavement performance of the asphalt mixture can be improved by increasing the content of the high viscosity modifier.Compared with the high viscosity modified matrix asphalt,the high viscosity modified rubber asphalt has better low temperature performance and water stability.Fourthly,the performance and fracture of limestone were studied.Although the aggregate performance of limestone is far worse than basalt,it was found that the pavement performance of limestone asphalt mixture is only slightly lower than that of basalt asphalt mixture through the the mixture test,and the pavement performance can also meet standard requriement.The limestone is easy to be broken in the process of compaction,and all the coarse aggregate are involved in the crushing,and the proportion of aggregate crushing is close.The experimental study shows that,if the drainage performance of limestone asphalt mixture is more important,the compaction times,compaction temperature and other conditions should be controlled lower than that of basalt asphalt mixture.If the mechanical performance of limestone asphalt mixture is more important,we should take the same construction technology as basalt asphalt mixture.Finally,based on the scientific research project of the experimental road in Guangji expressway,the mechanical response,fatigue life and permanent deformation of double-layer porous asphalt pavement with different thickness were analyzed with finite element software.Combined with the drainage performance and mechanical performance,the recommended asphalt content between two layers is given,and the contruction requirements for porous pavement are put forward.