| At present,the commonly used continuous dense-graded asphalt mixture design methods include Marshall method,GTM method and SUPERPAVE method.The design process is usually to first determine the mixture gradation,use different molding methods to form the specimen,and then determine the optimal amount of asphalt according to the volume index or mechanical index.The essence of these design methods is gradation priority.The purpose is to improve the anti-rutting performance of asphalt mixture and meet the requirements of volume index.For example,in the design of asphalt mixture in my country,the gradation of asphalt mixture is usually designed according to the engineering gradation range recommended by the specification,and the optimal amount of asphalt is determined according to the Marshall test.Once the gradation is determined,the optimal asphalt usage range is basically determined,and the performance of the designed asphalt mixture is determined.According to this process,the variation range of the optimal bitumen-aggregate ratio is very small.If the bitumen-aggregate ratio is slightly larger,high temperature diseases such as oil flooding and rutting will occur,and if the bitumen-aggregate ratio is slightly smaller,diseases such as looseness will occur.Although the asphalt mixture designed according to this design process is stable in quality,it is convenient for technical management.However,there is the problem of homogenization of asphalt mixtures,which makes it inconvenient to design functional pavement asphalt mixture materials with different performance and functional requirements.In this paper,the content of asphalt is determined first,and the content of filler is changed,based on the basic principle of volume filling.There are two approaches to provide functional pavement material design:(1)Asphalt-filler volume equivalent substitution method;(2)Determination of optimal filler dosage for asphalt priority.The functional pavement materials under the two design methods are verified by the road performance test of the mixture.The designed asphalt mixture has both excellently high temperature rutting resistance and low temperature cracking resistance,and excellently durability.The main conclusions are as follows:(1)The indoor test results show that the functional pavement materials designed by the asphalt-filler volumetric equivalent substitution method have excellent road performance at each asphalt mixtures.(2)The performance of the functional pavement material under the method of determining the optimal filler content with asphalt priority is better than that of the material designed by the traditional grading priority method.Compared with the optimal mix proportion of grading priority,the asphalt dosage and oil-stone ratio increased by 10%,the asphalt film thickness increased by 12%,and the filler dosage decreased by 26%.The rutting dynamic stability can reach 10864,and the maximum bending tensile strain in the trabecular bending test is more than 50% higher than that of the optimal mix ratio of graded priority.(3)The functional pavement material design method based on the idea of volume filling highlights the role of asphalt in mix design.The design idea of mix ratio of asphalt priority can improve the low temperature crack resistance of the mixture and improve the durability of the mixture while ensuring the high temperature stability of the mixture.The functional pavement material design method changes the traditional mix ratio design idea of first determining the gradation and then determining the amount of asphalt,which facilitates the design of functional pavement asphalt mixture materials with different performance and functional requirements.The asphalt mixture design method based on the priority determination of asphalt dosage facilitates the design of functional pavement materials with different properties and greatly improves their durability.Under the premise of ensuring the rutting resistance,asphalt dosage increase is conducive to asphalt mixture fatigue resistance,water damage resistance,anti-aging and other road performance of the overall improvement.The determination of asphalt dosage needs to be based on a combination of force characteristics of the layers,functional requirements and even experience and life cycle costs,which needs to be further studied. |
