The Research On Application Of Polyacrylonitrile Fiber In The Asphalt Mixture Pavement

To improve road performance of asphalt mixture pavement, it is very important means that new materials, new equipments and new technology are used to reduce damages of asphalt pavement and prolong its life in the process of reforming backward technique of asphalt pavement. Polyacrylonitrile fiber as a new type of adding material has the characteristics of high strength, high absorption, chemical property stable and good dispersion. It can improve significantly high temperature resisting deformation and low temperature anti-cracking property to prolong the life of pavement. So polyacrylonitrile fiber has a good application prospect.This paper systemically studied the application of polyacrylonitrile fiber in asphalt mixture, the main content as follows:First, the morphology of polyacrylonitrile fiber was analyzed:the length and the thickness are relatively uniform, length about6mm, diameter about18μm. Its cross-section is approximated to be circular. The fiber along its length has rough and clear texture. The two ends of fiber have noticeable projections. Secondly, by oil absorbency test, water absorbency test and high temperature test, the suitability of the fiber and asphalt mixtures was analyzed. The results show that fibers have good oil absorbency and lower water absorbency. At220℃high temperature, the morphology, chemical composition and strength of polyacrylonitrile fiber remain hardly unchanged. This shows that the suitability between the fiber and asphalt mixtures is very good.Second, the influence of polyacrylonitrile fiber on performance of asphalt mortar was studied by cone penetration test, bending beam rheological test and dynamic shear rheological test. To start with, temperature sensitivity of asphalt mortar is reduced by adding fibers effectively. And fibers can play tackifying and thickening active roles in asphalt mortar. Simultaneously, the shear strength of asphalt mortar is increased clearly. So high temperature performance of asphalt mortar is improved effectively. At low temperatures, the strength and the resisting transformation of polyacrylonitrile fiber asphalt mortar are reinforced apparently. But the malleability of fiber asphalt mortar is reduced slightly. There are good relativity between rheological parameter G*、δ、G’、G"、G*/sinδ and the temperature. And the ratio of renewable elastic part of fiber asphalt mortar is increased by adding fibers. And rutting resistance factor G*/sin5of fiber asphalt mortar is raised clearly, this shows that rutting resistance performance at high temperature is improved obviously. By SEM and FTIR, it is discovered that fibers are randomly distributed throughout asphalt mortar, and physical absorption or binding happens in the interfaces between fibers and asphalt, and the chemical species of asphalt remain unchanged.Third, by three rutting tests of TRLL, CPN and AAPA, it is discovered that polyacrylonitrile fibers may improve rutting resistance performance of asphalt mixture at high temperature apparently. Polyacrylonitrile fibers distribute randomly in asphalt mixture by way of "bridging" and "the lap" and play tackifying, stabilizing and reinforcing roles.Tthere are good relativity between TRLL and AAPA. it is discovered that by beam bending test at low temperature anti-cracking performance of fiber asphalt mixture may be improved clearly because of the roles of crack resistance and stress dispersion of fibers. It is discovered that by immersion Marshall Test the performance of resisting damage of water of fiber asphalt mixture may be improved significantly because of the roles of tackifying and reducing void ratio of fibers. And the optimum containing of polyacrylonitrile fiber in asphalt mixture is0.3%.Fourth, viscoelasticities of polyacrylonitrile fiber asphalt mastic and polyacrylonitrile fiber asphalt mixture were studied using the Burgers model, and the fitting parameters of the Burgers model of fiber asphalt mastic and fiber asphalt mixture were obtained. Tests show that the Burgers model is valid to describe the mechanics behavior of viscoelasticities of fiber asphalt mastic and fiber asphalt mixture.Finally, application in test roads has received prominent effects. And the construction requirements of polyacrylonitrile fiber asphalt pavement are obtained. With the construction of normal asphalt pavement, dry mixing time of fiber asphalt mixture must extend10seconds to15seconds, and the construction temperature of fiber asphalt pavement must be increased by10degrees to15degrees.