Research On Performances Of Hybrid Fiber Modified Asphalt Mixtures

At present China is being in a period of road traffic growing with a high speed, so pavement materials with high quality are indispensible to develop. Fiber modified asphalt mixture can meet demand of road traffic to a certain extent because of its good performances. Nevertheless different sorts of fiber have great disparity on function and quotation because of the production of fiber is still not very canonical, which has became a key problem restricting the progress of fiber modified asphalt concrete. In this paper a kind of asphalt mixture containing hybrid fiber is prepared and investigated. The Hybrid Fiber used in this paper is constitutive of cellulose fiber and polyester fiber which are two kinds of most wildly used fibers at present. Many experiments from mini scale to macroscopy are carried out about hybrid fiber modified asphalt mortar, sand asphalt mixture and asphalt mixtures.Firstly the influences of hybrid fiber on the performance of asphalt mortar were researched adopting binder drainage test, awl penetration test and dynamic shear rheometer (DSR) test. The results show that polyester fiber can increase tendon and viscosity better, while cellulose fiber can stability the unrestricted asphalt better. Hybrid fiber which contains 20% ~ 50% cellulose fiber can improve the resistance to shearing and rutting. The results also show that there still have many shortages for DSR test to evaluate the propertied of fiber modified asphalt mortar.Then based on the researches of asphalt mortar, experimentations about sand asphalt mixture were carried out. And uniaxial compression test, creep test and direct shear test were designed and rheological properties were investigated. Analyzed the influences of hybrid fiber on the resistance of sand asphalt mixture to lower-temperature cracking and high-temperature deformation, which validated the hybrid fiber containing 40% cellulose fiber has better performance.At last hybrid fiber modified asphalt mixture was prepared. The influences of hybrid fiber compositive proportion to optimum asphalt ratio, volume of voids and Marshall Stability were researched. Adopting prolonged rutting test the higher-temperature deformation resistance of asphalt mixture was evaluated; adopting bending test the lower-temperature cracking resistance of asphalt mixture was evaluated; water damage resistance property was evaluated adopting Marshall Water Submerged Stability test and Freeze-Thaw Split test; and indirect tension fatigue tests were also carried out.A comprehensive analysis to performances of hybrid fiber modified asphalt mixture was performed and the results show that asphalt mixture has better performances when the proportion of cellulose fiber in hybrid fiber ranges from 20% to 50% and 40% would be the best value. Taking the proportion of 40% for example, hybrid fiber can decrease the cost of fiber modified asphalt mixture markedly.