Research On Self-healing Asphalt Material Based On Hollow Fiber Capillary

Bitumen is a widely used pavement material because of its low cost,corrosion resistance,temperature sensitivity and good adhesion.Under the influence of ultraviolet light irradiation,oxygen,temperature,humidity and evaporation,bitumen will be aging or even microcracks will be generated.It is hot issues for pavement of prolonging its service life,decreasing the maintenance cost,and improving the durability of roads.Nowadays,it has been found that the method of capillary hollow fiber containing rejuvenator is one of the effective methods to solve the aging of asphalt pavement and restore its original performanceIn this study,a dry-wet spinning technology was applied to successfully prepare hollow fiber in which oily rejuvenator agent is used as core material and polyvinylidene fluoride(PVDF)are designed as shell material.The property of stability,dispersion and penetration of hollow fiber in asphalt are investigated.The self-healing ability of hollow fiber for microcracks of aged asphalt was measured by mechanical method.First of all,the morphology,integrity,average size of PVDF hollow fiber,as well as the thickness of hollow fiber shell material,dense layer,finger pore and aggregation pore synthesis mechanism were studied.The investigation has shown that the pore structure of the hollow fiber shell is formed by the two-way diffusion of the solvent in the casting solution and the water in the coagulation bath.The results of microstructure confirmed that oily rejuvenator can penetrate the hollow fiber shell.The PVDF hollow fibers(30%)is the highest hydrophobicity and better compatibility in asphalt.The decomposition temperature of PVDF hollow fiber is about 450 ?,which is more stable in the integrity of the molten asphalt.Compared with the PVDF hollow fiber prepared by using water as the core liquid,the elongation at break of the PVDF hollow fiber with the oily rejuvenator as the core liquid is significantly reduced,and the elongation value decline from 341.2%(C1)to 23.4%(C2).From the water flux data,the minimum flux of 30%PVDF hollow fiber is 2.96 L/(m2 h).The PVDF hollow fiber containing the oily rejuvenator is formed into a composite material with the asphalt,and the tensile strength of the asphalt is compared by using a modified direct tensile tester to repeat the tensile test,thereby evaluating the self-repairing efficiency of the asphalt.The self-repairing efficiency of aged asphalt have an influence on the addition amount of PVDF hollow fiber containing oily rejuvenator,the degree of orientation of hollow fiber.Moreover,the asphalt sample tensile strength depends on temperature and time.All of the fibers in the asphalt matrix are parallel to the direction of stretching.The original tensile load is almost the same at about 122-115 N.After 24 h of the first self-healing process,the minimum tensile fracture value of the pure asphalt sample is 51 N;the other four fibers(containing 1-4 fibers)are sampled.The tensile load values are 65,66,73 and 74 N,respectively.After 24 h of the second healing process,the tensile load of the asphalt was 41 N,which was less than the value after the first healing.But the other samples had a tendency to decrease in elongation.The orientation of the fiber 0(15-75°)hardly affects the healing efficiency of the asphalt,and its value is about 72-75%,As the orientation 0 of the hollow fiber increases,the self-healing efficiency decreases remarkably.The final test temperature range is 0-30 ?,and elevated temperatures can significantly enhance the self-healing effect of each healing cycle.The above obtained results will provide basic research data for the self-healing of asphalt by the capillary hollow fiber method.