Investigation Of The Effect Of Basalt Fiber On The Performance Of SMA-13 Hot Recycled Asphalt Mixture

As a high-value utilization method of reclaimed asphalt pavement(RAP),hot recycling technologies are gradually widely used.hot recycling technologiesmainly inclue in plant hot recycling and in situ hot recycling.as for the hot recycling of SMA asphalt pavement,these two technologiesface some problems.Firstly,the perforamce of recycled aspgalt mixtures,for both of the in plant hot recycling and in situ hot recycling,degraded to a great extent,especially for the low-temperature cracking resistance.Secondly,the lignin fiber used in SMA asphalt mixture would gradually fail during the aging process,and new fibers used as stabilizer are essential during the recycling process.Basalt fibers have been proved to improve the comprehensive performance of asphalt mixtures.Therefore,this thesis intends to inreoduce basalt fiber into the hot recycling of SMA asphalt mixtures,so as to stablize the asphaltbinders,and improve the performance of the mixtures as well.Firstly,the aging degree of the extracted old asphalt in the RAP was evaluated,and the dosage of the regenerating agent was determined.The recycled old asphalt was obtained from the RAP by extraction,centrifugation,and rotary evaporation.The properties of the old asphalt were tested,and the aging degree was determined to be grade Ⅱ mildly aged.The regenerating agent with the type of RA102 was selected to fabricated the recycled asphalt.The proper dosage of the regenerating agent was 6%by the weight of the binder,based on the of the property recovery of penetration,ductility and softening point.The high and low temperature rheology properties were conducted by dynamic shear rheology and bending beam rheology tests.The viscosity-temperature curve was also investigated by rotational viscosity test.The results show that the regenerating agent can improve the low temperature rheology properties effectively,and reduce the mixing and compaction temperature.However,the high temperature properties will be negatively impacted.Secondly,the mixtue design of SMA-13 hot recycled asphalt mixtures were conducted by Marshall test design method.Basalt fibers were selected as the new fiber,and lignin fiber were also used for comparision.Then,asphalt mixtures with the RAP content of 0%,30%,and 80%,which represent the hot-mix SMA-13,in Plant hot recycling SMA-13,and in-situ hot recycling SMA-13,respectively,were designed.As for the in-situ hot recycling mixtures,the fibers were firstly added into the 20%of new mixted mixtures,and then mixed with 80%RAP.As for the in Plant hot recycling mixtures,the fibers were firstly dry-mixed with the aggregate,and then mixed with RAP,new asphalt,and mineral fillers.In addition,the dispersibility of basalt fibers in the in-situ hot recycling mixtures was detected by the centrifugation-extraction method.the results indicate that the of basalt fiber were uniformly dispersed in the hot recycling mixtures.Thirdly,the effect of basalt fibers on the road performance of SMA-13 hot recycled asphalt mixture were investigated by laboratory experiments.The results of wheel tracking,uniaxial penetration,and low-temperature bending beam tests show that basalt fibers are beneficial to the high-temperature performance of the recycled asphalt mixtures,and significantly improves the low-temperature performance.The results of immersion Marshall test and freeze-thaw splitting testpresent that basalt fibers have no significant effect on the water stability of the recycled asphalt mixture.However,the results of Hamburg wheel tracking test show that the basalt fibers can effectively decelerate the creep rate and flaking rate of the recycled mixtures,indicating that the basalt fiber can effectively enhance the high-temperature deformation resistance and the spalling resistance when exposed to moisture and hot envirommental conditions.Finally,the cracking resistance and viscoelasticity of SMA-13 hot recycled asphalt mixture were studied through semicircular bending tensile test,dynamic modulus test,low temperature bending creep test,and dynamic creep test.The results show that compared with conventional SMA-13 hot recycled asphalt mixture with lignin fibers,basalt fibers can enhance its fracture energy and delay the propagation rate of the cracks,for both in-situ hot recycling and in plant hot recycling asphalt mixture.It indicates that basalt fibers can greatly improve the crack resistance of recycled asphalt mixture.in addition,at higher temperatures,basalt fibers can significantly reduce the creep rate of recycled asphalt mixture,prevent the flow and deformation of the asphalt,so as to improve the high temperature stability.at lower temperatures,basalt fiber can greatly increase the ratio of dissipated energy of recycled asphalt mixtures.It indicates that basalt fibers can quickly dissipate the accumulated stress,thereby improving the stress relaxation ability of recycled asphalt mixtures.In brief,using basalt fiber instead of lignin fiber in the hot recycling of SMA-13 can significantly improve the high temperature performance,low temperature performance,water stability and anti-cracking performance of mixtures.These results can provide useful reference and guidance for the utilization of basalt fiber in the hot recycling of SMA-13 asphalt mixtures.