| With the rapid development of economy and society,the traffic volume continues to increase,and the matrix asphalt pavement is prone to a large number of diseases in the actual use process,and the single modified asphalt road has defects in the comprehensive performance improvement of asphalt.Therefore,it is of practical significance to improve the comprehensive performance of asphalt pavement by composite modification,and the experimental study of polyester fiber-diatomite composite modified bitumen and its mixture is carried out.Firstly,the preparation of polyester fiber-diatomite composite modified bitumen was studied,and the performance tests of the three major indexes,viscosity,DSR,BBR and direct tensile of asphalt were carried out.Through experiments,it is found that when polyester fiber and diatomite are added to the matrix bitumen for composite modification,the penetration degree of the composite modified bitumen is reduced,the softening point is increased,the bonding performance is better,and the fracture performance is significantly improved.Through DSR test,it is found that the rutting factor of composite modified bitumen is significantly higher than that of matrix asphalt,and the dynamic shear resistance of composite modified bitumen is significantly larger.Secondly,the microscopic mechanism of composite modified bitumen was analyzed.By comparing the infrared spectra of matrix bitumen and composite modified bitumen,it is found that the modification method of polyester fiber-diatomite composite modified bitumen is physical modification.Fluorescence microscopy found that when the diatomaceous earth was mixed with 11%-13%,it was evenly dispersed inside the asphalt without agglomeration.SEM test observed that diatomaceous earth was adsorbed on polyester fibers and coated with bitumen,and an interwoven network structure was formed between polyester fibers to form a reinforcement effect,forming a stable structure inside the asphalt,which improved the high temperature,low temperature and water stability of matrix asphalt.Then,the response surface method is used to design the mixing ratio of composite modified asphalt mixture,determine the optimal content of polyester fiber and diatomaceous earth and the oil-stone ratio,and carry out road performance test.The rutting test showed that diatomite could improve the high temperature performance of asphalt mixture,the low temperature bending test showed that polyester fiber improved the low temperature performance of asphalt mixture,and the freeze-thaw splitting and water-immersion Marshall test showed that both diatomite and polyester fiber improved the water stability of asphalt mixture.Diatomaceous earth is adsorbed on polyester fiber,and polyester fiber forms an interwoven structure inside the asphalt,which acts on the asphalt mixture,so that the road performance of the asphalt mixture can be improved.Finally,the cracking behavior of composite modified asphalt mixture was studied by SCB test.Under the two conditions of considering displacement and not considering displacement,two types of SCB specimens,unopened and pre-opened,were tested,and from the perspectives of stress strength and fracture energy,it was found that the addition of polyester fiber could improve the cracking resistance of asphalt mixture,and with the strong adsorption of diatomite,the crack resistance of the mixture was optimal. |
