Impact Of Polyester Fiber Diameter Shrinkage And Mechanics Performance Of Cement-stabilized Macadam

Shrinkage cracking of highway semi-rigid base course is one of the important reasons for many pavement diseases.Cement-stabilized macadam is the main semi-rigid base course material,and adding fiber is one of the main methods to improve the pavement performance of cement stabilized macadam.However,the current related achievements need to be further enriched and improved,so as to lays a foundation for improving the service life and quality of semi-rigid base course asphalt pavement structure.In this paper,based on the background of the construction status of high-grade cement stabilized macadam base in Jiangsu Province,physical experiments were carried out to obtain the best mixing process of fiber cement stabilized macadam mixture.on this basis,the influence of polyester fiber diameter change on the shrinkage and mechanical properties of cement stabilized macadam was studied,and its mechanism was analyzed.The basic law of the influence of fiber diameter change on the stress and road surface deformation of cement stabilized macadam base under vehicle load,temperature and their combined action is analyzed by ANSYS.the optimal diameter of polyester fiber was obtained and the method of determining the optimal diameter was put forward.Finally,the test road was verified and the application effect of the polyester fiber cement stabilized macadam(PETCSM)base layer was evaluated.Mainly achieved the following research results and conclusions:(1)Based on the method of judging the mixing effect of fiber cement stabilized macadam by combining macroscopic observation and performance stability evaluation of specimens,the suitable mixing process of fiber cement stabilized macadam mixture was put forward.(2)Under the same fiber quality and length,with the increase of fiber diameter,the PETCSM shrinkage coefficient decreased first and then increased(the fiber diameter appeared valley value at about 35?m),and the temperature shrinkage coefficient showed a linear growth trend,both the unconfined compressive strength and the splitting strength showed a linear decrease trend,the compressive resilience modulus basically unchanged.(3)For the PETCSM pavement structure,with the increase of the fiber diameter,the stress and road surface deformation of the foundation are all slightly fluctuating under the vehicle load,and there is no certain regularity;both under the temperature load alone and two combined loads have a gradually increasing trend,indicating that the temperature load plays a dominant role in the stress of the base layer relative to the vehicle load.(4)This paper proposes that the suitable fiber diameter of PETCSM is 20?m~35?m,the optimal fiber diameter is 20?m,and the method of determining the optimal fiber diameter which based on 7d temperature shrinkage coefficient and 28 d unconfined compressive strength as main control decision indicators while dry shrinkage coefficient as auxiliary decision indicators.(5)The addition of polyester fiber can reduce the magnitude of the strain change at the centerline and wheel trace of the two-wheeled track of the cement stabilized macadam base,indicating that the addition of fiber can effectively reduce the stress of the cement stabilized macadam base and improve its crack resistance.