Freeze-thaw Splitting Test And Numerical Simulation Of Fiber Asphalt Mixture

The composition of fiber asphalt mixture is so complex that its complexity leads the mechanical properties of the fiber asphalt mixture to be also correspondingly complex.This paper studies the fiber types,content and the number of parameters for freezing and thawing,starting from the splitting test of fiber asphalt concrete,to evaluate the freeze-thaw performance of fiber reinforced asphalt concrete.Through a large number of laboratory tests and theoretical analysis,the water stability of asphalt mixture adding polyester fiber,basalt fiber,lignin fiber whose content is 0.3%,0.35%,0.4%,0.45%under the action of clear water is studied in detail,which can provide reference for the influence of fiber type and amount of asphalt mixture on asphalt mixture.This paper also established a three-dimensional asphalt mixture splitting finite element model,by contrasting the relationship between the numerical simulation results and experimental results,which verify the rationality of the fiber asphalt mixture Marshall specimen of finite element model;In view of the distribution of stress and strain nephogram obtained by numerical simulation of splitting model of Marshall asphalt mixture,the mechanical characteristics of asphalt mixture specimen are analyzed.The experimental results and numerical simulation results show that:(1)With the increase of the number of freeze-thaw,the splitting strength of asphalt concrete specimens with fiber is reduced;the main reason is that the water in the specimen undergoes constant freezing and thawing during the freezing and thawing cycles,which led directly to undermine the internal structure.(2)With the increase of fiber content,the basic trend of the splitting strength of unfrozen specimens is the same,almost all rising first and then decreasing.When the number of freeze-thaw cycles is 2,4,6,the splitting strength of specimens is similar to that of non freezing.Mainly because of high fiber content will be generated when the cluster phenomenon,resulting in uneven mixing of fiber and asphalt as well as aggregate,splitting strength will decrease.When the number of freezing and thawing is same,whether it is 2,4 or 6,the specimens with the smallest freeze-thaw strength are the specimens with the smallest amount of fiber.In the fiber content under the same conditions,whether it is 0.3%,0.35%,0.4%or 0.45%,specimen's splitting strength is the smallest which has the highest number of freeze-thaw.(3)Asphalt concrete splitting strength will have the best value after 6 freeze-thaw cycles including fiber content of 0.3%,0.35%,0.4%,0.45%.In this paper,the optimum content of fiber is 0.4%and the best fiber is basalt fiber.Under the above two data conditions,the fiber reinforced effect is the best and the specimen has the best freeze-thaw performance at this time.(4)The experimental data of ultrasonic wave and the fiber asphalt mixture Marshall test results of strength detection show that the exponential function fitting ultrasonic velocity and asphalt mixture after freeze-thaw cycles of splitting strength can correctly reflect the attenuation performance of asphalt mixture in the process of freezing and thawing.For the specimen mixed with polyester fiber,the fitting formula of wave velocity and strength is f = 4.42477×10-7e0.0031v,R~2 = 0.89431;for specimens with basalt fiber,the fitting formula of wave velocity and strength is f = 1.25069×10-8e0.00467v,R~2 =0.86403;for specimens incorporating lignin fibers,the fitting formula of wave velocity and strength is f = 5.05944×10-11e0.00487v,R~2 = 0.96903 When researching the freeze-thaw damage of asphalt mixture by ultrasonic method and using the change of wave velocity to reflect the degree of freeze-thaw damage,the degree of damage after freezing and thawing is related to the number of freeze-thaw cycles.(5)Through face-to-face contact loading simulation of mixed material splitting test,this paper establishes a three-dimensional fiber Marshall specimen ANSYS analysis model;based on the results of freeze-thaw splitting test and ultrasonic test,a three-dimensional finite element model of fiber reinforced asphalt concrete is established;through the comparison and analysis between the numerical simulation and the measured results,the rationality of the finite element model of the fiber reinforced asphalt concrete Marshall test specimen is verified,and the corresponding rules are obtained...