Study On The Fatigue Performance Of Chopped Fiber Asphalt Mixture

In the development of asphalt pavement,fiber has been known as pavement reinforcement material to many researchers and designers.The incorporation of fibers can improve the low-temperature and high-temperature performance of the asphalt mixture,increase the ability to absorb asphalt,and extend the service life of the pavement.Through the test comparative analysis method,combined with the characteristics of asphalt mixture,studied the pavement performance improvement of a variety of chopped fiber,and summed up the fiber engineering environmental applicability.This article mainly focuses on the characteristics that the asphalt mixture is a typical viscoelastic material and the viscoelastic properties of the material will affect its performance.In order to analyze the effect of fiber on the viscoelasticity of asphalt mixture and the effect of viscoelasticity on the pavement performance,a large number of experiments were conducted by dynamic mechanical analysis(DMA)combined with asphalt mixture performance tests.The six kinds of asphalt mixtures were design in the most compact state to obtain the best ratio of oil to stone by Multi-performance design of hot mix asphalt based on stone interlock structure theory.Then they were subjected to frequency sweeping and repeated bending tests with dynamic mechanical analysis(DMA)to obtain their viscoelastic parameters and fatigue life.At the same time,the six kinds of asphalt mixtures were subjected to routine road performance tests in the laboratory to obtain high-temperature,low-temperature and fatigue performance.The DMA frequency scanning results were used to analyze the factors affecting the viscoelastic parameters of the fiber asphalt mixture.At the same time,the main curves of the dynamic modulus were made with two different conversion methods,and based on these multiple modulus indicators were obtained.The modulus index combined with the test results of road performance were used to evaluate the high and low temperature performance of the asphalt mixture and to understand the high and low temperature performance improved by various types of fiber.And verify the reliability of the modulus index.The durability performance of several asphalt mixtures was evaluated using the same fatigue criticality criteria as the asphalt mixture DAM fatigue test and the four-point bending fatigue test,and the fatigue life obtained by the two test methods was compared to verify the feasibility of the asphalt mixture DMA fatigue test.At the same time,the strain level equation for the fatigue life of the DMA fatigue test was established.Based on the discussion of fatigue criticality criteria,a fatigue life prediction method is proposed,and a functional relationship between DMA estimated fatigue life and measured fatigue life is established.Finally,the structural characteristics of DMA fatigue specimens were analyzed by digital image processing method.The influence factors of mechanical durability were analyzed from the angles of material type,structure,and initial viscoelastic parameters by the method of gray correlation degree calculation.The experimental research shows that DMA method has certain reliability in the research of asphalt mixture performance.The viscoelastic parameters of asphalt mixture have a close relationship with its pavement performance.Although the improvement in the road performance of fibers is present,not all fibers can improve all of the pavement performance.Therefore,the use of fiber reinforced materials in engineering should be carefully selected in conjunction with the engineering environment.