Fatigue Test Development And Evaluation Methodology Research Of Asphalt Mixture Based On Limited Thickness Specimen

Fatigue failure is one of the main damage forms of asphalt pavement.Existing fatigue tests of asphalt mixture could simulate the fatigue failure of asphalt pavement within a certain range,but it is hard to promote widespread utilizing owing to their cost restriction(expensive testing device,time-consuming specimen preparation and tedious operation).In addition,conventional fatigue tests could not evaluate the fatigue performance of the asphalt pavement after construction by using the core samples because of the limitation of the pavement thickness.In terms of such consideration,it is necessary to develop a new test method for fatigue performance evaluation of asphalt mixture with low-cost,time-saving and user-friendly operation.This research develops a new fatigue test method for asphalt mixture named as Disk Bending Fatigue Test based on the limited thickness specimen by a combination of computer numerical simulation and laboratory experiment.Then,a contrastive analysis between the Disk Bending Fatigue Test and Indirect Tensile Fatigue Test were conducted to verify the feasibility and reliability of the former.At last,the fatigue performance of four typical asphalt mixtures were evaluated by the new fatigue test method.Firstly,the finite element model of the Disk Bending Fatigue Test was created by employing the Abaqus software,then optimization by numerical simulation was conducted on the model.The proper size range of testing model and the suitable constraint form of mold were determined by comparing the mechanical response between the different loading fixture sizes,specimen thickness and constraint form of mold.Secondly,the Disk Bending Fatigue Test method was established by employed the Material Test System 810 and the self-design mold.Based on the laboratory experiment,the loading fixture with 12.5mm in radius,the disk testing specimen with 75 mm in radius and 30 mm in thickness were chosen as the testing dimension parameters.Then,the reliability of the testing method and the validity of the testing results were verified by parallel test and disparity processing.The method and steps of the Disk Bending Fatigue Test were given in the end.Thirdly,the fatigue comparison test under the same experimental parameters was conducted by employing the Indirect Tensile Fatigue Test.Fatigue deformation evolution rules,stiffness modulus attenuation curves under different loading frequencies and stress ratios,fatigue curves and fatigue damage curves between the two fatigue tests were employed through the contrastive analysis to prove the feasibility of the fatigue performance evaluation using disk bending fatigue test.Finally,the fatigue performance of four typical asphalt mixtures were evaluated based on the Disk Bending Fatigue Test.Fatigue performance were evaluated by the contrastive analysis of the deformation curves,fatigue curves and fatigue damage curves.Then,the reasons for difference in fatigue characteristic among the diverse asphalt mixtures were analyzed preliminarily.The Disk Bending Fatigue Test that has developed in this research focuses on the fatigue performance evaluation of the asphalt mixture with limited thickness,which is an effective method to make up the deficiency of the traditional fatigue tests,also provides technical support for the fatigue failure research of asphalt pavement.