Research On Key Parameters And Viscoelastic Analysis Of Asphalt Mixture Based On Semi-circular Bending Strength Test At Low And Moderate Temperature

The crack resistance of asphalt mixture is very important for the development and prevention of pavement.However,the effect of the key parameters for semicircle bending test,such as temperature,loading rate and specimen thickness,are not clear.Also,the fracture critical criterion does not apply for the viscoelastic analysis,which limits the further development of semicircle bending test to evaluate crack resistance.Therefore,to research the key parameters of the semi-circular bending strength test of asphalt mixture at medium and low temperature as while as the viscoelastic analysis of the fracture process is urgently.First of all,the semicircle bending fracture test of AC-13 and SMA-13 were carried out with 5kinds of specimen thickness,7 kinds of temperature and 12 kinds of loading rate,analyzing the change rule of five indexes with different combinations of test parameters,and establishing the main curve equation of each index with loading rate.Secondly,based on the analysis of each index of load-displacement curve of semicircle bending fracture test,through the analytic hierarchy process(AHP),comprehensive cracking resistance indexes were proposed: fracture resistance index(FRI)and cracking resistance index(CRI).The effectiveness of the index was verified from two aspects of variability and discrimination as well as the best loading rate under different temperatures was determined.Next,the dynamic modulus test method of semicircle bending was conducted,and the main curves and phase angles of dynamic modulus and storage modulus of AC-13 and SMA-13 gradations were obtained.The difference and internal mechanism between SMA-13 and AC-13 gradations were analyzed.The viscoelastic parameters of Burgers model of AC-13 and SMA-13 gradations were fitted by numerical fitting and analytical limit method.Finally,based on the semicircle bending fracture test and Burgers model parameters,the viscoelastic fracture criterion maximum energy release rate of asphalt mixture was calculated,and the main curve of maximum energy release rate of SMA-13 and AC-13 grading was obtained.Based on the comparison results,the effectiveness of the index as the extreme viscoelastic parameter was analyzed,and the critical fracture characteristics of SMA-13 asphalt mixture with loading rate were clarified.In order to improve the theoretical framework of viscoelastic analysis of semicircle bending fracture test,the strong correlation between the maximum energy release rate and each index of load-displacement curve was analyzed.In this study,the key parameters of semicircle bending fracture test were determined,the comprehensive evaluation indexes CRI and FRI were proposed,the maximum energy release rate of viscoelastic limit state was calculated,and the theoretical framework of viscoelastic fracture analysis under semicircle bending stress mode was improved,so as to promote the development of semicircle bending test in the evaluation of crack resistance.