Study On Fatigue Performance Of Composite Crumb Rubber Modified Asphalt Mixture Based On Macro-Meso Method

In recent years,with the increasing traffic volume,the asphalt pavement is overloaded,which causes premature fatigue damage and affects the performance of the pavement.Crumb rubber modified asphalt mixture is widely used in the cold areas of Inner Mongolia because of its good low temperature performance.It fully recycles waste rubber tires,which has significant economic benefits and environmental protection significance,but it also has some problems that need urgently.To solve the problem,when a single rubber powder is used to modify the asphalt,because it cannot comprehensively improve the performance of the pavement,the promotion and application of the crumb rubber modified asphalt mixture is restricted,making it a crumb rubber modified asphalt mixture.Obstacles to the development of materials.Therefore,this article considers compounding rubber powder modifiers and SBS modifiers to prepare composite crumb rubber modified asphalt mixture(CCRMA),and uses SBS modified asphalt mixture(SBSMA)as a comparative sample to study the aging And the effect of freeze-thaw cycles on the fatigue performance of composite crumb rubber modified asphalt mixture.First,based on the macroscopic scale,the semicircular bending fatigue test was performed on the composite crumb rubber modified asphalt mixture and SBS modified asphalt mixture before and after aging and freeze-thaw cycles.Evaluate its fatigue performance with indicators such as fatigue life,stiffness modulus,relative change rate of stiffness modulus attenuation(PV value)and other indicators;Based on the theory of damage mechanics,the damage factor D is defined by the relative change rate of stiffness modulus attenuation,the fatigue damage evolution law of asphalt mixture under different conditions is analyzed,and the fatigue damage model is established;the fatigue damage of asphalt mixture is established based on the phenomenological method Equations,and analyze the changes of the fatigue equation parameters under different conditions.The results show that the fatigue resistance of different asphalt mixtures decreases after aging and freeze-thaw cycles,and the composite crumb rubber modified asphalt mixture has better fatigue resistance than SBS modified asphalt mixture;recommended The PV value is used as the macro fatigue performance index to predict the fatigue life of the asphalt mixture and analyze the evolution of fatigue damage;the established fatigue damage model and fatigue equation have high fitting accuracy.Secondly,based on the meso-scale,the digital speckle correlation method(DSCM)was used to image the loading process of the semicircular bending fatigue test,and the displacement field,strain field and characteristic cloud image changes were obtained,and the main cracking areas were determined and studied.The effect of aging and freeze-thaw cycles on the deformation characteristics of the main cracking zone is analyzed;the horizontal tensile strain-time curve is used to analyze the change law of the horizontal tensile strain of the asphalt mixture during the fatigue loading process;the horizontal strain density(D_E)and based on the horizontal tensile strain are analyzed.Strain defines damage factors,and analyzes the effects of aging and freeze-thaw cycles on the fatigue performance and fatigue damage characteristics of asphalt mixtures.The results show that after aging and freeze-thaw cycles,the anti-fatigue damage ability of the asphalt mixture is reduced,and the damage rate increases,and the composite crumb rubber modified asphalt mixture has better fatigue resistance than the SBS modified asphalt mixture.Damage ability,that is,better fatigue resistance;compared with horizontal displacement,horizontal strain can accurately reflect the fatigue damage of asphalt mixture;The damage factor defined based on the horizontal tensile strain and the damage factor defined based on the relative change rate of the stiffness modulus attenuation are used to evaluate the fatigue damage characteristics of the asphalt mixture,and there is a consistent conclusion.Finally,through the correlation analysis of the fatigue life with the macro fatigue performance index PV value and the meso fatigue performance index D_Evalue,the results show that both the PV value and the D_Evalue can be used to effectively evaluate the fatigue performance of the asphalt mixture;The correlation analysis between the value and the D_Evalue shows that the application of the DSCM method to the semicircular bending fatigue test to study the influence of aging and freeze-thaw cycle conditions on the fatigue performance of asphalt mixtures has a certain degree of reliability.