Study On Damage Characteristics And Meso Mechanism Of Asphalt Mixtures Reinforced With Basalt Fiber Under Freeze-Thaw Cycles

Due to the complex service environment and the increasing traffic load,there are more and more pavement siseases during the long-term service of asphalt pavement,resulting in a significant reduction in its service life,especially in the seasonal frozen areas such as northern China.Considering the severe climatic conditions,traffic load as well as freeze-thaw cycles,asphalt pavement damage would be occurred inevitablely and developed rapidly.Asphalt pavement damage not only severely affects its service performance and shortens service life,but also increases pavement maintenance costs,which will cause various inconveniences and social as well as economic losses.Therefore,it is necessary to improve the freeze-thaw resistance of asphalt mixtures,and the freeze-thaw damage mechanism of asphalt mixtures under freeze-thaw cycles needs to be clarified from the macro and meso perspectives.Meanwhile,the viscoelastic properties of asphalt mixtures containing basalt fibers could procide guidances for the evaluation and maintenance of asphalt pavement in actual engineering.This study was founded by National Natural Science Foundation of China“Research on damage model and mesoscopic characteristics of asphalt concrete under freeze-thaw cycle condition in seasonal frost area”.The asphalt mixture specimens reinforced by basalt fiber were firstly designed and prepared by Superpave gyratory compaction based on response surface methodology?RSM?.The analysis of freeze-thaw resistance of asphalt mixture reinforced by basalt fiber was also carried out.Then,based on the macro-mechanical properties,acoustic characteristics and mesoscopic characteristics,the freeze-thaw damage characteristics and reduction laws of asphalt mixtures were analyzed from macro perspective to meso-mechanism.Meanwhile,the static and dynamic viscoelastic mechanical responses of asphalt mixtures were discussed by using the static creep and dynamic modulus tests.The specific work carried out in this paper are as follows:1.The preparation parameters of basalt fiber-reinforced asphalt mixture were optimized based on response surface methodology and asphalt mixture specimens were prepared by Superpave gyratory compaction.According to the macro-mechanical performances of asphalt mixture specimens under freeze-thaw cycles,the effect of basalt fiber on asphalt mixture was evaluated in order to clarify the macro-mechanical reduction laws of asphalt mixtures.In addition,the acoustic emission technology was applied for analysing the internal damage of asphalt mixture to characterize the fracture characteristics of asphalt mixture specimens under freeze-thaw cycles.2.The X-ray computed tomography?CT?technology was used to obtain the microscopic images of basalt fiber reinforced asphalt mixture specimens under freeze-thaw cycles.Based on digital image processing?DIP?technology,the microscopic characteristic parameters of CT images were extracted to analyse the freeze-thaw damage of basalt fiber reinforced asphalt mixture.Then,the gray correlation analysis theory was adopted to explore the correlation degree between mesoscopic characteristic parameters and macro-mechanical properties of asphalt mixture and further clarify the freeze-thaw damage mechanism.3.Based on the basic viscoelastic theory,the static and dynamic viscoelastic mechanical responses of asphalt mixtures were studied by using the static creep and dynamic modulus tests,respectively.The Burgers model,generalized Maxwell model and generalized Kelvin model were used to characterize the creep and relaxation characteristics of asphalt mixture.The generalized Kelvin model and generalized Maxwell model could reflect the viscoelastic characteristics of asphalt mixture and describe its creep and relaxation behavior.Besides,the dynamic modulus,phase angle,storage modulus and loss modulus were used to analyse the dynamic viscoelastic mechanical response.The generalized Sigmoidal model was used to fit the main curves of storage modulus and loss modulus of asphalt mixture so that the elastic and viscous mechanical behavior of asphalt mixture could be studied in a wide time and temperature ranges.4.The uniaxial compression static creep test was used to analyze the static viscoelastic mechanical response of asphalt mixture reinforced by basalt fiber under freeze-thaw cycles.Then,the deformation resistance of asphalt mixture under freeze-thaw cycles was evaluated based on the parameters of viscoelastic model,i.e.,instantaneous elastic modulus?E₁?,instantaneous viscosity coefficient??₁?,delayed elastic modulus?E₂?and delayed viscosity coefficient??₂?of Burgers model.Meanwhile,the relaxation modulus of asphalt mixture reinforced by basalt fiber under freeze-thaw cycles could be also obtained based on the relationship between creep and relaxation in the Laplace domain.5.The dynamic modulus test was used to analyze the dynamic viscoelastic response of asphalt mixture reinforced by basalt fiber under freeze-thaw cycles.Based on the dynamic modulus and phase angle data of asphalt mixture,the storage modulus and loss modulus were further obtained in order to analyse the visco-elastoplastic behavior of asphalt mixture under freeze-thaw cycles.Then,the main curve of dynamic modulus was established to simulate the actual service conditions,and discussed the effects of traffic load and ambient temperature on mechanical properties of asphalt mixture,which could procide guidances for the evaluation and maintenance of asphalt pavement in actual engineering.