Research On Performance Decay Characteristic And Mechanism Of Basalt Fiber-Modified Asphalt Mixture Under Freeze-thaw Cycles

Under the coupling of water and low temperature,the asphalt concrete pavement will be damaged seriously by freeze-thaw cycles,and the damage of the pavement in a seasonally frozen ground region is more obvious.Adding fiber is a common method to improve the freeze-thaw damage resistance of asphalt concrete.Basalt fiber is a mineral fiber that gradually begins to be applied.It can play the role of reinforcement,dispersio n,adsorption,stabilization and viscosity enhancement,and can significantly improve the pavement performance of asphalt mixture.In recent years,the research on the production of basalt fiber has been gradually carried out in China,and the technical specifications of the corresponding basalt fiber asphalt mixture have been formulated,which promotes the application of basalt fiber asphalt mixture in road engineering.However,due to the harsh climatic conditions in the seasonal frozen zone and the unclear damage law and mechanism of the mechanical properties of basalt fiber asphalt mixture under the freeze-thaw cycles,the popularization of basalt fiber asphalt mixture in seasonal frozen area is hindered.Although the research on macro-performance of asphalt concrete freeze-thaw damage has been carried out for a long time,the research is still not comprehensive enough,the understanding of crack propagation in freeze-thaw cycles is not deep enough,the damage process and mechanism of asphalt concrete are not clear at the meso-level,and the influence of complex mechanical properties such as viscoelasticity and fatigue performance is also less studied.Therefore,it is necessary to further study the effect of freeze-thaw cycles on the performance of asphalt mixtures.Combining with the project of National Natural Fund of China "Research on damage model and meso-characteristics of asphalt concrete freezing-thawing cycles in seasonal frozen zone" and "Damage characteristics and mechanism of basalt fiber asphalt mixture under water-temperature coupling effect",the pavement performance,meso-properties,low temperature properties,acoustic emission properties,viscoelastic properties at high and low temperatures,fatigue properties and the trend of these propert ies in freeze-thaw cycles of basalt fiber asphalt mixtures are studied in this paper.Moreover,the prediction model of universal freeze-thaw damage evolution is established,and the damage mechanism of freeze-thaw cycles is demonstrated.It is of great theoretical significance and engineering application value to decrease the influence of freeze-thaw cycles on asphalt pavement and promote the application of basalt fiber asphalt concrete pavement.The specific research work carried out in this paper is as follows:1.SMA-13 asphalt mixture was modified with basalt fiber,and basalt fiber asphalt mixture and common lignin fiber asphalt mixture were prepared.Under freeze-thaw cycles,the damage regularity of common pavement performance indexes of two asphalt mixtures is studied.The test indexes include Marshall stability,compressive strength,splitting strength,indirect tensile stiffness modulus,low-temperature splitting strength,low-temperature bending strength and strain.Based on the damage and reliability theory,the damage evolution model of asphalt mixture under freeze-thaw cycles is established.The service life of asphalt mixture in seasonal frozen zone is predicted based on road performance test in outdoor environment.The influence of basalt fiber on the model index of asphalt mixture and the actual service life of asphalt mixture are explored.2.Based on digital image processing technology,the mesoscopic characteristics of basalt fiber asphalt mixture under freeze-thaw cycles are studied.The mesoscopic voids are divided into three categories: large,medium and small,which characterize the effects of frost heave force and water erosion,and analyze the extent of each damage effect in the freeze-thaw cycles.The mesoscopic characteristics of asp halt mixture under freeze-thaw cycles were explored,the damage mechanism of freeze-thaw cycles to asphalt mixture was characterized,and the improvement effect and mechanism of basalt fiber on asphalt mixture were analyzed.3.The low temperature crack resistance performance under freeze-thaw cycles was studied and monitored by acoustic emission technology.The splitting strength,failure strain,stiffness modulus and strain energy index of the low temperature splitting test under freeze-thaw cycles were studied.A statistical damage constitutive equation describing the basalt fiber asphalt mixture under the damage freeze-thaw cycles was established,and the fitting effect of the constitutive equation was analyzed.The acoustic emission parameters obtained by acoustic emission test were used to analyze the development of micro-cracks inside the asphalt mixture during loading,and the effects of basalt fiber and freeze-thaw cycles on the micro-crack propagation law were analyzed.4.The high and low temperature viscoelastic properties of basalt fiber asphalt mixture and the changes of viscoelastic parameters under freeze-thaw cycles were studied.The uniaxial static creep test at different temperatures and under different stresses was used to analyze the effect of basalt fiber on the high temperature viscoelastic properties of asphalt mixture by Burgers creep model.The suitable temperature and stress conditions were selected to study the high temperature viscoelastic properties under the freeze-thaw cycles,and the effects of freeze-thaw cycles on the high temperature viscoelastic parameters were analyzed.The low-temperature bending creep test of trabecular beam under different stress conditions was used to analyze the effect of basalt fiber on the low-temperature viscoelastic properties of asphalt mixture.The creep compliance and relaxation modulus were transformed and the change of relaxation characteristics was analyzed.The suitable stress conditions were selected to study the low temperature viscoelastic properties of the asphalt mixture under the freeze-thaw cycles.The effects of freeze-thaw cycles on the low temperature viscoelastic parameters of basalt fiber asphalt mixture were analyzed.5.The high and low temperature viscoelastic properties of basalt fiber asphalt mixture and the fatigue performance changes under the freeze-thaw cycles were studied.The fatigue resistance of basalt fiber asphalt mixture was studied by trabecular four-point bending fatigue test.The influence of basalt fiber on the va riation of stiffness modulus,lag angle and dissipative energy during fatigue test was analyzed to clarify the improvement mechanism of basalt fiber on asphalt mixture fatigue performance.The fatigue life equation of basalt fiber asphalt mixture was determined by indirect tensile fatigue test.The indirect tensile fatigue test was used to analyze the fatigue performance change of basalt fiber asphalt mixture under freeze-thaw cycles,and the fatigue life equation of basalt fiber mixture under freeze-thaw cycles was established.