Research On Cracking Characteristics Of Warm Mix Rubber Powder Modified Asphalt Mortar Under Complicated Cli Matic Conditions

With the development of the national economy,car ownership continues to increase,and people’s demand for roads is also increasing.As the main material of pavement,asphalt mixture is not only affected by aging for a long time,but also easy to crack and cause damage in the low temperature season.The rubber powder modified asphalt material exhibits good high and low temperature performance,and has been widely concerned in recent years,and because of a series of environmental protection problems brought by hot mixing technology,many scholars continue to study the warm mixing technology.As an important part of the rubber powder modified asphalt mixture,the rubber powder modified asphalt mortar has an important influence on the road performance of the mixture.Therefore,this article explores the low-temperature cracking characteristics of warm-mix rubber powder modified asphalt mortar under the influence of complex climatic conditions from the macro and meso scale.In this paper,SDYK surface-active warm mix rubber powder modified asphalt mortar(CR-WMA-S)and hot mix rubber powder modified asphalt mortar(CR-HMA)are selected as the research objects,based on the digital image correlation method(Digital Image Correlation,referred to as DIC),to explore the low-temperature cracking characteristics of two asphalt mortars under the combined effects of aging and freeze-thaw cycles.Firstly,based on the three-point bending test of two rubber powder modified asphalt mortars,the damage changes are explored from the flexural tensile strength,flexural stiffness modulus,flexural strain energy density,fracture toughness,and strength loss rate.The cracking characteristics of rubber powder modified asphalt mortar at the macro scale;secondly,combined with DIC technology to collect the displacement field and strain field of the mortar specimen during the loading process,determine the cracking position,select the research point,and analyze the horizontal and vertical directions of the research area.Analyze the characteristic cloud image in the straight direction;then,use the displacement field and strain field to analyze the variation of the displacement and strain near the crack initiation point with time,and obtain the critical crack tip opening displacement(Crack Tip Opening Displacement Critical,referred to as CTODC)and horizontal strain Density,analyze the cracking characteristics of mortar trabeculae from the meso scale;finally,based on the macro and meso scale,analyze the correlation between the fracture toughness JC of the load-displacement curve and the critical crack tip opening displacement of the horizontal strain-time curve.The results show that the anti-cracking properties of CR-HMA and CRWMA-S rubber powder modified asphalt mortars show a decreasing trend with the combined action time of aging and freeze-thaw cycles and the increase of salt concentration;no matter what The crack resistance of CR-WMA-S under salt concentration conditions is better than CR-HMA;the combination of DIC technology and three-point bending test is used to analyze the cracking performance of warm-mix rubber powder modified asphalt mortar with different compound action time and salt concentration It has good reliability;it is recommended to use fracture toughness as the macroscopic cracking characteristic index of rubber powder modified asphalt mortar,and strain energy density as the microscopic cracking characteristic index of asphalt mortar.