Research On Properties And Key Evaluation Index Of Stress Absorbing Layer Asphalt

Setting stress absorbing layer with modified asphalt is one of the measures of anti-reflective cracking in semi-rigid or rigid base asphalt pavement. Its special modified asphalt and mixture are critical to the performance of anti-reflective cracking. But at present, systematic study and the specification or guide for stress absorbing layer asphalt binder in China are still blank, this brings difficulties for the popularization and application of this new technology. Therefore, further research on the properties of stress absorbing layer asphalt binder is needed and specification for the asphalt binder is urgent. Relying on west traffic construction project research on composite pavement of stress absorbing layer, systematic studies on asphalt binder and mixture were carried on and influencing factors on the performance were analyzed. Based on the production practice, key control index and evaluation standard for stress absorbing layer asphalt binder were proposed.(1) Factors to performance of stress absorbing layer asphalt binder were analyzed, such as base asphalt, chemical components, asphalt grade, modifier type and dose, modification technology and storage conditions. Based on the micro observation and macro experiments, mechanism of interaction among modifiers was studied and explained. Then satisfactory modification program and technology were proposed. Stress absorbing layer modified asphalt has good high and low temperature performance, aging resistance and excellent elastic recovery properties.(2) Aiming at the shortage of existing evaluation system for modified asphalt, and combineing with function requirements, technic requirements for stress absorbing layer binder were recommended. Meanwhile representative modified aspahlt were selected, such as SBS modified asphalt, SBR modified asphalt, QP modified asphalt, GC modified asphalt, TPS modified asphalt, SAM modified asphalt and STR modified asphalt, and performances of these asphats at high and low temperature, temperature susceptibilitu, toughness and tenacity and elastic recovery capability before and after aging were studied and compared. Combineing with the changes of macroscopic properties index for aspahlt binder before and after aging, aging mechanisms of modified asphalt were studied by gel permeation chromatography and grey relevant method. And the results indicated that changes in molecular weight and dispersion degree of asphalt before and after aging are the most important factors influencing asphalt macroscopic properties.(3) Considering the function of stress absorbing layer in the pavement structure, penetration test for asphalt mixture at high temperature was proposed on the basis of relevant research. Calculation combined with the test, the influence of test conditions such as diameter of pressure head, specimen shape, loading rate, temperature, asphalt and grading type was discussed. Finally, a shear index for absorbing layer asphalt mixture at hight temperature was recommended. In addition, Grey relevant method was used to analyze the relationship between asphalt and mixture performance, and the key evaluation index for stress absorbing layer asphalt binder were recommended in the paper.