To explore the interlayer bonding behavior of ultra-thin wearing course composite structures,the waterborne epoxy emulsified asphalt was prepared as the bonding layer material by using the pre-emulsification and post-modification method.AC-13 gradation mixture was used to simulate the original pavement.AC-10,SMA-10,and UWM-10 were selected as ultra-thin wearing courses.The direct shear tests were conducted to determine the load-displacement fitting curves of various composite specimens,obtaining performance indicators,e.g.,interlayer shearing strength,peak displacement,interlayer stiffness,and interlayer bonding energy.The influence of factors(e.g.,sprinkling amount,test temperature,binder type,and ultra-thin wearing course gradation)on interlayer bonding behavior was investigated.The result indicates that the optimal sprinkling amounts for AC-10,SMA-10,UWM-10 are 0.9,1.2,0.9 kg/m2 respectively.There is little effect of waterborne epoxy resin addition on the optimal sprinkling amount.The environmental temperature significantly affects the interlayer mechanical property of composite specimens.As the temperature increases,the shear strength,shear stiffness and interlayer bonding energy of composite specimens decrease by 65％-90％.The bonding behavior of waterborne epoxy emulsified asphalt is significantly superior to that of blank specimen.The average shear strength,shear stiffness,and interlayer bonding energy of modified bonding layer are 2.5,2.1,2.4 times of those of blank specimen.At higher temperatures,these indicators are 3.3,2.5,3.5 times of those of blank specimen.The addition of waterborne epoxy resin significantly improves the high temperature stability of bonding layer,and makes the thermoplastic emulsified asphalt develop in the thermosetting direction.Among 3 types of ultra-thin wearing courses,SMA-10 and UWM-10 exhibit superior bonding behavior,while the bonding behavior of AC-10 declines sharply when the pavement temperature reaches 35 ℃.
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