Research On The Shear Stress Of Inter-layer And Shear Strength Of Tack Coat Materials Of CRC+AC Composite Pavement

Along with the rapid economic development, traffic volume and traffic load alsoincrease. Road transport appears the new features of multi-axis, over loading, heavypressure of wheel load, highly channelizing and a common phenomenon ofoverloading. Thess factors result in the distruction of the road ahead of time andcausing huge economic losses. So it is necessary to adopt a more reliable pavementstructure to bear the huge traffic load. In the idea, continuously reinforced concrete(CRC)+asphalt concrete (AC) composite pavement is put forward to adapt to theheavy-load traffic of the pavement. The CRC plays the role of the main load-bearing,and the surface AC layer as functional layer is to improve the driving comfort. TheCRC+AC composite pavement is of the advantage with the overall high strength,strong load-bearing capacity, long sevice life and durability and convenientmaintenance of the surface layer. It is one of the development direction of heavy-loadtraffic and long-life pavement structure, causing widespread concern around theworld.There is obvious difference in the modulus and the thickness between CRC layerand AC layer. Under the driving load and the influence of the external environment,the road surface damages for example slipping, folding and rutting are tend to occurbecause of the lack of the inter-layer shear strength, so it is necessary to take moreeffective measures to ensure the inter-layer bonding.According to the damage characteristics of composite pavement, this paperpresents the shear stress index as the index of the structional design. Base on thetheory of elastic layered system, this paper analyzes the variation of inter-layer shearstress when changing the parameters of pavement structure or materials usingBISRA3.0pavement structure calculation software. Results of the analysis indicatethat positions where shear failure is most likely to occur are located at the edge of thewheel along the center of the wheel. It is most favorable to stability of the pavementstructure when inter-layer contact in good condition. Thickness of AC layer has asignificant effect on inter-layer shear stress and reasonable thickness of AC layer is8cm~12cm. Inter-layer shear stress increase substantially under the overloading, andhigh temperature and overloading is very adverse to inter-layer. Within the AC layer,maximum shear stress is located in the upper part of the layer where shear failure is likely to occur. Laboratory shear tests are carried out on several materials of tack coatto analyze their performance. Results of shear tests indicate that the use ofstyrene-butadiene-styrene (SBS) polymer modified asphalt with geotextile betweenthe CRC and AC layers may improve the inter-layer shear resistance. This paperrelying on the project in Changsha to Xiangtan expressway explores the keytechnologies of composite pavement inter-layer contruction: baring technology ofCRC layer surface and synchronous surface dressing technology.