Study On Material Composition Optimization And Interlayer Bonding Properties Of Cape Seal

As a composite pavement structure combined with Chip Seal and Micro-surface,Cape Seal is an efficient pavement maintenance method,which combines the advantages of both individual constituents.However,this efficacy is easily lost with the sub-layer when it is under traffic load.Moreover,RAP has low utilization due to its inadequate performance.Therefore,in view of the adhesive failure between the Cape Seal and the sub-layer as well as the low recycling efficiency of the waste asphalt mixture,the RAP is applied to the Cape Seal.The material composition of the Cape Seal is further optimized and its bond performance,studied.Not only is it environmentally friendly by helping to reduce pollution,it also helps to realize a reasonable and sustainable recycling of resources.According to the empirical calculation method,the recommended amount of hot asphalt in the current maintenance technical specification was optimized.When making the Cape Seal specimen,the volume of matrix asphalt was 1.2-1.4kg/m~2,SBS modified asphalt was 1.2-1.4kg/m~2,asphalt rubber was 2.2～2.4kg/m~2,and modified emulsified asphalt was 2.0～2.2kg/m~2.By means of inter-laminar pull-out,and direct shear and torsional shear tests,the high temperature curing method for preparing the specimen of Cape Seal was proposed.The results showed that when the chip coverage is in the 88%～92%range,and the combination of upper and lower layers is 4.75～9.5mm Chip Seal+MS-3 Micro-surfacing,the bond performance of Cape Seal is better.On this basis,in order to achieve a reasonable use of RAP and enhance the bonding and wrapping performance between asphalt and stone,the RAP pre-wrapping technology was proposed,and its preparation parameters were determined through an orthogonal test.Based on the determined chip quality,30%RAP is selected to replace the chip and the new stone is mixed at 160℃ for 90s before paving.By analyzing the surface properties and bonding properties of Cape Seal with RAP pre-wrapped,the feasibility of RAP pre-wrapped technology was illustrated.Finally,with the help of PFC,the two-dimensional discrete element model of Cape Seal pavement structure was established,and the mechanical response of the interface between Cape Seal and sub-layer under different wheel pressure and speed was studied.The maximum tensile stress and shear stress calculated by simulation and the tensile strength and shear strength of three types of Cape seal obtained by test were compared and analyzed,and the appropriate vehicle weight and speed were recommended.The results further verified the feasibility of RAP pre-wrapping technology and suggested that the road limit speed should be appropriately increased,with 60～80km/h suggested as the speed limit.