Study On The Application Of High Elastic Modified Asphalt And Mixture In Bridge Deck Pavement In High Altitude Mountain Area

High elastic modified asphalt concrete,as a new kind of pavement material,has good elastic properties,excellent rutting resistance and tensile stress absorbed/diffused performance,which can significantly alleviate the deflection of bridge deck and crack,when it is applied to to the high altitude mountain cement concrete bridge deck pavement where there is a strong ultraviolet radiation,much rain,and large temperature difference.However,the influence of strong ultraviolet radiation to high elasticity modified asphalt remains uncertain,and the repeated freeze-thaw cycles in winter aggravates the damage of asphalt pavement.In addition,modified asphalt waterproof adhesive layer has a lower low-temperature bonding performance and insufficient shear strength.Aiming at the above problems,the indoor ultraviolet accelerated irradiation test was employed and the scheme of ultraviolet aging resistance was puts forward,and the performance of high elastic modified asphalt concrete under freeze-thaw effect was assessed.The high elastic modified asphalt was applied to the waterproof layer and the design method of waterproof bond-stress absorbing layer was put forward to provide a reference for engineering practice.Firstly,the properties of high elastic modified asphalt and SBS modified asphalt was test.After 259h exposure in homemade indoor accelerated ultraviolet radiation room,which simulated six months outdoor exposure,the overall chemical composition of high elastic modified asphalt tended to stabilize,and the aging trend slowed down.Tests showed that the optimum addition of TiO2 and SiO2 in the high elastic modified asphalt was 2%and the optimum mixing time was no less than 20min,where it showed good compatibility with the asphalt and the dynamic stability reduced 13.8%and 14.9%respectively,and thus decreased the influence of ultraviolet to the asphalt effectively.Secondly,the freeze-thaw cycle test was designed according to the climatic conditions in this area,high temperature stability,water resistance and other pavement performance of the high elastic modified asphalt concrete and SBS modified asphalt concrete were compared.The results showed that after 15 freeze-thaw cycles,the freeze-thaw damage of the bending stiffness modulus was less than 30%;After 16 cycles,its TSR was more than 80%;And after 20 cycles,the void volume of its mixture increased no more than 1%,which can effectively reduce the temperature fatigue and void volume expansion caused by freeze-thaw cycle damage in high altitude mountain.Finally,two kinds of waterproof layer,"cement concrete slab+ high elastic modified asphalt+ pavement layer" and "cement concrete slab+ high elastic modified asphalt chip seal+pavement layer",were put forward.Mcleod method,which was usually used in chip seal,was modified and applied to the waterproof system two.The optimum asphalt spreading amount of two kinds of waterproof layer were decided through pullout test and shear test.The results showed that the low-temperature bonding performance of the waterproof layer with high elastic modified asphalt was greatly improved,and the shear stress improved by 34.7%when high elastic modified asphalt chip seal was employed in high altitude mountain area.