Study On Road Performance And Interlayer Performance Of Ultra-Thin Overlay Asphalt Mixture

In recent years,due to the large number of high-grade highways built in China in the early stage of maintenance and repair,China’s highway management strategy has gradually changed from "construction instead maintenance" to "cconstruction and maintenance".The maintenance of pavement has gradually become the key development direction of the highway industry.As a kind of traditional road maintenance and protection measures,the thin overlay had a wide range of applications in preventive maintenance of road.Compared with other preventive maintenance measures,although the ordinary thin layer has a good conservation effect,due to its hot mixing process and structural thickness,the cost-effectiveness is poor.The study used a finer-grained SMA-5 asphalt mixture as an ultra-thin overlay for application in preventive maintenance.This study started from the asphalt binder of ultra-thin layer,and used high-viscosity modified asphalt as the asphalt binder of ultra-thin overlay,and used GH-1 modifier to prepare different kinds of high-viscosity modified asphalt.And three major indicators test,60℃ dynamic viscosity test,dynamic shear rheological test and low temperature bending beam rheological test to compare the performance of different GH-1 modifier high viseosity asphalt.The results show that the increase of the amount of GH-1 modifier makes the penetration of modified asphalt lower,the softening point increased,the plasticity is gradually improved,the dynamic viscosity at 60℃ is effectively improved,the high temperature performance is continuously enhanced,and the low temperature performance improved.Subsequently,the optimum asphalt dosage of SMA-5 ultra-thin overlay asphalt mixture was determined by Marshall Test.The high performance,low temperature performance,water stability performance,anti-fatigue performance,anti-sliding performance and other road performance of SMA-5 mixture were studied that the performance was compared with the warm asphalt mixture.The results show that with the increase of the amount of GH-1 modifier,the high temperature performance,low temperature performance and fatigue performance of SMA-5 asphalt mixture are improved,water stability is better when the GH-1 content is 10%.The incorporation of EWMA warming agent improves the high temperature performance and fatigue performance of the asphalt mixture,while water stability and low temperature performance have been reduced to some extent.Furthermore,the Shear resistance between layers of ultra-thin overlay structure was studied.The inter-layer shear stress of ultra-thin layer overlay was analyzed by BISAR3.0,and the inter-layer shear resistance index of ultra-thin layer overlay structure was proposed.The optimum asphalt content was determined by the interlayer shear test to achieve the best shear performance between the layers,and the factors affecting the interlayer shear performance such as water,shear rate and temperature were studied and analyzed.The results show that as the loading rate increases,the interlayer shear strength increases gradually,and the different loading rates lead to different strains caused by interlayer failure.The shear loading rate of 50mm/min is closer to the interlayer damage;the ultra-thin overlay will be lead to a large reduction in the interlayer shear strength because of the treatment of water immersion and the increase of temperatureFinally,the viscosity temperature curve was drawn by the Brookfield viscosity test to determine the construction temperature of the ultra-thin overlay’s asphalt mixture.Considering the problem that the temperature of the ultra-thin overlay drops too fast during the paving process and the effective compaction time is short.Therefore,the finite element model of pavement temperature field is established by ABAQUS finite element software,and the variation of temperature field during the paving stage of ultra.thin layer is simulated.The effective compaction of warm mix and hot mix asphalt is calculated that the time is 9 minutes and 7.5 minutes respectively.It is also proposed to add a warming agent during the preparation of the ultra-thin overlay’s asphalt mixture to extend the effective compaction time of the ultra-thin layer,and the effective compaction time was verified by the indoor temperature measurement of the SMA-5 asphalt mixture.The results show that the simulation of the temperature field of the ultra-thin overlay asphalt mixture is not much different from the actual temperature drop trend of the asphalt mixture.