Study On Durability Of High Modulus Agent-SBR Composite Modified Asphalt Mixture In Seasonally Freezing Area

High modulus admixture is a modified material widely used to improve the high temperature stability of asphalt pavement.However,due to the high modulus of a single modified high modulus asphalt mixture,the road surface is prone to cracks at low temperatures.The addition of SBR modifier is beneficial to improve the low temperature crack resistance of asphalt pavement.Therefore,this paper proposes a combination of high-modulus agent and SBR modifier to give full play to their respective advantages in view of the climatic characteristics of the seasonal frozen area,and conducts research on the performance of the high-modulus agent-SBR composite modified asphalt mixture.The main research contents of the paper are as follows:First of all,the technical performance tests were performed on the raw materials used in the test.AC-13 mixture was used as the mineral aggregate grading standard.Three kinds of high modulus agents(Lubao made in China,PRM made in France and Duroflex made in Germany)were selected to modify with SBR to make composite modified asphalt mixture.Through the test of compression modulus and uniaxial compression dynamic modulus,the change rule and correlation of static modulus and dynamic modulus of different modified asphalt mixtures were studied.According to time-temperature equivalence principle,the dynamic modulus master curves of different kinds of modified mixtures are established,and their mechanical properties in the full frequency range are compared and analyzed.The results show that the high temperature performance and low temperature performance of the composite modified asphalt mixture is significantly improved,and the effect of adding Lubao high modulus agent is the best.Secondly,according to the research results of different mechanical parameters of the asphalt mixture,based on the Central Composite Design method of Response Surface Method,the response surface is established by taking the Lubao high modulus agent content and the SBR content as the influencing factors,and the dynamic stability,flexural tensile strength,critical flexural strain,freeze-thaw splitting strength ratio,and immersion residual stability as the response indicators.According to the index constraints and performance requirements,the optimal content of Lubao high modulus agent is 0.44%(accounting for the quality of asphalt mixture),and the optimal content of SBR modifier is 3.52%.The predicted value of the model is verified by the actual test.The results show that the response surface method can fit the road performance response index of the composite modified asphalt mixture better.Finally,according to the test results of dynamic modulus,the creep characteristics of asphalt pavement under the combined action of temperature and load are studied by using COMSOL software;On this basis,the influence of different modulus and permeability of surface layer on pore water pressure,vertical stress and horizontal stress of asphalt pavement under the combined action of water temperature load is analyzed.In conclusion,this study is of great significance for the popularization and application of high modulus agent-SBR composite modified asphalt mixture in the seasonal freezing area and the improvement of the durability of asphalt pavement.