Investigation On High Content RAP Hot Recycled Asphalt Mixture Based On SMC Warm Mix Agent

The proposal of dual carbon strategic goal makes people pay more attention to environmental protection and sustainable development,so asphalt mixture regeneration technology has been paid more and more attention and application in road engineering.In order to solve the problem of low RAP content in hot recycling technology,warm mix agent was used to reduce the heating temperature difference between old and new materials in the scope of hot recycling technology,and reduce the viscosity of asphalt,and improve the utilization rate of RAP,and solve the problem of pollution and large consumption of hot mix recycled asphalt pavement.In this paper,SMC warm mix regeneration agent was used to regenerate SBS modified asphalt with different aging degrees,and hot recycled asphalt mixture with high content RAP was prepared,and the road performance and strength fatigue performance of the mixture were studied.It provided a reference for realizing the hot recycling of mixture with high content RAP and applying SMC warm mix regeneration agent to the regeneration technology of pavement.Firstly,SBS modified asphalt with different aging degrees were prepared based on simulated aging test in laboratory.Then SMC warm mix regeneration agent was added into the aging asphalt with different content for regeneration.The high and low temperature rheological properties of aging and recycled asphalt were studied by dynamic shear and low temperature bending creep test.The corresponding visual surface and model were established by MATLAB to establish the relationship between the amount of SMC regeneration agent and the aging degree of aging asphalt and the rheological property index,so as to obtain the optimal amount of regeneration agent corresponding to the asphalt with different aging degrees.The regeneration mechanism of SMC was revealed by infrared spectroscopic test and the regeneration effect of SMC was verified by scanning electron microscope test.Secondly,the recycled RAP was extracted and screened,the mineral aggregate gradation and oil stone ratio of RAP were determined.The AC-20 grading was used for regenerative asphalt mixture ratio design,and the recycled asphalt mixture with 50%and 60%content RAP were prepared.The water stability,high temperature stability and low temperature crack resistance tests were carried out,so the road performance of recycled asphalt mixture with different content RAP was studied.Finally,the indirect tensile strength tests at different loading rates and temperatures were carried out to reveal the relationship between the strength of recycled asphalt mixture with different content RAP and loading rate and temperature.The unified strength model of recycled asphalt mixture was constructed by dimensionless method from the variation relationship between indirect tensile strength ratio and loading rate ratio.The fatigue properties of two kinds of recycled asphalt mixtures were analyzed and compared by indirect tensile fatigue test,and the relationship between the fatigue life of recycled asphalt mixtures and the stress level and stress ratio was established by phenomenological method.To sum up,this study evaluated the regeneration effect of SMC warm mix regeneration agent from the aspects of road performance,strength and fatigue performance of recycled asphalt mixture and recycled asphalt,which provided a new way to achieve the hot recycling of asphalt mixture with high content RAP,and had significant environmental and economic benefits.