Design And Performance Optimization Of Warm Mix Recycled Asphalt Based On Compatibility

With the large-scale renovation of asphalt pavement in our country,the recycling of waste asphalt pavement aggregate has become a hot issue in recent years.Among a variety of regeneration methods,warm-mix regeneration technology has been widely used because of its lower mixing temperature compared with hot-mix regeneration technology,which can save a lot of resources,and it also has higher road performance than cold-mix regeneration.In order to improve the recycling rate of waste materials,it is an inevitable trend to increase the blending ratio of RAP in the mixture.At present,in the process of warm mix regeneration,there are few regenerating agents added to restore the performance of RAP materials,which results in the difficulty of greatly improving the low temperature performance of the regenerated materials,which limits the increase of the RAP blending ratio.In order to increase the mixing ratio of RAP and ensure the road performance of the warm-mix recycled asphalt mixture,the performance of RAP asphalt is restored by using a regenerating agent.Under this circumstance,the compatibility of the performance between the regenerant,the warm mix agent and the base asphalt will affect the performance.The purpose of this paper is to analyze the performance difference between different combinations of compatibility and finally obtain the best combination of compatibility.First of all,choose the warm mixing agent,regenerating agent from different manufacturers and 90# matrix asphalt from different oil sources as raw materials.Rotating film oven aging test(RTFOT)and pressure accelerated aging test(PAV)were used to prepare asphalt samples with different degrees of aging.Based on the three major indexes of asphalt and the viscosity test,the optimal mixing amount of warm mix agent and regenerant under different conditions is determined.Secondly,based on the method of atomic force microscope(AFM),the main indicators are the nano-roughness,adhesion and "bee-shaped" structure change trend of the asphalt surface to analyze the degree of fusion and diffusion between different regenerants,warm mix agents and asphalt.And use this to judge the compatibility relationship between different combinations.At the same time,combined with Fourier Infrared Spectroscopy(FTIR)test methods,through the change characteristics of the characteristic functional group index of asphalt materials under different conditions,the regeneration mechanism and aging mechanism of warm mix asphalt are quantitatively evaluated,and different warm mixes and regenerants are further analyzed.Compatibility relationship with different asphalts.Third,the dynamic shear rheological test(DSR)is used to analyze the rheological properties of warm-mix regenerated asphalt during the aging and regeneration process.Draw complex shear modulus and phase angle master curves according to the principle of time-temperature equivalence,analyze the viscoelastic properties of asphalt materials at different temperatures,and clarify different regenerants and warm mixes through index parameters such as rutting factor,fatigue factor and strain recovery rate The effect of the agent on improving the high temperature,low temperature and fatigue performance of the aged asphalt,and to evaluate the compatibility relationship between different warm mix agents and regenerants and different asphalts,and then propose the best comprehensive performance of the compatibility combination.Finally,based on the variability characteristics of the aged asphalt content in RAP and the variability of each grade,the RAP recycled mixture design method is proposed,and the best comprehensive performance combination is used to study the performance of the mixture.Taking the water stability and low temperature performance of the recycled asphalt mixture as the main evaluation indicators,through comparative tests,comprehensively evaluate and verify the characteristics of the influence of the combination of warm mix agent and regenerant on the performance of warm mix recycled asphalt mixture.The main research results are as follows: 1)Analyze the microscopic behavior and aging mechanism of different regenerants,warm mix agents and different combinations of base asphalt with the aid of AFM and FTIR to obtain a combination of good compatibility;2)Compare the rheological properties before and after aging through DSR to determine the compatibility combination with good rheological properties and viscoelastic properties,and at the same time better microscopic properties;3)The lowtemperature trabecular test and the freeze-thaw splitting Marshall test are performed to verify that the warm-mix regenerated asphalt mixture under the best compatibility combination has the effect of improving the low-temperature performance of the nonadmixed regenerant.