Design And Performance Study Of Vegetable Oil Warm Mix Recycled Asphalt Mixture Based On LEA

In order to realize the sustainable development of the road industry,the research on the recycling technology of RAP（Reclaimed Asphalt Pavement）has been paid more and more attention by various countries.How to restore the performance of RAP material surface aging asphalt is the key to achieve effective regeneration.Waste vegetable oil has the characteristics of low viscosity,high unsaturation and high thermal stability,and its rich in fatty acids,polycyclic aromatic hydrocarbons and other biomass component groups are very similar to the light oil components（saturates,aromatics）missing from aging asphalt.According to the component adjustment theory,waste vegetable oil can be used as a low viscosity oil for aging asphalt regeneration.At the same time,compared with thermal regeneration technology,warm mix regeneration technology can reduce energy consumption and carbon emissions in the process of asphalt mixture regeneration,and has good economic and environmental benefits.As a warm mix technology,LEA（Low-energy asphalt）technology uses the moisture of wet and cold fine aggregate to make hot asphalt foamed,so that the mixture can be mixed at about130°C,and the system has lower energy consumption and better economy.In this paper,the waste vegetable oil regeneration technology and LEA technology are combined to systematically study the performance influence mechanism,material design and road performance influence of the mixture,and the mixing process is optimized.The LEA-based vegetable oil warm mix recycled asphalt mixture（hereinafter referred to as warm mix recycled mixture）and its application technology are developed.Firstly,in order to reveal the influence mechanism of waste plant content and RAP heating temperature on the performance of warm mix recycled mixture,the migration depth of new-old asphalt under 0%,6%,8%and 10%waste plant oil content was analyzed by stratified extraction,molecular tracer and infrared spectroscopy.The changes of microstructure and functional groups of asphalt at 110°C,120°C and 130°C were analyzed by atomic force microscopy and infrared spectroscopy.The results show that waste vegetable oil can promote the migration of new asphalt in aged asphalt,and the migration depth increases with the increase of dosage,thus promoting the miscibility of new and old asphalt.Different regeneration temperatures have a great influence on the micro-morphology and micro-composition of asphalt.The morphology and hydroxyl and sulfoxide functional groups of recycled asphalt at 110°C are more obvious,the number of bee-like structures is the largest,the area is the smallest,and the hydroxyl and sulfoxide functional group index is the smallest.Secondly,the fifth grade water consumption is selected to mix the warm mix recycled mixture at 110°C,and the optimum water consumption W₁ is calculated by Marshall test.Five grades of water consumption were taken near W₁ to mix the mixture,the residual water content was measured and the test results were fitted.The optimum water consumption W₂corresponding to 0.5%residual water content was calculated,and the average values of W₁and W₂ were calculated,which was the final optimum water consumption.The results show that the optimum water consumption of the mixture is 1.42%,1.30%and 1.20%respectively under 20%,30%and 40%RAP content,which can not only ensure the Marshall test design index of the mixture,but also meet the engineering experience of LEA technology with 0.5%residual water content.Then,in order to analyze the influence of waste vegetable oil content and RAP heating temperature on the road performance of warm mix recycled mixture,the high temperature performance,low temperature performance and water stability of the mixture were investigated by rutting test,low temperature trabecular bending test and freeze-thaw splitting test.The results show that when the content of waste vegetable oil is increased from 6%to10%,the low temperature performance and water stability of warm mix recycled mixture are continuously improved,and the improvement range is also increasing.The high temperature performance is reduced,but it still meets the requirements of the specification.Considering the high,low temperature and water stability of the mixture,the optimum content of waste vegetable oil is determined to be 10%.When the RAP heating temperature increases from110°C to 130°C,the low temperature performance and water stability of the warm mix recycled mixture continue to decline,the decline is also increasing,and the high temperature performance is improved.The RAP regeneration temperature is 110°C.The above optimum dosage and regeneration temperature are consistent with the microscopic mechanism analysis.Finally,in order to improve the workability of warm mix recycled mixture,the mixing process was optimized by gel permeation chromatography combined with layered extraction test results.It was found that the improved mixing process can improve the new-old asphalt fusion effect of warm mix recycled mixture.The road performance of the mixture under the two mixing processes was tested and studied.The results show that although the road performance of the mixture decreases with the increase of RAP content,the high temperature performance,low temperature performance and water stability of the mixture in each group are significantly improved by the improved mixing process.The dynamic stability of the mixture under 40%RAP content increased by 18.9%,the maximum flexural strain increased by 5.7%,and the splitting strength ratio increased by 1.2%.