Research On Performance Of Waste Vegetable Oil Preformed Foamed Asphalt Cold Recycled Mixture

In recent years,the concept of green development has been deeply rooted in the hearts of the people,and building a resource-saving and environment-friendly society has become the general trend.The road construction industry also responded to the call of the state and conducted a lot of research on the recycling of waste road materials.Among them,the use of foamed asphalt for cold recycling technology of waste asphalt pavement is widely used in large and medium scale repair and regeneration projects of all grades of highways and city roads because of its high mixing rate of old materials,construction pollution and small discharge.However,the current foamed asphalt cold recycling technology does not fully consider the performance recovery of the aging asphalt in the waste pavement materials.The road performance of the recycled mixture is worse than that of the hot recycled asphalt mixture,which can only meet the use requirements of the pavement base layer,which restricts application of foamed asphalt cold recycled mixture.In order to improve the pavement performance of foamed asphalt reclaimed mixture,this study aims at innovating the use of waste vegetable oil with low viscosity and high degree of unsaturation as the pre wetting agent,pre treating the waste asphalt pavement materials,recovering the performance of the aging asphalt,and combining with the foamed asphalt,so that the recycled asphalt mixture can meet the performance requirements of the surface asphalt mixture.First of all,in order to select the indoor simulated aging asphalt which is similar to the original aging asphalt,the foaming test of three kinds of base asphalt(Asphalt-A,Asphalt-B,Asphalt-C)was carried out to determine that the base asphalt with the best foaming effect was Asphalt-C.Using this base asphalt to perform RTFOT and PAV aging tests to obtain simulated aging asphalt with different degrees of aging.Taking the performance of the aging asphalt in the asphalt pavement milling waste asphalt mixture as the criterion,it is determined that the indoor asphalt aging simulation method is RTFOT heating at 165℃,75 min,PAV110℃,2.1MPa,40 h to prepare aged asphalt.Secondly,in order to study the influence of waste vegetable oil pre-lubricant on the performance of aged asphalt,the pre-moistening amount of waste vegetable oil is 5.0%,6.0%,7.0%,and the pre-moistening time is 20 min,40min,60 min.At the macro level,three indicators,viscosity,surface free energy and other indicators are used to analyze and study the influence of waste vegetable oil pre-lubricant on the macro performance of aged asphalt.It is found that the addition of waste vegetable oil pre-lubricant can effectively soften aging asphalt and reduce aging.The viscosity of asphalt improves the temperature sensitivity and crack resistance of aged asphalt;The effects of waste vegetable oil pre conditioner on the microstructure and morphology of aged asphalt were analyzed by using component change rate,carbonyl index(CI),sulfoxide index(SI)and bee like structure of asphalt surface.It was found that the addition of waste vegetable oil pre conditioner could supplement the components missing in asphalt aging and inhibit the oxidation reaction of benzyl and sulfide to increase the bee like structure of asphalt surface and improve the surface roughness caused by asphalt aging.Finally,through a comprehensive analysis of the macro and micro perspectives,it is determined that the optimal pre-wetting amount of waste vegetable oil pre-wetting agent is 7.0%,and the pre-wetting time is 60 minutes;Finally,in order to explore the influence of waste vegetable oil preconditioning foamed asphalt cold recycling mixture on the amount of waste vegetable oil prepared by pretreated waste asphalt mixture,the standard mix compaction test and splitting test were used to determine the mixture ratio of waste vegetable oil preformed foamed asphalt cold recycling mixture under different waste vegetable oil pre conditioner dosage.By using dynamic stability,maximum flexural strain,residual stability and freeze-thaw splitting strength as evaluation indicators to evaluate high temperature performance,low temperature crack resistance and water stability,the test results show that the blending of waste vegetable oil can improve Although the low-temperature anti-cracking performance and water stability of foamed asphalt mixture,the high-temperature performance is not as good as the improvement effect of lowtemperature performance and water-stable performance,but it still meets the high-temperature performance requirements of surface materials in the specification.