Study On Performance Of Foamed Asphalt Cold Recycled Mixture Based On Virgin-Aged Asphalt Fusion Characteristics

Foamed asphalt cold recycling technology is widely used due to energy saving,environmental protection and low engineering cost.However,the research on foamed asphalt cold recycled mixture is not sufficient.Most of them are based on the macroscopic properties of the mixture.By changing the amount of cement,Optimize grading and other methods to improve the road performance of the mixture.However,the internal structure of foamed asphalt cold recycled mixture is complex,and its performance is affected by many factors such as foam asphalt cement adhesion performance,RAP surface asphalt aging degree and RAP temperature.Only the research on the roadway performance can not reveal the foam asphalt.The intrinsic mechanism of poor performance of cold recycled mixes.In view of this,based on the fusion bonding characteristics between foamed asphalt and aged asphalt,the performance of foamed asphalt cold recycled mixture was studied.Firstly,the effects of foaming temperature and foaming water consumption on the foaming characteristics of asphalt were studied.The expansion ratio and half-life were used as the evaluation indexes of foaming effect.Through the analysis of the foaming test results,the effects of foaming temperature,foaming water consumption on expansion ratio and half-life and their correlation were obtained,and the optimum foaming temperature and foaming water consumption were determined.Secondly,the orthogonal design method was used to study the effects of powder-to-gel ratio,asphalt aging degree and RAP temperature on the adhesion characteristics of foamed asphalt and aged asphalt from the perspective of Virgin-Aged Asphalt fusion bonding.Among them,the adhesion strength between foamed asphalt cement and aged asphalt was obtained by self-testing equipment.The range analysis and variance analysis showed that the ratio of powder to rubber had the greatest influence on the adhesion performance of foamed asphalt cement and aged asphalt.It is the RAP temperature,and the degree of asphalt aging has the least impact.The foamed asphalt cement with a powder to rubber ratio of 2:1 has an RAP temperature of 50? and an aging degree of 85 min.The aged asphalt with RTFOT+10 hPAV has the best adhesion performance.Furthermore,the mix design of the foamed asphalt cold recycled mixture was carried out,and the optimum oil-stone ratio and the optimal mixing water consumption were determined through experiments.Based on the results of the Virgin-Aged Asphalt bonding test,it is found that the powder-to-binder ratio has the greatest influence on the adhesion performance of foamed asphalt cement and aged asphalt.Therefore,the design of different powder-to-binder ratio recycled mix,combined with foamed asphalt cold-recycled mix dry/wet splitting strength test Make sure the optimum ratio of powder to glue is 2:1.Finally,based on the research results of the complete adhesion failure of the foam asphalt cement and the aged asphalt failure interface in the Virgin-Aged Asphalt bonding test,three different mixing processes were designed,using freeze-thaw splitting,rutting and unconfined compressive strength.The effect of the mixing process on the road performance of the foamed asphalt cold recycled mixture was analyzed.The results show that the mixing process has a significant impact on the performance of the cold recycled mixture.