A Study On The Performance Improvement Of Cold Recycled Mixture With Emulsified Asphalt

Cold in-place recycling(CIR)has been gradually accepted and applied in China because of its environmental and economic benefits,in order to meet the different demands of the project,road performance of CIR mixture needs to be further improved.The improvement of CIR mixture lies on the modified emulsified asphalt,what is the breaking point of asphalt and mixture performance study.Firstly,based on the principle of asphalt emulsification and modification,ordinary emulsified asphalt and three types modified emulsified asphalt were prepared by colloid mill method in accordance with the technical requirements.The performance of the prepared product was studied by conventional performance detection method,time scanning test,repeated creep recovery test and multiple stress creep recovery test.The results show that the stability of modified emulsified asphalt is poor and the high temperature performance is improved.Two type modifier can help to improve the low temperature ductility.The temperature and stress sensitivity of modified emulsified asphalt is low,which shows better resistance to permanent deformation.Secondly,the CIR mixture is designed and the priority of design index is determined by variance analysis.The performance of mixture of different curing modes is compared at different time nodes to seek the reasonable curing modes.The feasibility of using fly ash and steel slag partly replace cement is discussed.It is found that the performance of the mixture is reduced in different degrees,especially the early strength of the steel slag is very low,and the substitution amount should be strictly controlled.Thirdly,after simulating the temperature conditions of the cold regeneration layer by finite element software.The high and low temperature performance of CIR mixture were evaluated with the advanced dynamic creep and the semi-circular bending test.The results show that the anti-rutting performance of modified CIR mixture is better,and the crack resistance of two type mixture is improved,and SEBS modified CIR mixture is prone to brittle fracture.Overall,one type mixture has best road performance.The micro structure of CIR mixtures mortar is investigated by processing a series of vertical and horizontal images from digital scanner,and the "thickness spectrum" is proposed to study the distribution of cement emulsified asphalt mortar in CIR mixture.The results show that the thickness spectrum,which can be fitted with the Weibull growth distribution model,reflect the thickness status of asphalt mortar well.The modified emulsified asphalt mixture exhibits better compaction performance in the longitudinal direction.The law of thickness spectrum development under the effect of high temperature creep loading was proposed,and the method of predicting the remaining service life of CIR pavement structure was put forward.Finally,a series of studies have been carried out on the connection of emulsified asphalt-mortar and mixture system.Utilizing principal component analysis,the principal component of the integrated system under the normal load in summer can be found.11 test indicators with high correlation can be used to evaluate the performance of emulsified asphalt products.Through the research of this paper,an effective way to improve the performance of CIR mixture is obtained from the angle of modified emulsified asphalt and its mixture,which is helpful for practical engineering application.