Study On The Properties Of Cement Lime-emulsified Asphalt Cold Recycled Mixture

The recycling of pavement materials is one of the key points to achieve the high quality construction of road transportation infrastructure and also the main way to develop green highway.It is estimated that more than 200 million tons of waste asphalt pavement are produced in China every year.If all these materials are reused,it can form an economic value of up to 60 billion yuan.Compared with recycled coarse aggregate,recycled fine aggregate contains more aged asphalt,mineral debris,water and dust pollutants,so it is difficult to reuse materials.These high value recycled fine aggregates rich in asphalt are in a state of low utilization for a long time,resulting in resource waste and environmental pollution.Based on emulsified asphalt cold mixing technology,this study studied the effect of lime cement on the performance of emulsified asphalt cold recycled mixture,and then concluded the complete reuse technology of recycled fine aggregate through laboratory experiments.From the property and function of the material,the recycled fine aggregate mainly fills the void formed between the coarse aggregate,thus affecting the macro performance of the mixture.Cement,as a commonly used active filler,has the properties of dry shrinkage and weak cracking resistance,while quick lime has low strength but expansive property.Therefore,studying the influence of the combined action of recycled fine aggregate and lime cement on the performance of emulsified asphalt cold recycled mixture has an important value for improving the road performance of Emulsified Asphalt Cold Recycled Mixture(EACRM).In this study,emulsified asphalt cold recycled mixture was designed by changing the content of recycled fine aggregate,and the performance of the mixture was studied under the optimum mix ratio.The high and low temperature properties of emulsified asphalt mortar were studied by changing the proportion of lime and cement by fixing the total amount of active filler.The properties of the mixture were studied by changing the proportion of lime and cement with100% recycled fine aggregate content.The main research conclusions are as follows:(1)The road performance of the mixture decreased with the increase of the recycled fine aggregate content.Compared with natural aggregate,the splitting strength,dynamic stability,flexural strain and bending stiffness modulus of the mixture with 100% recycled fine aggregate content decreased by 23%,45%,26% and 14% respectively.The content of recycled fine aggregate has little effect on the water stability of the mixture,and the ratio of wet and dry splitting strength of the mixture is greater than 89%.(2)With the increase of lime instead of cement,the high temperature performance of emulsified asphalt mortar decreases,but the low temperature performance is improved.Compared with cement,the coning degree of asphalt mortar at 70℃ increases by 100% and the shear strength decreases by 75%.At-24℃,creep stiffness decreased by 14% and m value increased by 26%.(3)With the increase of lime substitute cement,the strength and high temperature performance of the mixture decreased,while the water stability and low temperature performance increased.When lime is used to replace cement completely,the splitting strength of the mixture decreases by 19%,the dynamic stability decreases by 35%,the flexural strain and bending stiffness modulus increase by 6% and decrease by 10%,respectively.When lime was used to replace cement at 25% and 50%,the water stability was improved and the dry-wet splitting strength ratio was increased by 3%.The high and low temperature properties of asphalt mortar are directly related to the high and low temperature properties of mixture.The cone-in test results at 40℃ are most relevant to the rutting test results of the mixture,and the rheological test of the curved beam at-12℃ is most relevant to the low temperature bending test results of the mixture.The results provide a reference for the selection of recycled fine aggregate,lime and cement in the design of emulsified asphalt cold recycled mixture.The emulsified asphalt cold recycled mixture with 100% recycled fine aggregate and the emulsified asphalt cold recycled mixture with lime completely replacing cement still meet the requirements in the specification and the performance is relatively stable.