Study On The Performance Of SBR-SiO₂ Composite Modified Emulsified Asphalt Cold Recycled Mixture

Under the repeated action of vehicle loads and the long-term influence of harsh environments,asphalt pavement needs to be maintained or even reconstructed,which will inevitably generate a large amount of recycled asphalt(RAP).Recycling RAP will help save resources,protect environment and reduce road construction costs.Emulsified asphalt cold recycling technology due to its unique construction technology,the RAP utilization rate is as high as 100%,has been widely used in road construction.However,there are still many problems with emulsified asphalt cold recycled mixture,such as frequent rutting and cracking within the road design service life.It is precisely because of these problems that emulsified asphalt cold recycled mixture is restricted to be applied and popularized to a higher level of pavement structure.Based on the above reasons,this paper uses SBR latex and nano SiO2 sol to modify emulsified asphalt to prepare high-performance composite modified emulsified asphalt.Cement and polyester fiber are selected as fillers to explore the influence of cement and fiber on the road performance of cold recycled mixture.The following is the core content of this paper:Firstly,SBR modified emulsified asphalt was prepared,analyze the three indexes of evaporation residues,and determine that the optimal SBR latex content is 3.5%.Prepare SBR-SiO2 composite modified emulsified asphalt by adding different amounts of SiO2 sol.Test its performance,including general performance of evaporation residue,rotational viscosity test,DSR test and BBR test,and the optimal SiO2 sol content is determined to be 3.0%.The infrared spectrum analysis shows that the addition of the two modifiers is mainly physical change;the scanning electron microscope analysis shows that SBR and SiO2 form stable agglomerates to improve the performance of asphalt.Secondly,the mix proportion design of the mixture is carried out.The main contents include:mineral aggregate mix proportion design,determining the best moisture content and determining the best asphalt dosage.The general performance tests show that RAP has been aged,used as "black aggregate".Determination of optimum moisture content by geotechnical compaction test,and determination of optimum emulsified asphalt content by splitting test.The results showed that the optimum moisture content is 4.0%,and the optimum amount of emulsified asphalt is 3.9%.Finally,the effects of different amounts of cement and polyester fiber on the mechanical and road performance of cold recycled mixture are analyzed.The test results show that cement can improve the high temperature performance and water stability performance of the mixture,and weaken the low temperature performance;With the increase of fiber content,the high-temperature,low-temperature and water stability performance of the mixture showed a trend of first increasing and then decreasing.In this paper,it is suggested that the contents of cement and fiber are 1.5%and 0.3%,respectively.