Structure Optimization Design Of Asphalt Pavement Containing Emulsified(foamed)asphalt Cold Recycling Layer

In recent years, the early construction of asphalt pavement in our country has graduallyentered maintenance period, and was followed by a huge amount of reclaimed asphalt mixture.At the same time, with the increasing depletion of resource as well as people’s awareness ofenvironmental protection, makes the asphalt pavement recycling technology gradually beingextended applied. Especially in the21st century, the entity engineerings using cold recyclingtechnology are in full swing up. The current study of cold recycling technology mostlyconcentrated on the mix design, construction method, road performance, etc. But there areless study on design parameters、fatigue characteristics and other aspects of cold recyclingmixtures, especially thickness determination of pavement structure containing cold recyclinglayer usually depends on construction experience and there’s little theoretical basis to follow.Therefore, the paper obtained design parameters and control indicators through laboratorytesting, and on this basis to optimize the design of structure layer containing cold recyclingmixture, which has a great significance.In order to improve utilization of reclaimed asphalt mixture, the paper used two tranchesold material common used in Beijing to design emulsified(foamed) asphalt cold recyclingmixture with80%and100%RAP and further study theirs technical performance. Testsshowed that technical indicators of these two RAP percent cold recycling mixture withemulsified (foamed) asphalt fully meet the requirements of lower layer.Basing on the mixture design, the paper studied the change law of compression resilientmodulus of cold recycling mixture undering four different temperature and recommendedcompression resilient modulus ranges of emulsified(foamed) asphalt cold recycling mixturewith80%and100%RAP at15℃and20℃for Beijing area.The paper taked the controlled strain loading model to study fatigue characteristics ofcold recycling mixture with emulsified (foamed) asphalt. Through a large number of tests, thepaper proposed relatively reasonable strain controlled level for cold recycling mixture,namely300με、250με、200με、150με。Tests showed that the strain level, RAP content, asphaltcharacteristics all affected the fatigue life of cold recycling mixture and strain level is themost significant factor. Used stiffness modulus and loading number estimation method to determine fatigue life of cold recycling mixture at low strain level. Fit four strainlevels—loading numbers to fatigue equation of emulsified(foamed) asphalt cold recyclingmixture with80%and100%RAP and proposed controlled strain index for different trafficrank. Referenced loading numbers of foreign long-life pavement and obtained cold recyclingmixtures fatigue limit strain100με by calculating.Referencing new pavement design method in our country, using design parameters ofcold recycling mixture obtained from the experiments, the paper calculated and optimized thepavement structure for different traffic and earth subgrade classification and thenrecommended typical structure of new second-class highway containing cold recycling layerfor Beijing area. Referencing foreign flexible pavement design idea, utilizing designparameters and the control indicators obtained from the experiments, the paper optimized thepavement structure undering traffic classification and old pavement strength grading and thenrecommended typical structure of maintenance pavement which contains cold recycling layerand draft nomogram for it. The paper has important guiding significance and works value forthe design of pavement structure containing recycling layer for Beijing area.