| In recent years,cold in-place recycling(CIR)technology using asphalt emulsion has begun to be used on a large scale in the lower layers and base layers of high-grade highways because of its 100% utilization of old materials,low-carbon environmental protection,a large number of indoor studies which were carried out,and construction technology of mature.However,the application and promotion in the middle surface layer of expressways were limited by the shortage of the design method and the performance of the material itself.Therefore,this paper starts from the research on the performance improvement of modified emulsified asphalt and the key factors of mix proportion design,compares the road performance of hot and cold mixtures,and finally based on the application of solid engineering,CIR technology is analyzed in applicability of the surface layer in the highway.Firstly,compared the preparation method of modified emulsified asphalt,and the preparation process of laboratory tests and engineering production was determined.By carrying out the conventional physical properties,rheological properties of Superpave system,the modified emulsified asphalt residues with different amounts of latex in the conventional physical properties,rheological properties,and microscopic morphological studies.Combined with evaluation index analysis,comprehensive consideration of economy and modification efficiency,to determine the best latex dosage.Secondly,through the gradation design of the emulsified asphalt cold recycled mixture(CEAM)and the research on the optimal moisture content,the milling speed of the cold recycling machinery during construction was determined,and the linear fitting equation of the optimal moisture content and temperature was established.Based on the analysis of compaction characteristics,the compaction times of indoor mixed test were determined,and the optimal spacing between the regeneration and paving units was obtained.compare different molding methods and curing temperatures,and provide a reference method for the construction of the construction quality inspection mixture.The mix design of the recycled mixture was carried out,and the optimal blending amount of the two cold recycled mixture materials was determined.Then,based on the comsol finite element software,the temperature field of Fenguan highspeed cold-recycled pavement structure was analyzed in winter and summer,and the test temperature of high-temperature creep and low-temperature fracture of the cold-recycled mixture closer to reality was determined.Multi-sequence repeated layered creep and fullthickness creep tests compare the high-temperature creep properties of four types of cold and hot mixtures and seven types of monolithic pavement structures.By means of semi-circular bending fracture test,the crack resistance performance of two kinds of CEAM under the condition of medium and low temperature is compared,and the fracture parameter variation rule under different loading rates is analyzed.Through the semicircular bending fatigue test,a fatigue equation based on stress ratio and stress amplitude was established,and the fatigue performance of four mixtures was evaluated from an energy perspective.Finally,through the Fenguan highway CIR project,the research results were applied to the solid project.The applicability of the technology to the middle surface layer of the highway was further verified through the pavement structure check calculation and performance tracking observation of the test section.Combined with the quantitative analysis of economic and environmental benefits,the capital cost and energy consumption of Fenguan Highway CIR Project were analyzed quantitatively.The research results of this paper have laid a solid foundation for the large-scale application of modified CIR technology in highway maintenance engineering and provided a new engineering practice case for the structural repair of highway asphalt pavement in China. |
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