Research on Modification of Volume Parameter Test Method and Influence of RAP Characteristics on Performance of Cold Recycled Mixture
In order to better control the performance of cold recycled mixture,the test methods of bulk specific gravity,theoretical maximum relative density and optimal moisture content of cold recycled mixture were modified.Simultaneously,the characteristics of RAP,including the content of old asphalt,penetration index,passing rate of 4.75 mm sieve and gradation change rate after extraction,were analyzed.The influence of RAP characteristics on bending tensile strength,water stability,high-temperature and low-temperature performance of emulsified asphalt cold recycled mixture was studied.The results showed that:1)The optimum moisture content of cold recycled mixture should be determined by the compaction work matching with the molding of the specimen,among the methods of measuring bulk specific gravity,the results of surface dry method are larger and more stable than that of wax sealing method,and the results of Corelock method are relatively true,considering the stability and accuracy of laboratory test results and economy,surface dry method is recommended;2)The modified theoretical maximum relative density test method can reduce the systematic error caused by vacuum test method;3)The smaller the content of old asphalt and the smaller the change rate of gradation,the lower the voids and the better the water stability of cold recycled mixture;4)The greater the penetration of old asphalt,the greater the fracture work and low-temperature splitting strength(-10℃,-25℃);5)The greater the penetration,the higher the passing rate of 4.75 mm sieve after extraction,and the worse the high-temperature performance of cold recycled mixture.
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