| As a kind of macromolecule waste which is very difficult to degrade,waste tires is ground into crumb rubber and added to asphalt,which can not only improve the road performance and driving comfort,but also effectively solve the black pollution caused by the waste tires.However,the poor compatibility between rubber powder and asphalt leads to the segregation of modified asphalt during the storage process,which is also the main problem restricting the application and development of rubber asphalt.In view of the above problems,the surface of waste rubber powder was activated via chemical grafting method.The purpose was to improve the compatibility between the rubber particles and the asphalt and then improve the road performance of modified asphalt.There are a lot of unsaturated double bonds in the rubber molecular chain and acid groups in the asphalt,so based on the molecular design principle,the acrylamide with C=C bonds and basic amide groups was selected as the modifier to activate the rubber.The asphalt modified by grafting activated crumb rubber was prepared through the wet process,and its road performance,microstructure and aging performance were studied.The main research contents are as follows:(1)Modified asphalts with different content of graft activated crumb rubber were prepared.The conventional physical properties and rheological properties were tested to study the influence of rubber content on the properties of modified asphalt.The test results showed that the high and low temperature rheological properties were improved with the increase of rubber content.The ordinary crumb rubber modified asphalt was prepared as a reference sample under the same conditions to study the effect of grafting activated rubber.The results showed that the activation of crumb rubber endowed the modified asphalt better consistency and ductility,and improved the high and low temperature performance of modified asphalt.(2)The microstructure test was performed on the grafting activated crumb rubber and modified asphalt to establish the relationship between the microstructure and the macro performance.From the infrared spectrum and scanning electron microscopy of the activated rubber,it can be concluded that a chemical reaction occurred between acrylamide and the rubber particle.Hence,the grafting activation of crumb rubber belongs to chemical method.The surface of the activated rubber particle was rougher,the surface energy was greater,and the interaction with the asphalt was strengthened.(3)Modified asphalt was stored for different length of time at 163℃.The separation softening point difference and the rutting factor separation index were used to characterize the storage stability of modified asphalt.The results showed that the segregation softening point difference and the rutting factor separation index of the grafting activated crumb rubber modified asphalt were significantly lower than that of the ordinary crumb rubber modified asphalt at the same storage time.It indicated that the compatibility of the activated rubber and asphalt was improved.At the same time,it can be observed by fluorescence microscope that the activated crumb rubber was evenly dispersed in asphalt,and the degree of separation of crumb rubber was significantly reduced.(4)The RTFOT test and the PAV test were carried out on modified asphalt to simulate the aging phenomenon in actual use.The microstructure,physical properties and rheological properties were tested to study the influence of the activated rubber on the aging performance of the modified asphalt.The results showed that the aging resistance of the activated crumb rubber modified asphalt were significantly better than that of the matrix asphalt and the ordinary crumb rubber modified asphalt,which indicated that the activated rubber could reduce the aging degree of asphalt.The infrared spectrum showed that the chemical crosslinking between the activated rubber and the asphalt was maintained,which effectively alleviated the aging phenomenon of the modified asphalt. |
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