Research On The Modification Mechanism And Performance Of Stabilized Asphalt Rubber

Both rubber and asphalt are polymer organic materials.The two are affinitive in chemical properties.Compared with the matrix asphalt,asphalt rubber is better in High temperature stability,low temperature crack resistance and fatigue resistance.And stabilized asphalt rubber improves its storage stability on the basis of traditional asphalt rubber.This thesis chooses four kinds of asphalt including matrix asphalt,SBS modified asphalt,stabilized asphalt rubber and crumb rubber modified asphalt.The microstructure and the performance of asphalt binder and mixture of the four kinds of asphalt are investigated experimentally.The main work of the paper includes the following aspects:(1)Firstly,the modification mechanism of rubber asphalt was explored by means of micro-experiment.The most commonly used matrix asphalt and SB'S modified asphalt were taken as comparison.The result of infrared spectroscopy showed that the rubber powder and asphalt were mainly physically blended,accompanied by a weak chemical reaction.Furthermore,stabilized asphalt rubber and crumb rubber modified asphalt were of no significant difference in chemical composition.The result of Scanning electron microscopy showed the present state of rubber particles in asphalt rubber.It shows that the stabilized asphalt rubber reacts more violently than crumb rubber modified asphalt.The temperature stability showed by the differential thermal analysis:SBS modified asphalt>stabilized asphalt rubber>crumb rubber modified asphalt>matrix asphalt.The peak of Gel Permeation Chromatography was separated to get the relative content of large,medium and small molecules.It shows that there are more large molecules and less small molecules in asphalt rubber than those in matrix asphalt.(2)On the basis of testing the general performance indicators of the four kinds of asphalt,their high temperature rheological properties were evaluated by rotational viscosity test and temperature scanning in DSR.The two get a unified conclusion:stabilized asphalt rubber>crumb rubber modified asphalt>SBS modified asphalt>matrix asphalt.The result of MSCR in 64? showed that stabilized asphalt rubber is more suitable for heavy traffic compared to rubber modified asphalt.The fatigue properties of the four kinds of asphalt evaluated by time scanning in DSR showed that in the temperature 0?,5? and 15?,stabilized asphalt rubber was the best,and crumb rubber modified asphalt got the second place,and both of them were better than SBS modified asphalt and matrix asphalt.(3)Using the same SMA-13 gradation curve,three different kinds of stabilized asphalt rubber mixtures were designed by Marshall volume design method.The target porosity was 4%.The best asphalt-aggregate ratio were 6.0%(Nanjing),6.3%(Zhenjiang),6.2%(Beijing),respectively.Dynamic modulus test were conducted at different temperatures and at different frequencies.Dynamic modulus master curve was got by time-temperature equivalent principle.And the curve was then fitted by Sigmoidal function.The high temperature stability of asphalt mixture can be characterized by the dynamic modulus at the frequency of 10-4Hz-10-2Hz.The result showed that stabilized asphalt rubber mixture from Nanjing got the best high temperature stability.The high temperature stability of asphalt mixture characterized by the static creep test in 60 ? got the same result with the dynamic modulus test.The fatigue properties of the three kinds of stabilized asphalt rubber mixtures were evaluated by the four point bending test at 15?.The results showed,fatigue property:stabilized asphalt rubber mixture(Nanjing)>stabilized asphalt rubber mixture(Zhenjiang)>stabilized asphalt rubber mixture(Beijing).But the sensitivity of fatigue life to strain change of the three kinds of stabilized asphalt rubber mixtures are basically the same.The stabilized asphalt rubber from Nanjing is preferable according to the above results.Mixture ratio design was carried out according to the three gradation types AC-13,SUP-13,EME-20.The best asphalt-aggregate ratio were 5.6%,4.7%,5.4%,respectively.The high temperature stability,water stability and low temperature crack resistance of the three mixtures were evaluated by laboratory tests.The results show that the stabilized asphalt rubber has good applicability in three gradation types.