Asphalt Mixture Low-temperature Cracking And Relaxation Characteristic Research

It is universal all over the world that in the area where temperature drops suddenly or varies greatly, cracks may occur in asphalt pavement under the effect of temperature stress, which is recognized as one of major damage modes of asphalt pavement and seriously imperils highway service duration and quality. Based on above facts, scholars in different countries carried out plenty of research on theory and experiment.In order to evaluate the low-temperature performance of asphalt mixture and lucubrate low-temperature cracking mechanism, beam bending test, TSRST test, contraction coefficient test and direct tensile-relaxation test are adopted to research six typical asphalt mixtures in this article. In the process of research, these following works were mainly carried out:First of all, Combined System for Testing Low-Temperature Performance of Asphalt Mixture is developed to carry out TSRST test, contraction coefficient test and direct tensile-relaxation test. By optimizing test rack and monitor-control program, this system could conveniently conduct above tests, and furthermore, the direct tensile failure test also can be processed. It has been proved that the system developed presented the advantage of high accuracy, good reproducibility and high value of practical application via a lot of tests and application of material selection in Chang An Street Pavement Rehabilitation Project. Secondly, it has been discovered that three evaluating indexes bending strength, tensile strain and bending strain-energy obtained by beam bending test to evaluate the six different asphalt mixtures indicated inconsistent results; and furthermore, through variance analysis and principal component analysis of the four evaluating indexes obtained by TSRST test, and considering variability and physical significance of the indexes, the freezing temperature is selected as the evaluating index of low temperature anti-crack property of asphalt mixtures.Thirdly, through contraction coefficient test for six mixtures, we found that the diatomite modified asphalt mixture presented the property of less shrink; taking the grey relational analysis on the results of beam bending test, TSRST test and contraction coefficient test, we could also get an conclusion that there is the maximal relevance between the freezing temperature and curvature strain energy of asphalt mixture.Fourthly, through direct tensile-relaxation test, we got relaxation time and relaxation modulus of the six selected mixtures at different temperatures; and based on Time-Temperature Equivalent Principle and formula of Arrhenius, relaxation modulus master curve and master curve family of asphalt mixtures qre gotten; meanwhile, by fitting different viscoelastic models, eight-units Maxwell model is adopt as the constitutive model of mixtures, and then viscoelastic parameters of the mixtures are gotten at -10℃by nonlinear fitting.At last, by analyzing relaxation modulus master curve family of asphalt mixtures, it has been discovered that at different temperatures, the relaxation capability of the same mixture presented the same changing trend as time went on, except for some difference in capability. The lower the temperature was, the changing rate of relaxation modulus master curve would be smaller.