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Study On The Low Temperature And Fatigue Performance Of Waste Tire Rubber Modified Asphalt Mixture

Posted on:2013-04-16Degree:MasterType:Thesis
Country:ChinaCandidate:L LiFull Text:PDF
GTID:2232330392458811Subject:Road and Railway Engineering
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In recent years, the world’s auto mobile industry has developed at a faster rate with thewell developed economy, resulting in high amounts of scrap tires every year. In general,mountains of scrap tires not only caused a serious environmental problem but also be a wasteof resources. However, previous studies on this issue have indicated that the crumb rubberpowders process from scrap tires can be an economic and effective asphalt binder modifierthat has greatly enhanced asphalt pavement performance.In this paper, the crumb rubber modifier (CRM) binder was produced by high-speedshear apparatus. In general, there are many factors in influencing CRM binders such asasphalt type, the crumb rubber concentration and the crumb rubber particle size. Therefore,the indexes such as needle penetration, softening point, ductility at5oC, elastic recovery andthe viscosity by rotational viscometer was employed for CRM binders. It was identified andverified by some tests in the lab that the usage of crumb rubber in virgin asphalt can improveresistance to rutting at high-temperatures, reduce fatigue property at low temperatures andtemperature susceptibility, improve the binder’s restore elasticity ability. Moreover, therubberized asphalt mixtures were produced according the Superpave mixing design. Theoptimal amounts of asphalt for AR-16and AC-16were determined by validating thecompaction and moisture susceptibility of the mixture under the most effective compactiontimes, respectively, absolutely the test results should be satisfied with the specification.The theory of J-integral in fracture mechanics was applied in this paper to study theproperty of rubberized asphalt mixture at low temperature. The fracture toughness wasemployed as an evaluation indicator for low temperature crack resistance of the mixture insemi-circular bending (SCB) test. In addition, the effects of graduation, amounts of asphalt,temperature, crumb rubber concentration and degree of fineness on rubberized asphaltmixture’s low temperature crack resistance was studied in this test. The test results indicatedthat the crack resistance of gap grading AR-16was much better than that of continuousgrading AC-16at low temperature, the rubberized asphalt mixture with20%crumb rubberconcentration had the best low temperature crack resistance under the optimal amounts of asphalt when the test temperature was0oC, and the smaller the grain size of crumb rubberpowder was, the better low temperature crackIn order to study the fatigue cracking of rubberized asphalt mixtures, the length ofdynamical crack propagation was obtain by image processing. Moreover, the correlativity offatigue frequency and the length of dynamical crack propagation was fitted by the secondexponential growth function..In addition, the factors included the grading type, asphaltcontent, temperature, stress ratio, load frequency, crumb rubber concentration and degree offineness. It was indicated that the fatigue life of gap grading mixture was much longer thanthat of continuous grading mixture, and the rate for crack propagation was much slower.When the loading was smaller, load frequency was lager and grain size of crumb rubberpowder was much smaller, the fatigue life of rubberized asphalt mixture with the optimalamounts of asphalt was longer, and rate for crack propagation was much smaller. It was alsofound that when the crumb rubber concentration was20%, the test result was the best.
Keywords/Search Tags:waste rubber powder, asphalt rubber, rubber as phalt mixture, the Semi-Circular bending test, J-integral criterion, fracture toughness
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