Study On The Fatigue Properties Of Asphalt Mixture Coupling With Tension And Compression Loads

As one of the main forms of asphalt pavement damage, the fatigue failure of asphaltpavement has been the focus of road researchers for decades. Reference to existing asphaltpavement design method all over the world, the tensile stress or tensile strain on the bottom ofthe asphalt surface are used to control and assess fatigue life of asphalt pavement. In thespecifications for design of highway asphalt pavement of our country, flexural tensile stress inthe bottom of the asphalt layer is used to control the fatigue cracking in the structural layers.But in fact, the stress-strain response at the bottom of the asphalt layer is in a tension andcompression alternating state under the vehicle loads. It has not only tensile strain but alsocompressive strain. Ignored the effect of the compressive stress, the existing research onasphalt mixture fatigue performance only study asphalt mixture’s fatigue performance underthe action of the tensile-tensile stress. After the experiments we got the prediction model ofthe asphalt mixture fatigue life, then it can be used to estimate the life of the actual asphaltpavement, guide the road maintenance, made anti-fatigue design and so on. In order tounderstand the fatigue performance of Asphalt pavement in the actual vehicle load, the authorstudied the properties of asphalt mixture fatigue under the condition of considering thetension and compression loads in this paper.Firstly, the indoor four-point bending beam testing method, which controlled by themode of stress was made. Three different types of asphalt concrete mixture AC-25, AC-20,AC-16were selected to make beam specimens, because they are so commonly used in asphaltconcrete road constructions. By using the fatigue testing machine MTS-810which made inUSA and the load-holding device which designed by ourselves, we test the fatigueperformance of beam specimens indoor.Secondly, as stress amplitude was selected the parameters, the test results were analyzed.Fatigue life prediction equations of the three asphalt concretes are established when they arein different stress ratios. The impacts of the stress ratio, test temperature and loadingfrequency on fatigue life of asphalt mixture are analyzed, and also the three kinds of asphaltmixtures’ fatigue performance are compared. In this paper, we evenly study the fatigue damage behavior of asphalt mixtures coupling with the tension and compression loads.Finally, the flexural stiffness modulus of asphalt mixtures parameter was defined,evolution regulation of asphalt mixture in the process of fatigue failure damage was studied.The fatigue damage evolution equation which considered the stress ratio, stress level wasestablished in this paper.