Research On The Fatigue Failure Mechanism Of Asphalt Mixture Modified By Sulfur

The asphalt pavement has the advantages of comfortable driving, short construction period and without affecting the traffic. Asphalt pavement is widely used in high grade highway pavement, but asphalt pavement will be premature to rutting and fatigue cracks for the poor high temperature stability and anti-fatigue performance of common asphalt mixture. Fatigue failure is the main failure form of asphalt pavement, and it is also the origin of the basic theory and design of asphalt pavement structure. The fatigue damage of asphalt pavement mainly resulted from the increase of the driving load, the change of environmental factors and the variation of the meso structure of asphalt mixture. Therefore, improving the fatigue performance of asphalt pavement and prolonging the service life of pavement become a major research topic for asphalt pavement.The use of adding additives to the modified asphalt has a long history. In the middle of nineteenth Century, it was used to improve the performance of asphalt pavement by sulfuration. The quality of waxy asphalt and its high temperature stability of asphalt mixture can be improved by Sulfur modifying agent of Thiopave. Since the beginning of last century, some experimental studies on sulfur modified asphalt mixture was carried out by some developed countries of petroleum industry. However, since the last 1990s, with the low sulfur price and the price of asphalt is rising, the sulfur modified asphalt mixture has become one of the hot spots in the research of asphalt mixture abroad. Analysing from the current collection of the literature, domestic research on the road performance of sulfur modified asphalt mixture is not comprehensive and thorough. Domestic literature on sulfur modified asphalt mixture is very few, and most of them remain in laboratory tests and small-scale test road research. In Yunnan Province, only a First-Grade Highway in Getun of Honghe Prefecture and Meng-Xin Expressway have respectively paved Sulfur modified asphalt mixture pavement with 15.717 km and 2 km. On the outher hand, sulfur modifier material can instead of a part of the asphalt content. So, the main content of this paper is to study whether the fatigue performance of asphalt mixture is affected by the reduction of asphalt content. Firstly, In this paper, the road performance of the ordinary asphalt mixture and the different content of sulfur modified asphalt mixture was carried out based on the AC-13 gradation, including high temperature stability, low temperature crack resistance and fatigue property. Secondly, it is different from using low temperature bending test of asphalt mixture, the fatigue failure of asphalt mixture was researched. In this paper, the splitting fatigue test of asphalt mixture was carried out by using the self-made split loading test fixture. The fatigue damage of asphalt mixture was studied by the method of digital image correlation (DIC), Matlab software and concrete crack theory. The displacement field and strain field of the asphalt mixture during the fatigue loading are obtained. Through the DIC method, the image information is transformed into the deformation information which can represent the mechanical properties of the material, and the fatigue failure process of the asphalt mixture is analyzed.The results showed that:(1) Asphalt mixture modified by sulfur can effectively improve the asphalt mixture with road properties, improving the rutting resistance of the mixtures, anti-shear ability and anti-fatigue capability. (2) With the increase of the content of the modifier, the performance of the asphalt mixture and the splitting fatigue performance are improved gradually. In the total binder sail paving quality under the condition of 30%-40% percentage, the performance is better than the ordinary asphalt mixture increased more than 3 times. When the quality of cementing materials in the total of 35% thiopave, the performance of asphalt mixture can be improved obviously. But at 40%, the performance of the modified asphalt mixture is close to 30%. So the best quality of sulfur modified asphalt mixture is 35%. (3) Combined with DIC technology and Matlab programming to calculate the displacement field and strain field of asphalt mixture, the damage evolution law of asphalt mixture is analyzed. At the initial stage of damage, the damage degree of the test specimen is small and the distribution is not uniform. With the effect of repeated loading, the damage increases and tends to be concentrated, which leads to the formation of cracks and continues to expand, leading to the failure of the specimen. (4)The fatigue cracking process of asphalt mixture is explained by analyzing the deformation of specimen during fatigue test and the displacement field and strain field of the center region with the specimen during the loading process of digital image processing technology.In this paper, the performance of sulfur modified asphalt mixture shows that sulfur modified asphalt mixture has superior performance, which can be used in pavement to improve the service life of pavement. It was analyzed the deformation and crack of asphalt mixture by digital image correlation method and Matlab software. The test data of this paper can provide a reference for the analysis of the performance of the asphalt mixture in the future.