Studying On The Optimal Basic Test Parameters For Reflective Cracking Test Of Asphalt Mixture

In recently, in china, the highway construction is in the rapid development. However, he early destruction caused by h pavement cracking has become a universal problem. So the damage after the crack is coming, on the one hand, water intrusion from the cracks and the base layer even embankment become soften, resulting in the fall of the capacity of the road surface. The other hand, the nature instincts of mineral accelerate the stripping of asphalt from the stone surface and caused some other diseases. It will greatly educe the life of the pavement. Therefore, how to improve the durability of the road and nake faster and better development of China’s transportation, is a problem of road workers have been facing with.There is a wide range of types of the asphalt pavement cracks, and the causes are different. The cracks caused by the temperature and traffic loading, include temperature shrinkage cracks, Top-down cracks and reflective cracking. Top-down is that the cracks appeared in the road surface firstly, and then began to expand to the bottom of the road. Well-structured combination can effectively delay its emergence and expansion. And the temperature shrinkage cracks are common in the region of low-temperature and the seasons when the temperature difference is large. In the semi-rigid pavement structure, reflective cracking is the most common and difficult to resolve. One reason is that it is difficult to give a real and effective evaluation to the performance of the asphalt mixture.The cause of the reflective cracking is generally considered to be at a combined effect of the substantial and sustained cooling load of the car, the asphalt surface stress concentration at the seam end, and in the long-term effects of fatigue, cracks gradually extended to the road surface. The close relationship linked the production and development of reflective cracking, in addition to the load and temperature, but also with the structure of the road.Although the theoretical research about propagation of the reflection cracking is more and more in-depth, and the way to evaluate the asphalt mixture the, further research is needed. Overlay Tester is a newly and developed testing method used to evaluate the performance of anti-reflective cracking about the asphalt mixture. And then, it can effectively simulates the basic characteristics of the reflective cracking about the asphalt pavement, and evaluate asphalt mixture reflective cracking performance by applying cyclic loading and loading cycles. The parameters of the test include time, temperature, frequency, and stretching displacement. The parameters have not been effective analyzed and evaluated in current testing methods, just according to the experience of arbitrary to be selected. In order to improve the accuracy and validity of the testing method, the various testing parameters were compared with experimental testing and analyzed the impact of changes in various parameters of the testing results, to have an optimization about the basic parameters of the testing method in this paper. For optimization of the reflective cracking performance, the corresponding study results indicated the following:the optimum OT specimen thickness should be 40mm, and the optimum loading frequency should be 0.2 Hz. While the recommended TTI gap opening of 2mm was found to be satisfactory, the study results indicated that the maximum tensile displacement should be selected and calculated based on the interactive consideration of the Chinese local temperature conditions, pavement structure, and material type.