Basic Characteristics Research On Coarse Aggregates Of Asphalt Mixture Based On X-ray CT

Superpave is an important research achievements of Strategic Highway Research Program. Compared with the traditional design method of Marshall, Superpave has made a great improvement in the design methods of asphalt. However, Superpave can't directly obtain the interior volume constitutions of asphalt, which prevents it from wide application. Moreover, the road surface which is designed based on the Superpave has exhibits early-stage damages of different degrees. In this respect, the traditional asphalt design methods and concept falls short of actual requirement and they need to be reformed.Scientists put more and more concern on how to directly measure the volume constitutions of asphalt mixture and take it as a major research direction. Under the background, scientists have introduced Digital Image Processing into the research field of civil engineering gradually. Because of its various merits, DIP has achieved fast development in the research field of civil engineering and generated new research directions with wide development perspectives.However, traditional two-dimensional imaging processing method has an obvious limitation, that is, being unable to completely reflect the actual structural information of three-dimensional space. In order to acquire the real image of interior constitution, we need to resort to technological aides like cutting the concrete specimen. However, the methods would cause damage to the original concrete specimen and it can't be acted upon with further test methods of basic mechanical properties.By obtaining the interior successive slice images of specimen, X-ray Computed Tomography reflects the real structural information of three-dimensional space of scanned specimen. The acquired digital image is real and accurate and its reconstruction accuracy is rather high, which exhibits great development potentials and application perspective. We are able to acquire the interior special constitution of asphalt mixture by adopting the technology, analyze the volume parameters and carry out virtual dynamic simulation experiment. In this respect, the technology has gradually become a research hotspot in the field of scientific research. To realize the computer-aided asphalt mixture design by making use of the technology is becoming a great and expectant objective.From the domestic and foreign successes by stages, we can find that the relative scientific research on the concrete by adopting X-ray CT technology has just been established and it is just stated in our country. Now we can't fully exert its merits in obtaining the three-dimensional structure information with high-accuracy. What's more, our work is not sufficient in borrowing the improved and developed knowledge of inter-disciplines and we haven't realized an effective inherit and innovation on the traditional dynamic theories. In order to realize the objective of computer aided asphalt mixture design, large quantity of fundamental research works are necessary.Based on the current research situation, the paper follows the research principles of“staging, emphasis and implementation in a planned way”. The paper takes the coarse aggregate whose volume occupies great proportion in the asphalt mixture as the research target. Started from the basic properties of coarse aggregate, the paper has integrated the latest research results of inter-disciplines and tried to solve problems relevant to the key technologies of CT in the applied industrial research while carrying out the research on the properties of coarse aggregate.The paper generalized the physical methods and technological measures in improving the quality of asphalt mixture's CT scanning image, optimizes the parameter setup in the process of scanning, analyzes the subjective and objective factors which interferes the imaging quality and raises preventive measures. Moreover, the paper tries to produce the calibrating apparatus and make evaluations on the reference material of test methods. The paper carries out application analysis on the mainstream and commercial image processing software and implements the elementary software design and the re-development works based on the Matlab and directed at the special requirement of asphalt mixture research.By borrowing the latest research achievement in the domains of digital image processing and the pattern recognition, the paper tries to realize the self-adaption classification of 2D slicing images and makes analysis on the extracted coarse aggregate. Moreover, the paper has established a brand new 3D matching method of coarse aggregate's successive slicing image sequence, based on which the paper determines what picture element of the coarse aggregate's component belong to. The paper has successfully turned the research on the property of coarse aggregate from the 2D platform to the 3D platform.By combining the digital image processing methods, the paper explored new approach in describing the 3D special relations of coarse aggregate and tried to establish a new quantified index in evaluating the contact degree of coarse aggregate's framework inside the asphalt mixtures.The paper makes rational mathematic description on the coarse aggregate's 2D and 3D outlines in the acquired slice images by CT scanning, based on which the paper makes improvement on the traditional experiment methods in evaluating the morphological properties of coarse aggregate. Meanwhile, the paper provided beneficial reference to the simplified description of coarse aggregate articles in the virtual dynamic experiments.