3D MULTIPLE CRACK SYSTEM EXTRACTION AND ANALYSIS USING MOTION-BASED IMAGE PROCESSING TECHNI.pdf

3D MULTIPLE CRACK SYSTEM: EXTRACTION AND ANALYSIS USING MOTION-BASED IMAGE PROCESSING TECHNIQUE T. Zhang 1 , E. Nagy 2 (Member, ASCE), E. Landis 3 (Member, ASCE), and G. Nagy 4 ABSTRACT We present a motion-based method to extract the multiple 3D crack surfaces from a sequence of 3D X-ray microtomographic mortar images. We verify the correctness and accuracy of results by ground truth obtained with simulated cracks in real specimens. We provide several three-dimensional measures of crack surface, including the number of cracks, surface area, volume, tortuosity, and permeability. Keywords: X-ray microtomography, image processing, concrete fracture. INTRODUCTION We examine the crack surfaces of concrete fracture by image processing. Although it is known that microstructural processes ultimately govern the fracture behavior of concrete, they have been ignored because “understanding of this problem is particularly weak” (Baz?ant 1995). Most previous research was conducted in 2D by analyzing the jagged contours of cracks. The results indicate that two-dimensional models are not effective in investigating concrete, which exhibits complex 3D fracture surfaces. X-ray microtomography produces a three-dimensional representation of the internal struc- tures of a concrete specimen at an unprecedented resolution (Landis et al. 1999). By applying increasing compressive loads to a specimen, this technique generates multiple volumetric im- ages that capture the fracture evolution. We acquire, from these images, the crack surfaces and provide some 3D measurements for characterizing the fracture process. In the following, we first explain this method. We evaluate the method and describe the types of measurements. We then present the results on two sequences of concrete images at the 6-μm resolution. We conclude our paper by summarizing our findings. MOTION-BASED METHOD TO RECOVER CRACK SURFACES This method recovers the crack surfaces in three steps. (a) Preprocessing locates the con-