Evaluation of Meso-damage Processes in Concrete by X-Ray CT Scanning Techniques Under Real-Time Uniaxial Compression Testing

Concrete damage characteristics were investigated by X-ray computed tomography (CT) under uniaxial compression, with medical X-ray CT and a loading device used to carry out real-time uniaxial compression scanning tests, obtaining two-dimensional CT images of crack generation, propagation, coalescence, and failure. Damage deterioration of internal structures under different loading conditions was analyzed by means of a digital image-processing technique, which allowed the recognition and extraction of meso cracks. Furthermore, the crack lengths were extracted and measured from CT images. Methods of divisional regions were applied to carry out the quantitative analysis of CT numbers in specific representative regions. The fractal dimensions (FDs) of crack propagation in CT images were estimated using the box-counting dimension, and the relationship between the strain, crack propagation, and FD examined. Complicated and disordered internal cracks were clearly observed with increased load. The results indicated that such CT tests were a promising means for identifying the evolution and propagation of internal cracks and for studying the mesoscopic damage fracture mechanism under uniaxial compression.