Mesoscopic pore characteristics analysis of aged bridge concrete based on X-ray computed tomography

The characteristics of mesoscopic pores in concrete bridges have significant influence on structural mechanical properties. In this study, 18 core specimens, taken from three decommissioned concrete bridges serving for about 25 years, were investigated using X-ray computed tomography (X-ray CT). After segmentation and 3D reconstruction with CT scanning images, the spatial characteristics for the porosity, volume, and shape of the concrete mesoscopic pores were analysed. The mesoscopic porosity decreases with the increase of concrete strength. The logarithm of the pore volume obeyed the Gumbel extreme value distribution, whose location and scale parameters had obvious bilinear degradation with depth. Ellipsoidal approximation was employed to precisely characterise the individual pore structure, and the Gaussian copula function could describe the joint distribution among the pore shape parameters. It was found that correlation coefficients of ellipsoidal shape parameters remained stable with depth. The proposed model quantitatively describes the mesoscopic pores in decommissioned concrete bridges and can shed certain light on concrete pore simulation.