Pore Structure Analysis of Mortar under Freeze-Thaw Cycles Using X-Ray Computed Tomography
Katsufumi HASHIMOTO, Hiroshi YOKOTA, Takafumi SUGIYAMA@and Takasumi KIKKAWA
Abstract:Frost damage due to freeze thaw action of pore water in concrete is an important issue on durability of concrete structures in cold regions. It is generally known that different temperature histories in freeze-thaw cycles affect scaling of concrete, in which the pore structure might be changed due to propagation of micro cracks. In previous research, 3D images from X-ray computed tomography have been used to analyze the pore structure of concrete. This study aimed to evaluate the pore structure of mortar under freeze-thaw cycles with different temperature histories by using X-ray computed tomography. As the results, 1) the temperature histories gave different progress of residual strain and void distributions, in which decrease of toutuosity and spacing factor were shown with more residual strain due to frost damage; 2) propagation of micro cracks due to frost damage probably increases spacing factors and tortuosity calculated from information obtained in analysis using X-ray computed tomography; and 3) tortuosity and spacing factor linearly correlated with diffusion coefficient although void ratio did not correlated with diffusion coefficient. Thus, this study showed that pore connectivity informed from tortuosity and spacing factor evaluated by X-ray computed tomography, in addition to pore structural indicators such as total pore volume, were reasonably discussed with progress of frost damage and alteration of diffusion coefficient. Key Words:Freeze-thaw cycles, Pore structure, X-ray CT, Tortuosity, Air-void spacing factor, Diffusion coefficient