46 / 2022-03-28 15:50:52

Porosity estimation and component change analysis of leaching deteriorated hardened cement paste with non-destructive integrated CT-XRD method

non-destructive integrated CT-XRD method,leaching,porosity

Calcium leaching process is caused by dissolution of soluble components in hardened cement paste and decalcification of C-S-H. This effect should be particularly considered in concrete structures contacting underground water for long periods of time such as radioactive waste storage and immobilization facility. Leaching process increases porosity of cement paste and also leads to change in component of hydration products beginning from the surface of cementitious material. Using equipment of non-destructive integrated CT-XRD method in SPring-8 facility in Hyogo, Japan, in-situ information of leaching deteriorated hardened cement paste is obtained by employing computed tomography and in-situ X-ray diffraction technique. CT images for the samples with different leaching period (30 days and 200 days) and temperature (20℃ and 80℃) are presented in this paper.  Porosity of leaching and un-leaching area of sample cross section is estimated with a newly proposed method which divide cement paste into pore phase and solid phase based on LAC (Linear Attenuation Coefficients) data for each voxel. The proposed analytical results show that leaching process is identified by CT-XRD method in the porosity evolution and the influence of temperature on leaching behavior.