Investigation of self-sealing in high-strength and ultra-low-permeability concrete in water using micro-focus X-ray CT

Abstract

High-strength and ultra-low-permeability concrete (HSULPC) is thought to be useful as a radioactive waste package. Thus, a high confining ability is desirable.For cementitious materials, sealing of cracks may occur in water due to the precipitation of calcium compounds. This can affect the confining ability. In this study, the sealing of a crack in HSULPC in water was investigated using microfocus X-ray computed tomography (CT). The sealing by precipitation occurred only around the end of the specimen. Sealed regions of the crack were identified using three-dimensional image registration and CT image subtraction of images obtained for the specimen before and after it was immersed in water to evaluate temporal changes of the sealing deposits in the crack. The sealing deposits increased as the HSULPC specimen was kept in water longer. It was concluded that cracks in HSULPC in water are sealed by precipitation.

Early-Age Self-Healing of Cementitious Materials Containing Ground Granulated Blast-Furnace Slag under Water Curing

“…For the control mortar however, they are concentrated close to the top surface. This observation is in agreement with (Fukuda et al 2012), where the healing products distribution is important close to the top surface of a high-strength and ultra-low-permeability concrete specimen cured under seawater.…”

“…X-ray tomography is often used to produce 3D images of cementitious materials with or without mechanical loadings, to capture damage and strain localization. Few experimental results exist however related to self-healing (Van Tittelboom et al 2011;Henry et al 2013;Fan et al 2013;Fukuda et al 2012). Van Tittelboom et al (2011) adopted this technique to visually observe the crack and healing agent (polyurethane) distribution.…”

“…Their samples were characterized by a low water-cement ratio (≤ 0.3), a parameter favorable to healing by the ongoing hydration due to the presence of numerous anhydrous cement particles. Their studies differ by the adopted method to crack the specimen and the curing type after cracking: heating and water curing (Henry et al 2013); bending test and wet-dry cycles curing (Fan et al 2013); splitting test and sea water curing (Fukuda et al 2012).…”

“…Van Tittelboom et al (2011) adopted this technique to visually observe the crack and healing agent (polyurethane) distribution. Henry et al (2013), Fan et al (2013), Fukuda et al (2012) performed calculations using image analysis techniques to determine the crack width before and after the healing process in specific areas of the cracked cementitious materials. Their samples were characterized by a low water-cement ratio (≤ 0.3), a parameter favorable to healing by the ongoing hydration due to the presence of numerous anhydrous cement particles.…”

Control of the Polymorphism of Calcium Carbonate Produced by Self-Healing in the Cracked Part of Cementitious Materials

“…Researchers have also explored various approaches to promote self-healing, such as the use of bacteria, crystalline admixtures, and superabsorbent polymers [13][14][15][16][17][18][19][20][21]. Choi et al reported that a large amount of CaCO 3 precipitate was produced in the surface layer and inside microcracks because the self-healing of cement-based composite materials generated carbon dioxide gas in micrometer-sized ultrafine bubbles, which flowed into microcracks under a continuous water supply [1,22,23].…”