Tomography-Based Investigation on the Carbonation Behavior through the Surface-Opening Cracks of Sliced Paste Specimen

Abstract

Understanding the cracking behavior during carbonation is of high importance, and the cracks can serve as a shortcut for CO2 diffusion, which can further accelerate the carbonation process itself. In this study, a sliced paste sample was taken for an accelerated carbonation test, and the cracking behavior, as well as its impact on carbonation, was investigated through a novel extended attenuation method based on X-ray (XRAM) which is performed primarily on computed tomography (CT). Surface-opening cracks at different carbonation ages were rendered, based on which a full view on the carbonation-cracking behavior was built. The results reveal that the crack paths can rapidly be occupied by CO2, and that leads to the generation of V-shaped carbonation cusps pervading the carbonation fronts. The V-shaped carbonation cusps were mostly generated at the early carbonation age (within 14 days), attesting to a less intact sample surface as compared to the inside area. Moreover, this study confirms that the carbonated area would split into two independent zones with variant carbonation degree due to the increased humidity level near the sample surface. The current work reveals the interconnection between carbonation and cracking, and the results can be used for the designing of cement-based materials with better carbonation and cracking resistance.

Effect of Carbonation on Microstructure Evolution of Alkali-Activated Slag Pastes

“…A new extended X-ray attenuation method (XRAM) was established by combining X-ray CT and attenuation coefficient method. This method can effectively make up for the resolution deficiency of CT, and can reveal the local porosity of alkali-activated concrete during carbonation [8] . On the premise that CT test parameters remain unchanged, the local porosity of the sample can be calculated according to Formula (1).…”

Use of Graphene Oxide to Improve the Durability and Mechanical Properties of Mortar Immersed in Flowing River for Three Years

“…To mitigate the deficiency, several researchers, including the authors here, attempted to propose novel methods which can enhance the precision level of CT [37,38]. One author recently developed a method, denoted as "dual-scan" method, and adopted an altered local attenuation coefficient during the dual CT scan, instead of local attenuation coefficient from a single CT scan to measure the local porosity of a scanned object [39]. Since water was used as the intrusion agent in dual CT scan, the covered range of pores could be even broader than mercury intrusion porosimetry (MIP) [40].…”