Abstract
In this study, water permeation through cementitious materials was observed using magnetic resonance imaging (MRI). The influence of cement type on the magnetic resonance signal was studied subsequent to determining the parameters required for imaging. Consequently, adequate imaging of water permeating through hardened cement paste (HCP) made with white Portland cement was achieved, while water permeation through ordinary Portland cement-based HCP yielded poor signal. HCPs maintained at various levels of relative humidity (RH) were observed, and the signal was detected only from those maintained at an RH of higher than 85%. The water permeation depths in HCP were observed by using MRI, and the measured depths were compared to those measured via a spraying water detector on the split surface of the specimens. As a result, good agreement was confirmed between the two methods. Additionally, MRI was applied to concrete specimens; although it was found that water was not detected when a lightweight aggregate was used, water permeation through concrete with limestone aggregate was detectable via MRI. MRI will help in understanding how water permeation causes and accelerates concrete deteriorations such as rebar corrosion and freezing and thawing.
Highlights
Water is known to yield deleterious effects on concrete structures
magnetic resonance imaging (MRI) was applied to concrete specimens; it was found that water was not detected when a lightweight aggregate was used, water permeation through concrete with limestone aggregate was detectable via MRI
Non-destructive imaging of water in cementitious material was performed by implementing MRI; the following results were obtained according to the conditions and parameters used in this study. - T1 and T2∗, which yielded the relaxation curves for the signal acquired from
Summary
Water is known to yield deleterious effects on concrete structures. To observe the depth of water permeation through concrete, the concrete specimen can be split to measure the depth of the surface colour changes [1] [2]. 80% of the split surface area is aggregate, and the colour change due to permeated water is generally only visible in the cement paste. Some researchers have cut concrete specimens and dried them to evaluate mass changes due to water transfer, and to determine the moisture distribution [3]. Humidity sensors can be used to measure the moisture distribution [4] or water penetration depth in concrete [5]. The above methods only yield one- to two-dimensional information
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