Unilateral low-field magnetic resonance measurements of carbonation depth in unsaturated and saturated Portland cement mortars

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Abstract

Unilateral Nuclear Magnetic Resonance is used to characterize the carbonation depth in 0.60 w/c ratio unsaturated/saturated Portland cement mortars. A three-magnet array combined with a surface elliptical coil was utilized to obtain the Nuclear Magnetic Resonance signal at different positions along mortar samples. The T2 lifetime and signal intensity behaviors in the carbonated and non-carbonated zones were analyzed. Scanning Electron Microscopy images were used to identify the macro-porosity and micro-cracking in the samples. Results confirmed that the crossover point between profiles of T2 lifetime and signal intensity agree with the carbonation depth obtained by the phenolphthalein test. The carbonation depth at the position where the T2 lifetime begins to behave nearly constant is about 1.44 times the depth indicated by the phenolphthalein test. The spatial resolution was improved four times in comparison with previous research. Scanning Electron Microscopy images analysis confirmed a significant decrease in local porosity and crack area in the carbonated zone.

Original languageEnglish
Article number106237
JournalCement and Concrete Research
Volume138
DOIs
StatePublished - Dec 2020

Keywords

  • Carbonation depth
  • Mortar
  • Pore size distribution
  • Signal intensity
  • T lifetime
  • Unilateral NMR

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