C-S-H Pore Size Characterization Via a Combined Nuclear Magnetic Resonance (NMR)-Scanning Electron Microscopy (SEM)...

Area of Science:

• Materials Science
• Geochemistry
• Analytical Chemistry

Background:

• Nuclear magnetic resonance (NMR) relaxometry is crucial for characterizing porous materials like hydrated cement.
• Accurate surface relaxivity calibration is essential for interpreting NMR data in cementitious systems.
• Existing calibration methods may not fully capture the complex pore structures in hydrated cement.

Purpose of the Study:

• To propose and validate a new method for calibrating NMR surface relaxivity in hydrated cement.
• To combine scanning electron microscopy (SEM) and proton time-domain NMR (¹H-TD-NMR) relaxometry for this calibration.
• To compare the proposed method with the conventional sequential drying technique.

Main Methods:

• Utilized 28-day hydrated tricalcium silicate (C₃S) samples.
• Acquired high-resolution SEM images of pore structures after argon broad ion beam sectioning.
• Performed ¹H-TD-NMR relaxometry to obtain T₂ relaxation times.
• Calculated surface relaxivity using the fast-exchange model of relaxation.

Main Results:

• The combined SEM-image analysis and ¹H-TD-NMR relaxometry provided pore surface and volume data.
• Surface relaxivity was successfully calculated using the fast-exchange model.
• The new method's results were compared against those obtained via sequential drying.

Conclusions:

• The proposed method offers a robust approach for NMR surface relaxivity calibration in hydrated cement.
• This technique enhances the characterization of interhydrate pore structures.
• The findings contribute to more accurate NMR-based analysis of cement hydration and microstructure.