Microstructure and texture of cementitious porous materials

Area of Science:

• Materials Science
• Physical Chemistry
• Geotechnical Engineering

Background:

• Understanding the microstructure of cementitious materials is crucial for predicting their long-term performance and durability.
• Traditional methods for characterizing cement hydration often involve destructive techniques or require sample pre-treatment, which can alter the microstructure.
• Nuclear Magnetic Resonance (NMR) spectroscopy offers a non-invasive approach to probe material properties at a molecular level.

Purpose of the Study:

• To characterize the microstructure of various cementitious materials, including white and Portland cement pastes, mortars, and concretes.
• To investigate the dynamics of proton species, specific surface area, and pore size distribution during cement hydration using magnetic resonance.
• To establish a continuous, non-destructive monitoring method for cement hydration and microscale texture development.

Main Methods:

• Utilized various magnetic resonance techniques, focusing on proton nuclear magnetic spin-lattice relaxation measurements as a function of magnetic field strength (Larmor frequency).
• Applied standard proton nuclear spin relaxation and high-resolution Nuclear Magnetic Resonance (NMR).
• Performed measurements without requiring any drying temperature modification, enabling continuous monitoring.

Main Results:

• Demonstrated that magnetic resonance relaxation measurements provide reliable information on proton dynamics at the surface of calcium silicate hydrate (CSH).
• Successfully determined the specific surface area and pore size distribution throughout the progressive hydration of cement-based materials.
• Showcased the capability to continuously monitor the material during hydration due to the speed of the measurement.

Conclusions:

• Proton nuclear magnetic spin-lattice relaxation as a function of magnetic field strength is an effective method for characterizing cementitious material microstructure.
• The developed magnetic resonance technique allows for non-destructive, continuous monitoring of cement hydration and microstructural evolution.
• Coupling different NMR methods provides a comprehensive understanding of the development of microscale texture in cement-based materials.