THz Fingerprints of Cement-Based Materials

Area of Science:

• Materials Science
• Solid-State Physics
• Chemistry

Background:

• Terahertz (THz) radiation is crucial for emerging technologies, yet its interaction with many materials, especially cement, is poorly understood.
• Cementitious materials are fundamental to global infrastructure, necessitating an understanding of their THz response for advanced applications.

Purpose of the Study:

• To identify and characterize the significant terahertz (THz) spectral fingerprints of cement-based materials.
• To investigate the dielectric response of calcium-silicate-hydrate (C-S-H) and sodium-aluminosilicate-hydrate (N-A-S-H) gels, key hydration products in Ordinary Portland Cement (OPC) and geopolymer (GEO) pastes, respectively.

Main Methods:

• Terahertz (THz) transmission experiments were conducted on Ordinary Portland Cement (OPC) and geopolymer (GEO) cement pastes.
• Atomistic simulations were employed to calculate the dielectric response of C-S-H and N-A-S-H gels.

Main Results:

• Both experimental and simulation results identified characteristic THz absorption peaks in OPC and GEO pastes around 0.6 THz, 1.05 THz, and 1.35 THz, attributed to water content dynamics.
• Additional peaks were observed near 1.95 THz and 2.75 THz, likely associated with the vibrational modes of the dried cementitious material skeleton.

Conclusions:

• The study establishes distinct THz spectral signatures for OPC and GEO cement pastes.
• Understanding these THz fingerprints provides a foundation for developing THz-based characterization and quality control methods for cementitious materials.