THz Cement Hydration Kinetics: Tracking C3S with Terahertz Spectroscopy
THz cement hydration analysis gives researchers something conventional techniques cannot: a way to track crystalline changes in real time as C3S converts to calcium silicate hydrate (C–S–H).
This peer-reviewed study from the Teralumen and CSIR-CEERI team, published in the Journal of Infrared, Millimeter, and Terahertz Waves (2018), compares THz spectroscopy of cement and tricalcium silicate (C3S) over 28 days. Furthermore, DFT simulations confirm the exact origin of each THz resonance observed during hydration.
Why THz Cement Hydration Tracking Outperforms Conventional Methods
XRD cannot resolve C–S–H — it is poorly crystalline. MIR spectroscopy is bond-specific and struggles to distinguish C3S from C–S–H, because both share overlapping resonances. By contrast, THz spectroscopy is sensitive to bulk crystalline arrangements. Therefore, it detects the structural shift from C3S to C–S–H polymorphs directly.
What the Research Found
- 520 cm⁻¹ resonance drops: This peak — due to SiO₄ tetrahedra bending in C3S — decreases significantly as C3S converts to C–S–H. It is the clearest THz marker of hydration progress.
- 450 cm⁻¹ stays constant: DFT simulations explain why: the same frequency range covers both C3S vibrations and C–S–H chain deformations. As a result, intensity stays stable even as the material transforms.
- Peak shifts confirm C–S–H formation: The 453 cm⁻¹ resonance shifts to higher wavenumbers in the first 24 hours. This shift directly confirms silicate polymerisation — the mechanism that builds concrete strength.
- C3S drives early strength: The same resonance trends appear in both cement and pure C3S samples. Therefore, C3S is confirmed as the primary driver of early-stage cement hydration and strength development.
- DFT simulations validated: CASTEP simulations of C3S, tobermorite 9, tobermorite 14, jennite, and portlandite matched the experimental THz spectra closely — confirming the origin of each resonance region.
Relevance to TeraXplor
This research forms part of the scientific foundation of TeraXplor’s material characterisation capability. In addition, it connects directly to Teralumen’s nanosilica hydration study — where THz spectroscopy tracked how nanosilica accelerates C–S–H formation in β-C2S over 100 days.
Full THz spectra, DFT simulation data, 28-day hydration tracking, and comparative cement vs C3S analysis are in the published paper: Journal of Infrared, Millimeter, and Terahertz Waves, 2018.