THz Cement Hydration Tracking: How Nanosilica Accelerates C–S–H Formation in β-C2S
RESEARCH • Journal of Infrared, Millimeter, and Terahertz Waves • 2019 • Teralumen Solutions / CSIR-CEERI, Chennai
THz cement hydration analysis is revealing insights that conventional techniques like XRD and NMR simply cannot provide — and this peer-reviewed study from the Teralumen / CSIR-CEERI team is a clear demonstration of why.
Published in the Journal of Infrared, Millimeter, and Terahertz Waves (2019), this research uses THz spectroscopy to track the hydration of β-dicalcium silicate (β-C2S) — the second most common constituent of Ordinary Portland Cement — over a 100-day period, with and without nanosilica incorporation.
Why THz Cement Hydration Research Matters
Cement production accounts for 5–7% of global CO₂ emissions. β-C2S forms at just 700°C — far lower than the 1250°C needed for C3S — making it a compelling lower-carbon cement constituent. The challenge: β-C2S hydrates slowly in the early stages, limiting early concrete strength.
Adding nanosilica (particle size ~80 nm) triggers pozzolanic reactions that accelerate hydration and promote early formation of calcium silicate hydrate (C–S–H) — the key product responsible for concrete strength. This study is the first long-term THz spectroscopy study of β-C2S hydration with nanosilica.
What the Research Found
- Accelerated hydration confirmed: Nanosilica-incorporated β-C2S samples showed significantly faster reduction in the 500–519 cm⁻¹ THz resonances — directly tracking consumption of β-C2S. At 5% nanosilica, reduction was faster than at 2%, and both exceeded the control sample.
- Early C–S–H formation detected: A resonance at 455 cm⁻¹, attributed to C–S–H formation, appeared by day 7 for the 5% nanosilica sample — versus day 15 for 2% nanosilica and after day 20 for the control. THz spectroscopy detected this earlier than conventional techniques.
- Structural ordering tracked: Sharpening of the 283 cm⁻¹ resonance during hydration indicates formation of more ordered C–S–H and Ca(OH)₂ structures — an effect more pronounced in nanosilica samples.
- Different polymerisation from C3S: Resonance shifts in β-C2S hydration differ from those seen in cement and C3S, suggesting a distinct degree of silicate polymerisation during C–S–H formation — a new finding enabled by THz spectroscopy.
- SEM confirms THz findings: Scanning electron microscopy showed fibre-like C–S–H morphologies appearing by day 35 for the 5% nanosilica sample, versus day 100 for the control — visually confirming accelerated hydration.
Why THz Spectroscopy Outperforms Conventional Methods Here
XRD struggles to track C–S–H because it is poorly crystalline — its peaks overlap with calcium carbonate and cannot be reliably quantified. NMR can monitor silicate chain polymerisation but is slow and costly. THz spectroscopy provides continuous, quantitative tracking of both reactant consumption and hydration product formation — across all stages of the 100-day study.
Broader Significance: Lower-Carbon Cement Engineering
This THz cement hydration study is a step toward engineering β-C2S-rich cement matrices with nanomaterial accelerators — a path to reducing CO₂ emissions in cement manufacturing without sacrificing early strength. The findings also open the door to using THz spectroscopy as an in-process quality tool for cement production.
Full methodology, DFT simulations, THz spectra, SEM results, and 100-day hydration data are in the published paper: Journal of Infrared, Millimeter, and Terahertz Waves, 2019.
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