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Detecting Early-Stage Cohesion Due to Calcium Silicate Hydration with Rheology and Surface Force Apparatus
Teresa Liberto1, Andreas Nenning2, Maurizio Bellotto3
1Institute of Materials Technology, Building Physics and Construction Ecology, Faculty of Civil Engineering, Vienna University of Technology, 1040 Vienna, Austria.
Langmuir : the ACS Journal of Surfaces and Colloids
|November 25, 2022
Summary
This study reveals how calcium silicate hydrate (C-S-H) forms and strengthens cement at the nanoscale. Researchers used rheology and surface force measurements to understand early cohesive forces in tricalcium silicate (C3S) pastes.
Area of Science:
- Materials Science
- Nanotechnology
- Physical Chemistry
Background:
- Concrete's widespread use relies on the robust cohesion from calcium silicate hydrate (C-S-H) precipitation during cement hardening.
- Understanding the nanoscale origins of these cohesive forces is crucial for advancing cementitious material science.
- Early-stage interactions between hydrating tricalcium silicate (C3S) surfaces govern the material's long-term properties.
Purpose of the Study:
- To investigate the nanoscale cohesive forces between hydrating model tricalcium silicate (C3S) surfaces.
- To elucidate the role of calcium silicate hydrate (C-S-H) precipitation in early-stage cement cohesion.
- To combine rheological and surface force measurements for a comprehensive understanding.
Main Methods:
- Time-resolved small oscillatory rheology measurements (SAOS) were used to analyze the cohesive properties of C3S pastes and C-S-H gels.
- Thin films of C3S were prepared using plasma laser deposition (PLD) for surface force measurements.
- Surface force apparatus (SFA) and interferometric measurements were employed to quantify forces between C3S films in water.
Main Results:
- SAOS revealed C3S pastes as reactive and viscoelastic, while C-S-H gels were nonreactive but viscoelastic, indicating temporal cohesion changes.
- SFA measurements showed increasing film thickness and adhesion (pull-off force) during C3S reprecipitation in water.
- Adhesion depended on load, pull-off rate, and contact time, confirming the viscoelastic nature of the soft, gel-like C-S-H layer.
Conclusions:
- Hydrated calcium silicate surfaces exhibit strong cohesive properties attributed to microstructural changes.
- In water, brittle C3S surfaces transform into soft, gel-like C-S-H nanoparticles, significantly increasing contact area and cohesion.
- This study provides nanoscale insights into the fundamental mechanisms driving cement cohesion.
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