Inproceedings - Abstract Book Contribution

English

Liberto, Teresa 
Dziadkowiec, Joanna 
Valtiner, Markus 
Robisson, Agathe 

E207-01 - Forschungsbereich Baustofflehre und Werkstofftechnologie 

International Congress on Rheology (ICR 2023) Book of Abstracts 

4-Aug-2023

XIXth International Congress on Rheology (ICR 2023) 

29-Jul-2023 - 4-Aug-2023

Athens, Greece

1

SAOS (small oscillatory rheology); SFA (Surface force apparatus); C-S-H; early cement hydration

Extremely robust cohesion triggered by calcium silicate hydrate (C-S-H) precipitation during cement hardening makes concrete one of the most commonly used man-made materials. This abstract illustrates a study combining rheological and surface force measurements to seek further nanoscale understanding of the cohesive forces acting between hydrating model tricalcium silicate (C3S) surfaces. Time-resolved small oscillatory rheology measurements (SAOS) is used to characterize the early-stage evolution of the cohesive properties of a C3S paste and a C-S-H gel. SAOS revealed the reactive and viscoelastic nature of C3S pastes, in contrast with the non-reactive but still viscoelastic nature of the C-S-H gel, which proves a temporal variation in the cohesion during microstructural physico-chemical rearrangements in the C3S paste. Thin C3S films by plasma laser deposition (PLD) were prepared to be suitable for force measurements in the surface forces apparatus (SFA).We measured surface forces acting between two thin C3S films exposed to water and subsequent in-situ calcium silicate hydrate precipitation. SFA and SFA-coupled interferometric measurements resolved that C3S surface reprecipitation in water was associated with both the increasing film thickness and progressively stronger adhesion (pull-off force). The lasting adhesion developing between the growing surfaces depended on the applied load, pull-off rate, and time in contact. These properties indicated the viscoelastic character of the soft, gel-like reprecipitated layer, pointing to the formation of C-S-H. The evolution of cohesion of the C3S paste observed via SAOS can be attributed to the formation of hydrated calcium silicate surfaces that, as observed via SFA measurements, are responsible to sharp changes in the surface microstructure. In contact with water, the brittle and rough C3S surfaces with little contact area, weather into soft, gel-like C-S-H nanoparticles with a much larger surface area available for forming direct contacts between interacting surfaces.

Materials Characterization: 50%
Surfaces and Interfaces: 50%

1040 - Chemie: 35%
2011 - Bauingenieurwesen: 30%
1030 - Physik, Astronomie: 35%