TU München Centre for Building Materials (cbm) Relevanz von Thixotropie und Strukturaufbau für die Verarbeitungseigenschaften von Beton Relevance of thixotropy and structural build-up for workability of concrete Dirk Lowke, Thomas Kränkel & Oliver Mazanec
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Relevance of thixotropy and structural build-up for ... TU München Centre for Building Materials (cbm) Relevanz von Thixotropie und Strukturaufbau für die Verarbeitungseigenschaften
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TU München
Centre for Building Materials (cbm)
Relevanz von Thixotropie und Strukturaufbau für die
Verarbeitungseigenschaften von Beton
Relevance of thixotropy and structural build-up for
workability of concrete
Dirk Lowke, Thomas Kränkel & Oliver Mazanec
t
Str
uctu
re (t,h)
Shear load Rest
Thixotropy [greek] property of certain two-component-systems, to fluidify under
mechanical load (stir, shake, ultra sonic) at constant water content. At rest, the
substance hardens again. - Herbert Freundlich (1880-1940)
Thixotropy
t
2
t
Str
uctu
re (t,h)
Shear load Rest
Thixotropy of cement-based suspensions
t
3
Microstructure in cement-based suspensions
Particle structure in a cement-
basied suspension.
Cryo-FIB-record
duration of hydratation: 24 min
Zingg [2008]
“Static” rheology
=
Structural strength
=
Number and strength
of particle contacts
4
t
Str
uctu
re (t,h)
Shear load
Rest t
Shear load
Microstructure in cement-based suspensions
Structural
break-down
5
τ0D
Microstructure in cement-based suspensions
Particle structure in a cement-
basied suspension.
Cryo-FIB-record
duration of hydratation: 24 min
Zingg [2008]
Dynamic
Rheology
=
Structural
break-down
6
τ0D
t
Str
uctu
re (t,h)
Rest t
Shear load
Microstructure in cement-based suspensions
Structural
build-up
7
τ0(t)
Structural build-up – Mechanisms and temporal progression COLLOIDAL SURFACE