Modeling the Rheological Properties of Concrete

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Modeling the Rheological Properties of Concrete

• Nicos Martys
• James Sims

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Prediction

• Input
• Cement Paste
• Viscosity
• Yield stress
• Aggregates
• grading
• concentration

• Output
• Mortar/concrete
• Viscosity
• Yield stress

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Viscosity vs. Solid Concentration
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What is Concrete?

• Aggregates 1- 20 mm
• Sand 0.5 - 1 mm
• Fine fillers lt 5 mm
• Cement 1-100 mm
• Water
• Chemical admixtures

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Divide and Conquer

• Cement Paste Water Cement Particles
  Admixtures
• Mortar Cement Sand
• Concrete Mortar Aggregate

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Dissipative-Particle-Dynamics

• Mesoscopic particles represent clusters of
  molecules.
• Interactions conserve mass and momentum,
  isotropic and Galilean invariant produce
  hydrodynamic behavior consistent with
  Navier-Stokes equations.
• Molecular Dynamics Brownian motion velocity
  dependent dissipation.

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Dissipative Particle Dynamics
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Suspension of spherical aggregates
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Tracking of particle motion
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Relative viscosity vs. packing fraction
de Kruif, van Lersel, Vrij, Russel
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Tumbling of an aggregate under shear
Jeffreys tumble
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Ellipsoidal aggregates under shear
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High solid fraction suspension under shear
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Flow under gravity between rebars
Rebars
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Future Work

• Larger particle size distribution
• Add inter-particle interactions
• Model flow in more complex geometries
• Flow around rebars
• Multiphase flow