Spherical and acicular representation of hydrates in a micromechanical model for cement paste: prediction of early-age elasticity and strength

Pichler, Bernhard; Hellmich, Christian; Eberhardsteiner, Josef

doi:10.1007/s00707-008-0007-9

Cited by 130 publications

(96 citation statements)

References 47 publications

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“…Calcium-silicatehydrates are present as a sole homogeneous aging phase. At this scale, C-S-H particles can either be considered as needles [38,39] or as spherical inclusions [6,7]. This is a long-standing and still open scientific debate.…”

Section: Microstructure Representationmentioning

confidence: 99%

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Uncertainty propagation of a multiscale poromechanics-hydration model for poroelastic properties of cement paste at early-age

Venkovic¹,

Sorelli²,

Sudret³

et al. 2013

Probabilistic Engineering Mechanics

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The durability of concrete materials with regard to early-age volume changes and cracking phenomena depends on the evolution of the poroelastic properties of cement paste. The ability of engineers to control the uncertainty of the percolation threshold and the evolution of the elastic modulus, the Biot-Willis parameter and the skeleton Biot modulus is key for minimizing the vulnerability of concrete structures at early-age. This work presents original results on the uncertainty propagation and the sensitivity analysis of a multiscale poromechanics-hydration model applied to cement pastes of water-to-cement ratio of 0.40, 0.50 and 0.60. Notably, the proposed approach provides poroelastic properties required to model the behavior of partially saturated aging cement pastes (e.g. autogenous shrinkage) and it predicts the percolation threshold and undrained elastic modulus in good agreement with experimental data. The development of a stochastic metamodel using polynomial chaos expansions allows to propagate the uncertainties of kinetic parameters of hydration, cement phase composition, elastic moduli and morphological parameters of the microstructure. The presented results show that the propagation does not magnify the uncertainty of the single poroelastic properties although, their correlation may amplify the variability of the estimates obtained from poroelastic state equations. In order to reduce the uncertainty of the percolation threshold and that of the poroelastic properties at early-age, engineers need to assess more accurately the apparent activation energy of calcium aluminate and, later on, of the elastic modulus of low density calcium-silicate-hydrate.

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Section: Microstructure Representationmentioning

confidence: 99%

“…The double integration of Eq. (27) is performed with respect to the approximation of Stroud [39,49].…”

Section: Localizationmentioning

confidence: 99%

Uncertainty propagation of a multiscale poromechanics-hydration model for poroelastic properties of cement paste at early-age

Venkovic¹,

Sorelli²,

Sudret³

et al. 2013

Probabilistic Engineering Mechanics

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“…As discussed in (Pichler et al 2009a), cylindrical pores imply the lower bound for the diffusivityrelated percolation threshold of cement paste, while spherical pores imply the respective upper bound, see also Fig. 7 for a graphical comparison of D hom paste according to Eq.…”

Section: Discussionmentioning

confidence: 94%

“…Such diffusivity tests are, as a rule, not directly characterized by the porosity f pore , but rather given in term of the initial water-to-cement mass ratio (w/c), at which the cement paste was produced, see Table 1. According to the famous Powers-Acker model (Powers and Brownyard 1948;Acker 2001), the water-to-cement ratio relates to the volume fractions of cement paste constituents "cement clinker" (cem), "water," "hydrates" (hyd), and "air," via (Pichler et al 2009a)…”

Section: Figmentioning

confidence: 99%

“…Explicit consideration of the latter has allowed for substantial improvements of microstructural models for the mechanics of cement paste and concrete (Sanahuja et al 2007;Pichler et al 2009a;Pichler and Hellmich 2011). The same is true for a micromechanical model of gypsum which considers the physically active (solid) parts of the microstructure as infinitely many non-spherical phases (Sanahuja et al 2010), while the physically non-active (fluid) parts were considered, for simplicity, as spheres.…”

Section: Introductionmentioning

confidence: 99%

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Self-Consistent Channel Approach for Upscaling Chloride Diffusivity in Cement Pastes

et al. 2017

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Chloride ingress into concrete is a major cause for material degradation, such as cracking due to corrosion-induced steel reinforcement expansion. Corresponding transport processes encompass diffusion, convection, and migration, and their mathematical quantification as a function of the concrete composition remains an unrevealed enigma. Approaching the problem step by step, we here concentrate on the diffusivity of cement paste, and how it follows from the microstructural features of the material and from the chloride diffusivity in the capillary pore spaces. For this purpose, we employ advanced self-consistent homogenization theory as recently used for permeability upscaling, based on the resolution of the pore space as pore channels being oriented in all space directions, resulting in a quite compact analytical relation between porosity, pore diffusivity, and the overall diffusivity of the cement paste. This relation is supported by experiments and reconfirms the pivotal role that layered water most probably plays for the reduction of the pore diffusivity, with respect to the diffusivity found under the chemical condition of a bulk solution.Keywords Diffusion · Homogenization · Chlorides · Multiscale modeling · Layered water List of Symbols Mathematical operators divDivergence operator, applied to a vector field div Divergence operator, applied to a second-order tensor field grad Gradient operator on the microscopic observation scale of pore space

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Numerische Simulation im Tunnelbau

Meschke¹

2013

Beton‐Kalender 2014

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Spherical and acicular representation of hydrates in a micromechanical model for cement paste: prediction of early-age elasticity and strength

Cited by 130 publications

References 47 publications

Uncertainty propagation of a multiscale poromechanics-hydration model for poroelastic properties of cement paste at early-age

Uncertainty propagation of a multiscale poromechanics-hydration model for poroelastic properties of cement paste at early-age

Self-Consistent Channel Approach for Upscaling Chloride Diffusivity in Cement Pastes

Numerische Simulation im Tunnelbau

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