Modelling elasticity of a hydrating cement paste

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

“…However, the proposed model assumes different hypotheses with respect to the work of Sanahuja et al [15], such as: (i) a spherical elementary C-S-H particle at the nanometer scale. As demonstrated by Sanahuja et al [32], the shape of particles of polycrystals with packing density greater than 60% (as LD and HD C-S-H) is a second order parameter; (ii) a larger number of anhydrous phases and hydration products; (iii) spherical particles of HD C-S-H embedded into a matrix of LD C-S-H.…”

“…The approach adopted is inspired from underlying works in microporomechanics [1,9,10] and model applications to earlyage cement-based materials [6,15,16]. However, the proposed model assumes different hypotheses with respect to the work of Sanahuja et al [15], such as: (i) a spherical elementary C-S-H particle at the nanometer scale.…”

“…While providing good results for mid-to late-stages of hydration, this model lacked of precision at very early-age. Later on, Sanahuja et al [15,16] studied the impact of the shape of solid hydrates on the prediction of the solid percolation threshold and the elastic modulus of aging cement pastes. However, portlandite and ettringite were not considered among the hydration products responsible for setting in the model.…”

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

“…For the time being, we consider prescribing in our model an isotropic pore-scale diffusivity as reasonable model assumption because then the pore-scale diffusion coefficient can be simply back-calculated from the experimental data, not requiring the use of a more expensive optimization algorithm. We may also mention that our approach is fully consistent with the current state of the art in the mathematical modeling of concrete: In fact, our microheterogeneous formulation rests on the famous hydration model of Powers and Brownyard (1948) and Acker (2001), which has not only provided the basis for numerous, experimentally validated, micromechanical descriptions Sanahuja et al 2007;Pichler et al 2009b;Scheiner and Hellmich 2009), but has also been kind of corroborated by very recent statistical physics approaches (Ioannidou et al 2016). In the aforementioned micromechanics approaches, an RVE of cement paste is either composed of water pores, air pores, hydrates, and unhydrated cement (clinker) grains Pichler et al 2009b;Scheiner and Hellmich 2009), or of clinker grains embedded into a hydrate foam matrix, whereby the latter is, at a smaller scale, resolved into hydrates, water pores, and air pores; i.e., a hierarchical system of two RVEs is used to represent cement paste (Pichler and Hellmich 2011; Pichler et al (2009b) and Scheiner and Hellmich (2009), involving only one RVE representing the composite material cement paste.…”

“…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.…”