Investigation of the effect of aggregates' morphology on concrete creep properties by numerical simulations

Abstract

International audiencePrestress losses due to creep of concrete is a matter of interest for long-term operations of nuclear power plants containment buildings. Experimental studies by Granger (1995) have shown that concretes with similar formulations have different creep behaviors. The aim of this paper is to numerically investigate the effect of size distribution and shape of elastic inclusions on the long-term creep of concrete. Several microstructures with prescribed size distribution and spherical or polyhedral shape of inclusions are generated. By using the 3D numerical homogenization procedure for viscoelastic microstructures proposed by Šmilauer and Bažant (2010), it is shown that the size distribution and shape of inclusions have no measurable influence on the overall creep behavior. Moreover, a mean-field estimate provides close predictions. An Interfacial Transition Zone was introduced according to the model of Nadeau (2003). It is shown that this feature of concrete's microstructure can explain differences between creep behaviors

Estimating the mechanical properties of hydrating blended cementitious materials: An investigation based on micromechanics

“…The considered periodic unit cell features 597 spherical inclusions packed to a volume fraction of 61% thanks to the Lubachevsky-Stillinger algorithm (Fig. 2.2) [96,97]. Periodic boundary conditions are applied to the unit cell, the macroscopic loading being an uniaxial stress Σ XX .…”

“…Then, the FFT algorithm [98,99] is applied to compute the elastic response of the unit cell, that is the values of the stress field for each voxel on a regular 160 × 160 × 160 grid. The behavior of "grey voxel", overlapping on both the matrix and the inclusions, is set according to the Reuss bound, using 64 sensing points in each voxel to estimate the local volume fraction as in [97]. The estimated overall Young modulus is about 34.4GPa, comparable to 33.5GPa for a Mori-Tanaka scheme, which corresponds to the Hashin-Strikman lower bound in this case.…”

Microstructural effects in the simulation of creep of concrete

“…The question is also raised for creep, and cannot generally be assessed by analytic homogenization scheme without additional refinement like the tri-sphere model proposed by Le Roy [52]. In a recent paper, Lavergne et al computed apparent properties of composites simulated in 3D [12]. They found that the macroscopic creep properties were somehow independent of the particle size distribution, but in their work, the ratio between the smallest and largest particle was around 1/10, while the particle size distribution of aggregates in concrete spans two orders of magnitude.…”

“…In meso-scale simulations, aggregates are typically simulated as circles or spheres, as they are the easiest shape to manipulate, which however cannot provide an anisotropic behaviour. Notable exceptions include works with randomly generated polygonal aggregates [2,4,13], or using images of the material microstructure [1,67,12].…”

“…Increasingly, concrete degradation phenomena are approached with numerical methods in which concrete is modelled as a twoor three-phase composite containing aggregates, cement paste and perhaps a transition zone between them. Examples include prediction of the material strength [1][2][3][4][5][6][7][8][9], visco-elastic properties [10][11][12], drying shrinkage [13,14], or damage due to ASR [15][16][17], high temperature [18], leaching [19], or irradiation [20,21]. These multi-scale models are based on our best understanding of the physical processes concrete undergoes, therefore, they are suitable for long-term extrapolation as well as interpretation of experimental results.…”