Effect of aggregate shapes on local fields in 3D mesoscale simulations of the concrete creep behavior

Abstract

Describing accurately the creep behavior of concrete is of significant importance for the evaluation of the long-term performance of structures. In this regard, a finer characterization of mesostructure effects and material non-linearity provides very insightful information. In this work, the effects of aggregate shapes on the creep response are studied using numerical simulations on 3D mesoscopic samples. The main focus is put on the assessment of the representativeness of generated samples versus real specimens obtained by tomography. Several mesostructures are generated by randomly distributing aggregates with different geometries, from simple spheres to realistic ones extracted from tomography. Creep simulations with finite element (FE) and Fast Fourier Transform (FFT) methods are then performed on different spatial refinements. Moreover, a classical linear viscoelastic (VE) and a viscoelastic-viscoplastic (VE-VP) behavior able to reproduce non-recoverable strains are adopted for describing the matrix behavior, to assess the relevance of a more accurate model. It is shown that numerical samples generated with tomographic aggregates may be regarded as a good approximation of the real specimen, while more ‘isotropic’ shapes, especially spherical, lead to significant differences at both local and macroscopic levels. Results obtained with FE and FFT methods are very close, indicating that while FFT is well adapted, FE remains attractive in this context. Finally, notable differences are observed between VE and VP response due to the development of residual strains in the matrix and correspondingly more limited strain redistribution, which indicates that VP-like models should be preferred to capture accurately the creep features at mesoscale.