Multiphase modeling of the effect of external loading on the shrinkage of concrete and its consequences for modeling tensile creep

Abstract

Multiphase modeling is a powerful framework for the simulation of the early-age and long-term behavior of concrete. Nevertheless, state-of-the-art multiphase models do not capture the experimentally observed instantaneous change in internal relative humidity upon external loading, which also manifests in the lack of predicting load-induced shrinkage. The approach presented in this publication is a step to overcome this deficiency. It is based on a poromechanical multiphase model for coupled creep and shrinkage of concrete, which is enhanced by a strong hygro-mechanical coupling, introduced via a load-dependent desorption isotherm. The enhanced model is evaluated for sealed and drying uniaxial compressive and tensile creep tests. Instantaneous changes in internal relative humidity upon loading are recovered by the enhanced model. In compression, the influence on the mechanical response is small. In contrast, the representation of tensile creep is significantly improved by considering load-induced shrinkage.