A Multifield Model for Early-Age Massive Concrete Structures: Hydration, Damage, and Creep

A multifield model of the early-age behavior of massive concrete structures is presented. The hydration process and the thermal evolution are both described through a coupled chemo-thermal model that predicts the degree of hydration and temperature fields that are consistent with experimental measurements. The mechanical model is of the damage–plasticity type and relies on the assumption of additive strains. The classical evolution functions for damage and instantaneous plastic strain are introduced in effective stress space. The extended microprestress-solidification (MPS) theory is implemented to account for the effects of stress, temperature, and degree of hydration on the creep strain. To account for nonlinear creep at relatively high stress, a damage-dependent nonlinear creep function is introduced to couple damage and creep. The autogenous shrinkage and thermal strains are characterized by linear functions of degree of hydration and temperature, respectively. Moreover, the early-age evolutions of strengths and peak strain are also considered to be functions of hydration degree. The model is calibrated and validated through numerical simulations of simple creep tests and a three-dimensional finite element analysis of a massive concrete wall. The results suggest that the proposed model offers promise for the analysis of early-age cracking within massive concrete structures.