A challenge to the current progress towards sustainability of built environment is to quantitatively predict the long-term behavior of the critical concrete structures, e.g., large-span prestressed box girders, super-tall buildings, nuclear reactor containments, and radioactive waste repositories. An accurate prediction of multi-decade performance requires realistic approximation of the unique porous microstructure of concrete, which transforms with its hygrothermal evolution. To minimize the phenomenological formulation in constitutive modeling and ameliorate the computational burden in numerical simulation, a multi-scale model of concrete, with a focus pinned on mesoscale, is proposed in this study to break down the long-term behavior of concrete to the time dependent mechanics of its different phases. In this model, concrete microstructure is represented by three material phases: coarse aggregate, mortar matrix, and the interfacial transition zone (ITZ) between the first two. In the framework of the classic continuum micromechanics, a Mori-Tanaka type homogenization scheme, enriched by continuous retardation spectrum method based on Laplace transform and Widder's approximation, is first formulated to capture the aging viscoelasticity of the representative unit cell of concrete which includes one aggregate only. The stress concentration in the ITZ, where micro-cracking will initiate and accumulate, is calculated by exterior point Eshelby solution, and then the corresponding damage strain in ITZ is taken into account as a smeared effective strain on the aggregate. The proposed multi-scale material model is incorporated into ABAQUS, and good results are obtained in simulations of some benchmark matrix-inclusion problems. Its effectiveness to realistically approximate the concrete long-term performance is also illustrated in a structural analysis of a prestressed concrete member.
展开▼
