Hygro-chemo-mechanical deterioration processes in concrete: Modeling and computation

An understanding of the underlying causes of concrete deterioration is essential to perform meaningful durability design and/or evaluations of concrete structures. Furthermore, to quantitatively comprehend the condition of deteriorated concrete structures, the models for those deterioration processes need to be developed. It is the purpose of this study to model some of the deterioration processes of concrete, namely alkali-silica reaction (ASR), chloride-induced corrosion and shrinkage-induced damage. Also, implementation of parallel computation in finite element method is discussed.; A mathematical model which characterizes the effects of various influential parameters on the pessimum size effect of ASR and predicts the development of ASR expansion is proposed. The model emphasizes the chemomechanical coupling of the ASR expansion process, the size distribution of aggregates, and microstructural features of cement paste. The mechanical part of the model is developed based on a modified version of the generalized self-consistent theory. The chemical part of the model includes two opposing diffusion processes. One is the diffusion of chemical ions from pore solution into aggregate, and the other one is the permeation of ASR gel from the aggregate surface into the surrounding porous cement matrix. The balance between the two opposing diffusion processes determines the pessimum size of the aggregate and maximum expansion of the concrete.; Chloride-induced corrosion is one of the most important deterioration mechanisms in reinforced concrete structures. This part of study presents detailed theoretical models for predicting service life of reinforced concrete structures exposed to chloride attack. Three stages are considered in the corrosion process, namely the diffusion period, the rust accumulation period, and the crack propagation period. Two-way coupled diffusion equations are used to characterize the length of the diffusion period. For the rust accumulation period, the chemomechanical coupling between the formation of the rust and the development of the interface pressure is considered as the driving force. For the crack propagation period, the interface pressure induced by the rust expansion and the fracture resistance of the cracked concrete determine the rate of crack propagation.; Drying shrinkage of concrete occurs due to the loss of moisture and thus, it is controlled by moisture diffusion process. On the other hand, shrinkage affects moisture diffusion properties, the moisture capacity and humidity diffusion coefficient. This interactive effect is very important for the durability of concrete structures. The effect of drying shrinkage on the humidity diffusion coefficient is introduced by a scalar damage parameter, while the moisture capacity is evaluated by an analytical model based on non-equilibrium thermodynamics and minimum potential energy principle for a two-phase composite. The damage evolution due to the drying shrinkage is characterized in the framework of elastoplastic damage mechanics. The present model can predict that the drying shrinkage accelerates the moisture diffusion in concrete, and in turn, the accelerated drying process increases the shrinkage strain.; Finally, an implementation of the parallel programming in a computationally intensive finite element method is presented. The implementation details of Schur complement method in the parallel finite element algorithm are discussed. The advantages of parallel programming are demonstrated by numerical examples.