Thesis (M.Eng.) - Asian Institute of Technology, 1999

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Civil Engineering

Cementitious materials are generally the crucial factors that influence several deterioration mechanisms controlling the durability of concrete. Considering corrosion is one of the important factors in reinforced concrete structures as the long term deterioration causes, the governing equation of moisture and oxygen transport through the concrete microstructure are formulated. The core of this formulation is based upon thermodynamic couplings of moisture transport, powder material hydration and the microstructure formation phenomenon's. The transport of oxygen is formulated considering oxygen concentration difference the equilibrium between gas phase and dissolved phase oxygen is considered and using Henry's law and Ideal gas law the dissolved oxygen is formulated. The corrosion model is based upon a micro-cell approach. An integrated numerical procedure based on the finite element method is used to obtain the solutions for this highly inter-linked theoretical framework. The proposed framework can take into account the effects of various macro material parameters like mix proportions, etc. with very few assumed functional relationships. Preliminary simulations of oxygen transport show the versatility and extensibility of the proposed scheme and important of the evaluation of oxygen concentration in reinforces concrete structure. Oxygen transport model is implemented in DuCOM, Durability Model of Concrete, and it was verified using the experimental results available. Finally, it was found that the model gives relatively less than the experimental results in the verification of diffusion coefficient and it can be used for the evaluation of rate of corrosion in terms of durability viewpoint and etc.