Carbonation is one of the many reasons of reinforcement corrosion in concrete structures. Due to the coupling effects of moisture, heat and carbon dioxide transport in concrete, the modeling of this problem is a rather challenging task. A nonlinear finite element approach is adopted here for tracing the spatial and temporal advancement of the carbonation front in concrete structures with and without cracks. A two-dimensional Windows-based finite element computer program, called CONDUR, is developed and the results obtained from the program are compared with available experimental data. The program is designed to be flexible and comprehensive in its scope.