Environmental Impacts of Combined Repairs on Marine Concrete Structures

This paper presents an approach to assess environmental impacts in terms of CO2 resulting from applying combined repairs to extend service life of marine concrete structures. The service life is defined by considering chloride ion diffusion using the partial differential equation of the Fick's second law. However, the equation cannot simply be solved, when the concrete structures are repaired with three strategies, i.e., concrete cover replacement, silane treatment, or combinations of them. The difficulty deals with solving nonlinear chloride ion concentration profile and space-dependent diffusion coefficient after repairs. To remedy the difficulty, the finite difference method is used. By numerical computation, nonlinear chloride ion concentration profile can be treated point-wise. Based on the Crank-Nicolson scheme, a formulation for space-dependent diffusion coefficient can be derived. Using the aforementioned idea, space- and time-dependent chloride ion concentration profiles can be presented, and the extended service life of concrete structures after repairs can be computed. In repairs for extending the service life, the CO2 occurs due to repair material production and repair processing of three repair strategies. For comparing the performance of those strategies, the CO2 and cost are considered with the service life extension. Numerical examples and observation are finally presented.