ENVIRONEMTAL IMPACTS DUE TO COMBINED REPAIRS FOR EXTENDING SERVICE LIFE OF CONCRETE STRUCTURES UNDER MARINE ENVIRONMENT

Abstract eng:
This paper presents an approach to assess environmental impacts in terms of CO2 resulting from applying combined repairs in order to extend service life of concrete structures under marine environment. In the paper, the service life is first defined by considering the mechanism of chloride ion diffusion based on the partial differential equation (PDE) of the Fick’s second law. However, the PDE cannot simply be solved, when concrete structures are repaired with three repair strategies, i.e., concrete cover replacement, silane treatment, or combinations of them. The difficulty is encountered in solving nonlinear chloride ion concentration profile and space dependent diffusion coefficient after repair. In order to remedy the difficulty, the finite difference method is used. By virtue of numerical computation, nonlinear chloride ion concentration profile can be treated point-wise. And, based on the Crank-Nicolson scheme, a proper formulation embedded with space dependent diffusion coefficient can be derived. By using the aforementioned idea, space and time dependent chloride ion concentration profiles can be calculated and presented, and the extended service life of concrete structures after repairs can be computed. In applying repairs to extend 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, both of the CO2 and cost are taken into account in addition to considering the service life extension. Numerical examples and observation are finally presented.

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