Numerical solution of mass transport equations in concrete structures

To calculate the service life of reinforced concrete (RC) structures, the process of reinforcement corrosion was modeled using a numerical formulation of the associated mass transport partial differential equations. Migration of chlorides, moisture and heat transfer within concrete, resulting from seasonal variations in the surface conditions of the RC member, form a coupled boundary-value problem, which was solved in space using a finite element formulation and in time using a finite difference marching scheme. The stage of active corrosion was modeled by including in the numerical algorithm of the FE formulation the mass conservation equation that describes diffusion of oxygen in the concrete cover. The paper presents details of the FE formulation and computed results from selected case studies.