ABSTRACT
ABSTRACT The risk of failure of concrete infrastructures built in corrosive environments is increasing due to use of deicing salts, increased loads, inadequate maintenance and increased rate of deterioration due to climate change. Climate change leads to an increase in temperatures, which in turn leads to an increase in chloride diffusivity and rate of corrosion that yield an increase in probability of corrosion of reinforcing steel, concrete damage and a shortening of service life of concrete structures. The impact of temperature rise due to climate change on diffusivity is modeled using the Arrhenius relationship. Uncertainties in the parameters governing the service life, such as concrete cover depth, chloride threshold, chloride diffusion coefficient, surface chloride content are considered by modeling them as random variables. The optimum service life of concrete structures can be defined as the time at which the probability of corrosion reaches an acceptable value for different types of concrete, reinforcing steel and concrete cover depths. The time-dependent probability of corrosion of reinforcing steel embedded in concrete structures is formulated as a nonlinear optimization problem that is solved by the projected Lagrangian algorithm. The example of a concrete bridge deck is used to illustrate that the time-dependent probability of corrosion increases with temperature by 37% and 77% for life cycle temperature rises of 3°C and 6°C, respectively compared to the reference case at 23°C. To reduce this probability of corrosion, corrosion-resistant steel reinforcement, high performance or/and higher concrete cover depth can be used. For the case of bridge decks reinforced with corrosion-resistant steel, the corrosion probability is reduced by half after 40 years compared to that associated with black steel for the climate scenario with 6°C temperature rise. The final selection of an optimal design should take into account the life cycle costs incurred during the service life or life cycle of concrete infrastructures.
