Reliability Analysis for Service Life of Concrete Structures Subject to Various Carbon Dioxide Concentrations

Carbonation is one of the factors that can reduce the service life of reinforced concrete structures, especially in urban environments where carbon dioxide (CO2) concentrations are elevated. While concrete is generally considered to be resistant to carbonation under normal atmospheric conditions, in polluted urban environments and accelerated laboratory conditions, carbonation can occur at accelerated rates. Concentration of carbon dioxide (CO2) can have a significant impact on the rate at which carbonation occurs. There are no current guidelines for determining the carbonation rate in reinforced concrete as a function of CO2 concentrations. This work presents a risk-based framework that can be used to quantify carbonation depths and rates for various levels of CO2. This paper also identifies the key variables that affect the service life of reinforced concrete structures, from the point of view of carbonation and the resulting corrosion. These variables include the quantities of the various hydrated/anhydrous phases and the effective diffusion coefficient of the cementitious system. Monte-Carlo simulations are also performed to identify the change in time to carbonation with change in both CO2 concentration exposure and the concentrations of the hydrated and anhydrous phases of concrete.