Modelling synergistic effects of carbonation/chloride penetration and frost attack for service life design of concrete bridges

The traditional approach for the service life design of a reinforced concrete structures is typically based on the modelling of a dominating degradation mechanism or several degradation mechanisms separately. However, in real-life exposure, reinforced concrete structures are subject to the simultaneous effect of several degradation mechanisms. The Finnish DuraInt research project (Effect of Interacted Deterioration Parameters on Service Life of Concrete Structures in Cold Environments, 2008 - 2011) was setup to understand the combined effect of degradation mechanisms such as, frost attack (both internal frost attack and frost scaling), carbonation and chloride penetration, on concrete performance. In this paper the effect of frost attack on carbonation and chloride penetration is analysed. The influence may be substantial and should be taken into account when concrete is exposed to frost attack. A part of the DuraInt research project dealt with the modelling of the combined effects of degradation mechanisms. Based on the results of laboratory and in situ exposure tests, the effects of frost attack on the rate of carbonation and chloride penetration as an interacted degradation were developed. A procedure for integrating the synergistic effect of both internal frost attack and frost scaling on carbonation and chloride penetration for the service life design of reinforced concrete structures is presented based on the use of interaction factors. Results showed that, if frost attack is rapid, it is usually the dominating degradation mechanism, marginalising reinforcement corrosion initiated by carbonation or chloride penetration. If frost attack proceeds slowly, reinforcement corrosion can become dominate and the interaction effects should be considered in the service life design of reinforced concrete