Modelling time-to-cracking in brick masonry with corroding bed joint reinforcement

Clay brick facades often include bed joint reinforcement, especially over windows and other openings in the façade, which may corrode due to degradation from climatic exposure. Removal of corroded bed joint reinforcement from such facades is an invasive and costly measure. Heavily
damaged reinforcement must be removed for either structural, durability or aesthetic reasons. Parts of the bed joint reinforcement can however be left in the façade, if it can be shown that the risk for future damage is acceptably low. This will significantly reduce the amount of work needed and the retrofitting
costs. A dose-response model for prediction of corrosion induced cracking in reinforced brick masonry is presented, with relative humidity, temperature and oxygen supply in the vicinity of the reinforcement as influencing parameters. Corrosion depth, constituting the dose, is modelled by integration of the
effect of corrosion rate with respect to time. To describe the dependence of corrosion rate on the influencing parameters, models from the field of concrete research are used. The response, which can be seen as a limit state, is the corrosion depth required to create a crack due to tensile stresses generated by corrosion products. Due to scarcity of experimental data from the field of reinforced brick masonry, the critical corrosion depth is established using empirical data from the field of concrete research. To address this lack of a well-defined limit state, tests will be performed on clay brick specimens in a later part of the research project. The model’s ability to predict time-to-cracking
is demonstrated by comparison with data from field observations.