A new approach to concrete durability. Methodology and examples

This article with the outline a comprehensive, predictive, performance-based approach to the durability of reinforced concrete structures, based on the concept of durability indicators, and combining laboratory measurements and calculation codes (models). This approach was developed for the prevention of reinforcement corrosion and alkali-reaction degradation within the framework of the French Civil Engineering Association's working group on "Concrete design for a given service life - Durability indicators", and has been the subject of a Guide.

The proposed methodology for implementing this new approach to sustainability is presented in this article. It includes :

• a system of classes (accompanied by threshold values) defined for each durability indicator, to assess the "potential" durability of reinforced concrete;

• specifications relating to indicators, depending on the type of environment and service life required for the structure, in order to select or qualify concrete formulas for this structure.

The approach proposed for predicting durability in the design phase, or for diagnosing and assessing the residual service life of existing structures, whether degraded or not, is then presented. It is based on three essential tools:

• one or more predictive service life models ;

• the aforementioned sustainability indicators (model input data) ;

• life indicators (model outputs).

The characteristics required for the models are specified, and methods for measuring service life indicators, applicable in the laboratory on test specimens or on samples taken from structures, are also proposed.

Examples of the approach's application are also given in this article, in relation to the prevention of reinforcement corrosion induced by carbonation or chloride penetration in concrete.

As will be illustrated in this article, this new approach offers a "toolbox", i.e. a complete methodology for assessing and predicting sustainability.