French national project 'PERFDUB' on performance-based approach : interest of old structures analysis for the definition of durability indicators criteria

The French National Project PERFDUB aims at setting up a methodology for justifying durability of concrete structures within a performance-based approach. The final objective is to make the performance-based specification operational and more commonly used by bringing together the current knowledge and feedback, to fill remaining gaps. This methodology relies on physical and chemical material properties which are called regarding the environmental conditions of the concrete structure. A major part of work in PERFDUB is to define durability criteria based on laboratory tests (durability indicators or accelerated ageing tests) in function of exposure classes and expected lifetime. This article deals, on the one hand, with the analysis of durability test results obtained from cores drilled out of ancient civil engineering concrete structures (built between 1912 and nowadays) compared with corrosion state of reinforcement. On the other hand, modelling works are presented dealing with carbonation, chloride ingress and corrosion rate (since design service life is presently considered to be defined by the time before appearance of first cracks induced by steel corrosion). The proposed durability criteria are taking into account both approaches, in order to benefit from all the available feedback on old structures and cross-check results obtained from theoretical modelling work. The aim is to ensure a soft transition between current practices and design based on performancebased approach. This study is closely related to work in progress on Exposure Resistance Class (ERC) at European level.