PROF. CARMEN ANDRADE is Research Professor of the National Research Council of Spain (CSIC) and Dr. in Industrial Chemistry. She is also an adviser to the State Secretary of Universities of the Ministry of Science and Education. She has been working in the areas of Reinforcement Durability from the seventies and has written numerous papers on the related area of Assessment of Steel Corrosion, Repair and Rehabilitation. She was awarded the Doctorate “Honoris Causa” of the Technical University of Trondheim-Norway in 2003 and of the University of Alicante-Spain in 2006. She also awarded the Price “Robert L’hermite” of Rilem in 1986 for young scientist having produced a relevant and original work and the Price to Civil Engineering of Portugal “Manuel Rocha” of Portugal in 2002. She has been the President of Rilem and of the Liaison Committee, President of UEAtc and WFTAO, Director of the Institute of Construction Science of Spain, Chairman of the RILEM TC- 178 on Measurement and Testing Chloride Penetration in Concrete, Chairman of the RILEM TC on “Model assisted integral service life prediction of steel reinforced concrete structures with respect to corrosion induced damage” and International Coordinator of the Iberoamerican Subprogram on Corrosion of CYTED.

TYPES OF MODELS OF SERVICE LIFE OF REINFORCEMENT: THE CASE OF THE RESISTIVITY

ABSTRACT 

The design of concrete structures is usually made by means of a performance approach based on strength tests carried out following testing conditions agreed by convention. A similar approach should also be followed in the case of durability design regarding reinforcement corrosion. This type of consideration enables the definition of a four level methodology for design against reinforcement corrosion in parallel with that followed for strength design. Levels from I to IV are proposed: a) level I would be the prescriptive method already given in present codes based on “deemed-to-satisfy” rules, b) level I is that where still not quantification of the time to reach a limit state is explicit but the minimum life time is assured through performance based tests, c) level III would be the level in which the calculation of aggressive ingress through models having explicit the time is made and d) level IV includes the verification that the resistance of the cover thickness against the penetration of aggressive substances is higher than the environmental action effect including probabilistic treatments. For level II and III the measurement of the electrical resistivity results a very suitable proposal due to this parameter can be measured in a non destructive test and serves to quality control. It is not only a performance test (level II) but it can be included in models of both the initiation and propagation periods. For the time to corrosion onset, the electrical resistivity represents the porosity and its connectivity and therefore can be used to model transport processes. It also results very suitable for measuring concrete aging and then accounting for the reduction of the diffusion coefficient with time. Concerning the propagation period, the electrical resistivity is an indication of the moisture content of concrete and therefore, it has a certain relationship with the corrosion cement. A model is proposed in which the resistivity is introduced in the square root of time law.