Concrete in Aggressive Aqueous Environments
PSC Technical committee : Performance-based specifications and control of concrete durability
Chairman : Dr. H. Beushausen, Secretary : Ing. L. Fernandez Luco
guidelines for the specification of the penetrability and thickness
of the concrete cover, as function of the exposure conditions and service
life design, and for its compliance control through suitable site and/or
For the particular, but significant, case of steel corrosion, the service life of the member depends also on the thickness of the concrete cover.
Currently, the specification of durability in the most widespread Codes and Standards (ACI-318 and EN 206-1) is based mainly on establishing constraints to the proportions of the concrete as function of the severity of the exposure. This approach ignores, to a large extent, the different performance of the different cement types and of the mineral components added to the cements or to the concrete itself. Moreover, it is virtually impossible to perform an effective control of the w/c ratio and/or cement content in practice.
The routine control of concrete quality is based on testing (typically for strength) moulded specimens, compacted and cured in a near-perfect, standard manner. As sketched in Figure 1, such specimens do not represent the real quality of the vital 'covercrete'. Thus, the important impact of the application of the correct concreting practices (placing, compaction, finishing, curing, etc.) remains largely ignored.
All this explains, to a large extent, the recurrent problems of lack of proper durability of concrete structures. The obvious solution would be to check the penetrability and thickness of the 'covercrete' in the real structure, as final product, which can only be done on site or on drilled cores.
Previous work of RILEM TCs has identified suitable test
methods to measure the 'penetrability' of the 'covercrete:
The latter also investigated the suitability of 'covermeters'
to assess the depth of the concrete cover.