In this paper the conflicting
requirements for the characteristics of concrete to ensure
durability versus
the
requirements to resist accidental actions are being discussed. The
conclusion is that the selection of concrete mix, structural detailing,
compaction, curing and other
important decisions must be taken with the overall
aim to ensure a high level of safety and minimum lifetime costs. The
methodology for achieving this optimum is risk assessment and risk management
during the period of use, which takes into account the material models, the
foreseen characteristic performance and the possible events, and their
consequences. In this context it is important that accidents are rare, whereas
ageing is an event which is foreseeable and thus has a high probability. Other
factors, being individual for the type of structure and the type of accident
considered, are important too, but for most structures dense durable concrete
will be the optimal choice.