Traditionally, the procedures for designing concrete mixtures, and indeed for designing concrete structures themselves, have focused primarily on compressive strength and other mechanical properties; durability issues received only secondary consideration. Durability of a structure implies that it remains fit for use for its intended purpose in the environmental conditions to which it is exposed over its entire service life, including anticipated maintenance, but without the need for major repair. The concrete industry is currently in the process of moving, very gradually, from prescriptive to performance specifications in the design of concrete mixtures. The move to performance-based durability design would be fully achieved by the limit state design approach and partially by the partial factor design approach. The limit state approach and service life design concepts in the performance-based codes provide the framework for the application of models developed by scientific research.