A practical carbonation model for service life design of reinforced concrete structures

Abstract

The “Durability Index” (DI) performance-based approach, developed in South Africa, involves the application of early-age concrete test methods together with service life prediction models, and links material properties directly with the expected service life of reinforced concrete (RC) structures under various environmental conditions. The Oxygen Permeability Index (OPI) DI test is based on permeation and relates to carbonation of concrete. As practised in South Africa (e.g. Committee of Transport Officials (COTO)), this approach requires durability considerations to be introduced in the design of the concrete mixture, and provides a quantification of the expected service life duration. This paper presents a design tool based on existing models for use in practical applications for service life design, assuming application of carbonation models and the OPI test method, and representing a probabilistic approach to performance-based durability design. The design tool can be applied for predicting the long-term performance of new RC structures as well as improving the basis for quality assessment of existing, newly built RC structures. This probabilistic approach to performance-based durability assessment is exemplified using actual data reported in the literature.