Critical review of the South African Concrete Durability Index tests
The Durability Index (DI) approach is a performance-based approach used in South Africa for specifying the durability of reinforced concrete structures with regard to service life and concrete quality. The approach comprises three DI tests which are used to measure the durability-related transport processes of permeation, absorption and ionic diffusion. These tests are the oxygen permeability index (OPI), water sorptivity index (WSI), and chloride conductivity index (CCI) tests, respectively. Much work has been done over the past two decades in developing the DI tests to the present stage, where they are being, and have been, used in large projects such as the Gauteng Freeway Improvement Project, which made use of the OPI and WSI tests as a basis for checking the quality of the concrete used in the major road upgrade project. Non-compliance with target values can result in rejection of the material or penalties imposed on the concrete supplier or contractor. This highlights the need for the DI tests to be accurate and reliable so that engineers have confidence in their results. This dissertation presents a critical review of the DI tests. The overall objectives were to critically examine the present DI testing regimes and identify and address areas of concern with the tests in order to make them more reliable. One of the major areas of concern related to specimen preconditioning: the 7-day oven drying regime and specimen saturation techniques have been called into question. Consequently, this work investigated the influence of the drying method and saturation processes on the DI results.
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