Performance-based durability testing, design and specification in South Africa: latest developments: Fid-Bau Portal

Performance-based durability testing, design and specification in South Africa: latest developments

Alexander, M.G. / Beushausen, H.

Over the last decade, an approach to improving the durability of reinforced concrete construction has been developed in South Africa. The philosophy involves the understanding that durability will be improved only when unambiguous measurements of appropriate cover concrete properties can be made. Such measurements must reflect the in situ properties of concrete, influenced by the dual aspects of material potential and construction quality. Key stages in formulating this approach were developing suitable test methods, characterising a range of concretes using these tests, studying in-situ concrete performance, and applying the results to practical construction. The paper discusses the latest developments in durability specification practice in South Africa and attempts to show a sensible way forward for practical application of the DI approach. The approach is an integrated one in that it links durability index parameters, service life prediction models, and performance specifications. As improved service life models become available, they can be implemented directly into the specifications. Concrete quality is characterised in-situ and/or on laboratory specimens by use of durability index tests, covering oxygen permeation, water absorption, and chloride conduction. The service life models in turn are based on the relevant DI parameter, depending on whether the design accounts for carbonation-induced or chloride-induced corrosion. Designers and constructors can use the approach to optimise the balance between required concrete quality and cover thickness for a given environment and binder system.