A critical appraisal of the developments in durability design, specification, construction and testing of concrete structures in South Africa

Abstract

The costs associated with the repair of deteriorating concrete structures have been reported to be substantial; however, the costs resulting from poorly designed or executed repairs may be even higher. Therefore, it is important to consider durability of concrete in the design and construction of concrete structures. Concrete durability is the capability of concrete to maintain serviceability over a specified period of time without showing significant deterioration. The aim of this research was to consolidate knowledge from work done in durability design, specification, construction and testing of concrete structures in South Africa; and investigate the application of this knowledge in practice. The method selected to investigate this was surveys in the form of structured questionnaires issued through electronic mails. The survey samples amongst stakeholders were selected by stratified random sampling which ensured a reduced likelihood of bias. Survey samples were selected as follows: Consulting Engineers (Sample size - 21, response rate – 86%); Tertiary Institutions (Sample size - 8, response rate – 100%); Contractors (Sample size - 19, response rate – 33%); Readymix Concrete Suppliers (Sample size - 9, response rate – 33%); Cement Suppliers (Sample size - 4, response rate – 75%); and Concrete Admixture Suppliers (Sample size - 4, response rate – 100%). From the data analysis, all stakeholders demonstrated awareness in the subject of durability of concrete as it was found that durability design concepts are incorporated through a careful selection of materials, consideration of the environment to which a structure will be exposed and careful planning of construction processes. The current methods in practice for design, specification, construction and testing of concrete were found to follow a ‘hybrid’ approach; which is a combination of prescriptive and performance-based approach. In general, the responses from the different stakeholders show similarities in terms of awareness of the need to have durable concrete, but this awareness is not being implemented by applying measureable durability-related properties of concrete to evaluate its penetrability. With the DI testing methods being incorporated into SANS standards, it is expected that the industry implement these tests in construction projects with the aim of achieving durable concrete. Also, learners in tertiary institutions should be introduced to these test methods as a step towards creating awareness in industry in which they eventually practice.