Methodology for Designing Structures to Withstand Extreme Environments: Performance Based Specifications

Existing guidelines in BS 8500 allow the selection of concrete mix based on variables such as compressive strength, maximum water to binder ratio, minimum cement content and minimum cover thickness. This approach does not guarantee the durability and expected performance of the concrete structure in a given environment. One alternative is to develop performance- based specifications that supplement the existing guidelines in BS 8500, by specifying the required performance of concrete in terms of measurable properties such as resistance to environmental penetrations. This paper demonstrates one of such methodology for developing performance-based specifications for concretes exposed to marine environments. Chloride ingress related durability problem being critical in a marine environment, the reliability and repeatability of the different test methods for assessing the rate of chloride ingress is discussed first. Furthermore, a numerical simulation model is used to explore the test data to obtain long-term chloride ingress trends. Based on this, guidelines for selecting appropriate concrete mixes for a marine exposure is presented and discussed.