Performance-Based Concrete Mix and Cover Design in Saline Exposure: Why and How?

RC structures, in general, are susceptible to chloride-induced corrosion in saline/marine exposure due to their inherent permeability characteristics. The corrosion initiates within a RC element once the chloride concentration at the surface of embedded reinforcement reaches to a critical value. Such initiation of corrosion is usually minimized following two techniques: (i) by reducing rate of diffusion of chloride ions through concrete matrix and (ii) by providing adequate cover so that chloride ions would require longer travel distance to reach the surface of embedded rebars. Chloride diffusivity is usually reduced by selecting proper binder types that would guarantee long term pore refinement through pozzolanic reactivity. In case of cover requirement, it should be designed considering both construction feasibility and economy. Hence, in order to ensure design service life of a RC structure in saline conditions, a concrete mix needs to be properly proportioned with appropriate binder types that would keep the required cover values within feasible limit. A performance-based design approach can ensure such suitable combination of concrete mix proportions and cover requirements. However, no performance-based guidelines for marine concrete are available in Bangladesh focusing specific demand of the country. Considering the significance of the subject matter, an attempt has been made in this article to discuss the importance of performance-based design and techniques to achieve it based on outcomes of the previous studies.