Specification of concrete for marine environments: A fresh approach

There is significant debate around the world regarding the most appropriate test methods for assessing the performance of concretes in marine environm ents. Many papers have been presented on techniques such as the ASTM C 1202 charge transfer test method: and various chloride diffusion test methods f ocusing on their applicability in project specifications. Many views are he ld regarding the theoretical validity, of such methods end the appropriaten ess of their practical applications in specifications. Some even suggest th at, given the divergence of views on the different methods of performance-b ased assessment of concrete for marine applications, prescriptive specifica tion methods focusing on maximum water-binder ratio of concrete, minimum bi nder content and binder type should be adopted. Specifiers, on the other ha nd, are looking to ways in which concrete for marine environments can be sp ecified with greater confidence, thereby limiting their risk. Much research work has been conducted on chloride ion penetration into conc rete and its relationships to embedded steel passivity and rate of corrosio n. This paper summarizes work from a series of studies. The focus of this w ork was on the long-term performance of reinforced concrete under high-chlo ride conditions. Work included the monitoring of concrete performance using half-cell potential measurements, concrete resistivity, and the determinat ion of gravimetric weight loss of steel through corrosion. Corrosion rates of steel in concrete were also measured using anodic polarization technique s. Concretes considered were made with a range of commercially available po rtland cement and supplementary cementitious materials. Using the previousl y mentioned information, concretes were classified on the basis of observed long-term performance based on resistivity and the time taken for embedded steel to reach a probable active corrosion state. The development of a met hod for designing and assessing concrete for critical marine structures bas ed on the information is reported. Use of this method will lead to improved specifications for concrete when compared with existing design specificati ons.