Title:
Specifications of Concrete for Marine Environments: A Fresh Approach
Author(s):
Daksh Baweja, Harold Roper, and Vute Sirivivatnanon
Publication:
Materials Journal
Volume:
96
Issue:
4
Appears on pages(s):
462-470
Keywords:
blast furnace slag; chlorides; corrosion; fly ash; marine atmosphere
DOI:
10.14359/647
Date:
7/1/1999
Abstract:
There is significant debate around the world regarding the most appropriate test methods for assessing the performance of concretes in marine environments. Many papers have been presented on techniques, such as the ASTM C 1202 charge transfer test method and various chloride diffusion test methods focusing on their applicability in project specifications. Many views are held regarding the theoretical validity of such methods and the appropriateness or otherwise of their practical applications in specifications. Some even suggest that given the divergence of views on the different methods of performance based assessment of concrete for marine applications, prescriptive specification methods focusing on maximum water:binder ratio of concrete, minimum binder content, and binder type should be adopted. Specifiers, on the other hand, are looking to ways in which concrete for marine environments can be specified with greater confidence, thereby limiting their risk. Much research work has been conducted on chloride ion penetration into concrete and its relationships to embedded steel passivity and rate of corrosion. This paper summarizes work from a series of studies conducted at the University of Sydney. The focus of this work was on the long-term performance using half cell potential measurements, concrete resistivity, and the determination of gravimetric weight loss of steel through corrosion. Corrosion rates of steel in concrete were also measured using anodic polarization techniques. Concretes considered were made with a range of commercially available portland cement and supplementary cement materials. Using the previously-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 method for designing and assessing concretes for critical marine structures based on the information is reported. Use of this method will lead to improved specifications for concrete when compared with existing design specifications.