Concrete weight coating: Mitigation of alkali-silica reaction and sulfate attack

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Undersea oil and gas pipelines typically are coated with high density concrete to counteract buoyancy. These coatings must be durable over the life of the pipeline in an aggressive seawater environment. As these coatings are often applied in various locations around the world and involve fairly large volumes of concrete, local materials must be used. The aggregates and cementitious materials must be tested for their durability when used together in concrete pipe coatings. Alkali-silica reaction and both internal & external sulfate attack are well known causes of deterioration in normal concrete but not much is known or studied as to the impacts of these chemical reactions on the deterioration and expansion of dry mix concrete used by ShawCor for its concrete coatings. In this project, ShawCor will provide both raw materials from specific locations and cast simulated pipe coatings into test specimens. The aggregate materials have already been tested by some standard test methods, but the University of Toronto will evaluate them by new, non-standard rapid methods, that may be of use to Shawcor in future investigations. In addition, the resistance of the simulated dry-cast pipe coatings will be investigated for their resistance to both alkali-silica reaction and both internal & external sulfate attack. The results of this research will help ShawCor determine the appropriateness of their existing materials specifications and in the development of new specifications.