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

海底油气管道通常涂有高密度混凝土以抵消浮力。这些涂层必须在恶劣的海水环境中保持耐用。由于这些涂料通常应用于世界各地的不同地点，并且涉及相当大体积的混凝土，因此必须使用当地材料。当骨料和胶凝材料一起用于混凝土管道涂层时，必须对其耐久性进行测试。众所周知，碱-硅反应和内外硫酸盐侵蚀是普通混凝土劣化的原因，但对于这些化学反应对ShawCor用于混凝土涂层的干混混凝土劣化和膨胀的影响，所知或研究的并不多。

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.