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

海底石油和天然气管道通常涂上高密度混凝土，以抵消浮力。在恶劣的海水环境中，这些涂层必须在管道的整个使用寿命内耐用。由于这些涂层经常在世界各地应用，并且涉及相当大量的混凝土，因此必须使用当地材料。当集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。碱-硅反应和内外硫酸盐侵蚀都是普通混凝土劣化的众所周知的原因，但关于这些化学反应对ShawCor用于混凝土涂层的干拌混凝土劣化和膨胀的影响，人们了解或研究得很少。 在这个项目中，ShawCor将提供来自特定地点的原材料，并将模拟管道涂层浇注到试件中。集料材料已经通过一些标准测试方法进行了测试，但多伦多大学将通过新的、非标准的快速方法对其进行评估，这可能对ShawCor在未来的调查中有用。此外，还将考察模拟干浇注管道涂料的耐碱-硅反应和抗内外硫酸盐侵蚀的性能。这项研究的结果将帮助ShawCor确定其现有材料规格的适当性，并在开发新的规格时使用。

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.