Durability of Concrete

尽管混凝土技术有所发展，但极端环境下的混凝土仍在过早退化。在某种程度上，这是由于在使用新材料时没有充分考虑到副作用，但主要是由于使用了不适当的测试、规格或施工方法，以及对影响耐久性的所有因素缺乏了解。水泥浆体基质和膏体-骨料界面区域的孔隙结构和由此产生的流体渗透阻力决定了混凝土对大多数破坏原因的耐久性。在本提案中，将继续研究这些性能在抗氯化物侵入、钢筋腐蚀、冷冻和解冻、碱集料反应和耐硫酸盐方面的应用。耐久性的其他方面，如抗裂性（热和潮湿相关的收缩）和改进的耐久性性能规格也在研究中。

In spite of developments in concrete technology, concrete in extreme environments continues to prematurely deteriorate. In part, this results from the use of new materials without adequate consideration of side effects, but mostly from the use of inadequate tests, specifications or construction methods, and also from a lack of understanding of all the factors which influence durability. The pore structure and resultant fluid penetration resistance of the cement paste matrix and paste-aggregate interfacial regions govern the durability of concrete to most causes of distress. In this proposal, these properties will continue to be studied with applications in resistance to: chloride ingress, reinforcement corrosion, freezing and thawing, alkali-aggregate reactions, and sulphate resistance. Other aspects of durability such as crack resistance (to thermal and moisture-related shrinkage) and improved durability-based performance specifications are also being studied. Specifically, there are several areas of research focus: (1) development of test methods, especially related to characterizing pore structure, fluid transport through concrete, alkali-silica reaction, salt scaling, sulphate resistance, and volume stability, (2) prediction of performance of fresh and early-age properties of cementitious materials in combination with chemical admixtures, (3) developing procedures for evaluating the role of low-alkali cements in mitigating alkali-silica reaction, (4) increased use of industrial by-products and waste materials in concrete, (5) improvements to evaluation of residual service life of concretes exposed to chloride environments, (6) development and implementation of new durability performance test methods and practices in codes and standards.