Durability of Concrete

尽管混凝土技术不断发展，但极端环境下的混凝土仍会过早劣化。部分原因是使用新材料时没有充分考虑副作用，但主要原因是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。水泥浆体基质和浆体-骨料界面区域的孔结构和由此产生的流体渗透阻力决定了混凝土的耐久性。在本提案中，将继续研究这些性能，并将其应用于抗氯离子侵入、钢筋腐蚀、冻融、碱骨料反应和抗硫酸盐性。耐久性的其他方面，如抗裂性（热和水分相关的收缩）和改进的耐久性性能规格也正在研究中。 具体而言，有几个研究重点领域：（1）开发测试方法，特别是与表征孔隙结构、通过混凝土的流体传输、碱-硅反应、盐结垢、抗硫酸盐性和体积稳定性相关的测试方法，（2）预测与化学外加剂组合的胶凝材料的新鲜和早期性能的性能，（3）开发用于评估低碱水泥在减轻碱-硅反应中的作用的程序，（4）增加混凝土中工业副产品和废料的使用，（5）改进暴露于氯化物环境的混凝土的剩余使用寿命的评估，（6）在规范和标准中制定和实施新的耐久性性能测试方法和做法。

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.