A metallurgical approach to the durability of reinforced concrete

提高钢筋混凝土耐久性的冶金方法

• 批准号: RGPIN-2015-04862
• 负责人: Hansson, Carolyn
• 金额: $ 2.19万
• 依托单位: University of Waterloo
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=683331
• 关键词: metallurgical; approach; durability; reinforced; concrete

Summary ***    The application of rock salt and, more recently, concentrated brines to our highways and bridges is instrumental in high deterioration levels of concrete and carbon steel reinforcement (rebar). The deterioration arises from the ingress of chlorides and breakdown of the very thin film of oxides on the steel surface in concrete which normally protect the steel from rusting. The result is that the highway structures and parking garages in the Windsor to Montreal corridor have the greatest accumulation of salt of anywhere in North America and correspondingly high deterioration rates. ***    At the same time, the Canadian Highway Bridge Code has increased the required service life of highway bridges to 75 years and is proposing to increase it further to 100 years. Consequently, transportation authorities are interested in using more corrosion resistant alloys as rebar to limit the need for frequent maintenance and the associated traffic delays. Despite the significantly lower lifetime costs of a structure reinforced with these alloys, the greatest obstacle to their use is the initial cost. To address this problem, steel companies are developing stainless steel grades with less expensive alloying components, but the authorities are reluctant to install untested alloys in structures intended to last for 75 years or more. A number of research groups in Europe and North America (including the applicant's) have been investigating the relative corrosion performance of the newer alloys in short-term laboratory tests. However, these tests use various methods to accelerate corrosion and typically consist of three to five years exposure to salts at most, but sometimes are as short as 3 - 4 days. Extrapolating the results of accelerated tests to real world exposure for 3/4 century leaves many questions. ***    Therefore, in order to better predict the long term behaviour of stainless and corrosion resistant reinforcing alloys, the goal of the proposed research program is to define their metallurgical and electrochemical state when they are embedded in concrete and, eventually, exposed to the de-icing salts. Determining the nature of the passive films in-situ in a high pH environment, with and without chlorides, will be challenging and require modification to traditional methods. Another major obstacle to this research will be to actually achieve corrosion in these highly resistant alloys without radically changing the conditions. These data are needed in order to determine their corrosion rates. Training the next generation of engineers who will implement these groundbreaking advances is one important outcome. Another is that the results of this study will permit infrastructure designers to specify the most cost-effective materials for particular applications depending on the severity of the local climate and the desired service life of the structure. ***    **

摘要***岩盐的应用，最近将盐水集中在我们的高速公路和桥梁上，在混凝土和碳钢钢筋的高清晰度（Rebar）中发挥了作用。该定义是由氯化物的入口以及氧化物在混凝土中钢表面非常薄的薄膜的分解而产生的，该氧化物通常可以保护钢免受生锈。结果是，温莎到蒙特利尔走廊的高速公路结构和停车场的盐在北美任何地方的盐分最大，并且相应高清晰度。 ***同时，《加拿大公路桥法典》将高速公路桥梁的所需使用寿命提高到了75年，并建议将其进一步增加到100年。因此，运输部门有兴趣使用更多的耐腐蚀合金作为钢筋，以限制对频繁维护的需求和相关的交通，尽管这些合金加强的结构的终身成本明显降低，但使用的最大障碍是最初的成本。为了解决这个问题，钢铁公司正在开发不锈钢等级，具有较便宜的合金组件，但是当局不愿在旨在持续75年或更长时间的结构中安装未经测试的合金。欧洲和北美（包括申请人）的许多研究小组一直在研究短期实验室测试中新合金的相对腐蚀性能。但是，这些测试使用各种方法来加速腐蚀，通常最多包括三到五年的盐，但有时短达3-4天。将加速测试的结果推断到3/4世纪的现实世界暴露的结果中留下了许多问题。 ***因此，为了更好地预测不锈钢和耐腐蚀的增强合金的长期行为，拟议的研究计划的目标是在将它们嵌入混凝土中，并最终暴露于脱水盐时，定义它们的冶金和电化学状态。在高pH环境中确定被动膜的性质，具有和没有氯化物的情况，将受到挑战，需要对传统方法进行修改。这项研究的另一个主要障碍将是在这些高度耐药的合金中实际实现腐蚀，而不会从根本上改变条件。为了确定其腐蚀速率，需要这些数据。培训将实施这些开创性进步的下一代工程师是一个重要的结果。另一个研究的结果将允许基础设施设计人员根据当地气候的严重程度和结构的所需使用寿命为特定应用指定特定应用的最具成本效益的材料。 *** **