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: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=613214
• 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.

总结 岩盐和最近的浓缩盐水在我们的高速公路和桥梁中的应用有助于混凝土和碳钢钢筋（钢筋）的高度劣化。腐蚀是由于氯化物的进入和混凝土中钢筋表面上非常薄的氧化物膜的破坏造成的，氧化物膜通常保护钢筋不生锈。其结果是，温莎至蒙特利尔走廊的公路结构和停车场在北美任何地方都有最大的盐积累，相应地也有很高的恶化率。 与此同时，《加拿大公路桥梁规范》将公路桥梁的使用寿命要求提高到75年，并建议进一步提高到100年。因此，运输当局有兴趣使用更耐腐蚀的合金作为钢筋，以限制频繁维护的需要和相关的交通延误。尽管用这些合金增强的结构的寿命成本显著降低，但使用它们的最大障碍是初始成本。为了解决这个问题，钢铁公司正在开发具有较便宜合金成分的不锈钢牌号，但当局不愿意在打算使用75年或更长时间的结构中安装未经测试的合金。欧洲和北美的许多研究小组（包括申请人的）已经在短期实验室测试中研究了较新合金的相对腐蚀性能。然而，这些测试使用各种方法来加速腐蚀，通常包括最多三到五年的盐暴露，但有时短至3 - 4天。将加速试验的结果外推到真实的世界暴露3/4世纪留下了许多问题。 因此，为了更好地预测不锈钢和耐腐蚀增强合金的长期行为，拟议的研究计划的目标是确定它们嵌入混凝土并最终暴露于除冰盐时的冶金和电化学状态。在高pH环境中原位确定钝化膜的性质，有和没有氯化物，将是具有挑战性的，需要修改传统的方法。这项研究的另一个主要障碍将是在不从根本上改变条件的情况下实际实现这些高耐腐蚀合金的腐蚀。需要这些数据来确定它们的腐蚀速率。培训下一代工程师来实现这些突破性的进步是一个重要的成果。另一个是，这项研究的结果将允许基础设施设计师根据当地气候的严重程度和结构的预期使用寿命，为特定应用指定最具成本效益的材料。