Avoiding & mitigating alkali-aggregate reaction (AAR) in concrete structures

碱骨料反应（AAR）是影响加拿大乃至世界范围内混凝土基础设施耐久性的主要过程之一。多年来，世界各地已经开发了几种方法和建议，包括各种实验室测试程序，以评估混凝土骨料的潜在碱反应性和预防措施的有效性（例如控制水泥和混凝土碱含量，使用补充胶凝材料等），然后再在现场使用。尽管某些测试程序存在一些问题（例如，长期持续时间，碱浸，与现场结构的长期相关性，混凝土混合物的评估等），并且不断需要改进各种标准/协议，但大多数专家一致认为，总的来说，现在可以建造新的混凝土基础设施，其AAR风险最小，甚至可以计算/有限。然而，对于应该实施的最有效的方法（例如，控制水分的表面处理、化学处理、加强、应力消除等），以及何时修复受aar影响的混凝土结构/结构构件，目前还没有达成共识。在这种背景下，全球各地的许多工程师和研究人员一直在努力开发评估技术和工具，这些技术和工具能够阻止/减轻服役中AAR的进一步发展，或者至少评估受影响老化结构的当前损伤程度（诊断）和未来潜在的困境（预测）。这是为受AAR影响的关键老化基础设施选择有效修复方法和最佳使用周期的重要步骤。在此背景下，该研究项目与Kryton合作，旨在评估现有的商业产品并开发新产品，以防止和/或减轻（即物理，化学或两者）由AAR引起的混凝土在初期，中期和后期阶段的恶化。通过评估/开发当前/新产品来避免和减轻现场的AAR，这种CRD的科学效益非常明显。此外，Kryton将受益于与渥太华大学研究人员的合作和交流，以评估，开发和实施加拿大和全球土木工程市场的新产品。**

Alkali-aggregate reaction (AAR) is one of the main processes affecting the durability of concrete infrastructure in Canada and worldwide. Over the years, several approaches and recommendations, including a comprehensive variety of laboratory test procedures, have been developed around the world to assess the potential alkali-reactivity of concrete aggregates and the effectiveness of preventive measures (e.g. control of the cement & concrete alkali content, use of supplementary cementing materials, etc.) before their use in the field. Despite some issues with some test procedures (e.g. long-term duration, alkali leaching, long-term correlation with field structures, evaluation of concrete mixtures, etc.) and the constant need for improvement in the various standards/protocols, the majority of experts agree that, in general, it is now possible to build new concrete infrastructure with minimum or even calculated/limited risk of AAR. However, there is currently no consensus about the most efficient method(s) (e.g. surface treatments for moisture control, chemical treatments, strengthening, stress relief, etc.) that should be implemented, and when, for the rehabilitation of AAR-affected concrete structures/structural members. In this context, a number of engineers and researchers around the globe have been trying to develop appraisal techniques and tools that are capable of either halting/mitigating further AAR development in service or at least appraising the current damage degree (diagnosis) and the potential of future distress (prognosis) of affected aging structures, both essential steps in selecting efficient rehabilitation methods and optimum application periods for critical aging infrastructure affected by AAR. In this context, this research project, in collaboration with Kryton, aims to evaluate existing commercial products and develop new product(s) for preventing and/or mitigating (i.e. physically, chemically or both) concrete deterioration caused by AAR in its initial, moderate and advanced phases. The scientific benefit of this CRD is very clear through the evaluation/development of current/new products for avoiding & mitigating AAR in the field. Moreover, Kryton will benefit from the collaboration and exchange with uOttawa researchers to appraise, develop and implement new products to the Canadian and global civil engineering market. **