Collaborative Research: Understanding Fundamental Aspects of the Alkali Silica Reaction through Microwave and Acoustic Measurements

最近的两个新发现——水被紧紧地保持在碱-硅胶（ASR）结构中，有助于其膨胀，以及ASR诱导的膨胀率取决于ASR凝胶形成的位置（即，当凝胶在聚集体中形成时，膨胀更大）的建议——表明现在有必要对ASR进行更新和全面的检查。这项多物理场研究工作的总体目标是为ASR的基本方面带来新的认识，特别侧重于提高对ASR凝胶形成的位置和体积以及凝胶成分（特别是水分和钙含量）之间关系的理解，以及对混凝土膨胀和损伤的潜在影响。利用微波方法对含水率和结合度的敏感性，以及非线性和线性声学方法对开裂的敏感性，这一综合性的努力已经被开发出来，以克服与胶凝材料耐久性反应的现场检查相关的一些挑战。将这些数据与多尺度结构、成分和机械性能的随时间变化相关联，将为对混凝土基础设施造成日益严重破坏的反应带来新的见解。近年来，围绕混凝土中ASR的长期技术信念受到越来越多的质疑，这削弱了工程师评估骨料反应性、设计抗ASR混凝土以及评估使用中ASR损伤可能性的能力。对混凝土中发生的渐进式ASR损伤的新理解将允许改进混凝土设计以避免ASR，在损伤现场监测方面取得进展，确定ASR损伤结构的适当维护策略，并有助于提高使用寿命预测的准确性。除了改善混凝土耐久性对可持续发展的更广泛影响的贡献之外，还将通过对乔治亚理工学院和密苏里科技大学的研究生和本科生研究人员的多样化和多学科团队的培训和指导产生影响，计划向技术和非技术对象广泛传播研究成果。此外，这些学院及其学生还将通过在各自学校设立的项目参与外展活动。

Two new recent insights - the finding that water is tightly held in the alkali-silica gel (ASR) structure, contributing to its expansivity and the proposal that the rate of ASR-induced expansion depends upon the location of the ASR gel formation (i.e., greater expansion when gel forms within the aggregate) - suggest that a renewed and comprehensive examination of ASR is now warranted. The overarching objective of this multi-physics research effort is to bring new understanding to the fundamental aspects of ASR, with specific focus on improving understanding of the relationships between location and volume of ASR gel formation and the composition of the gel, particularly the moisture and calcium contents, on potential for expansion and damage to concrete. This comprehensive effort has been developed to take advantage of the sensitivity of microwave methods to moisture content and binding and the sensitivity of nonlinear and linear acoustic methods to cracking to overcome some of the challenges associated with the in situ examination of durability reactions in cementititious materials. Correlating these data with time-dependent changes in multi-scale structure, composition, and mechanical properties will bring new insight to a reaction which is increasingly damaging to concrete infrastructure.Long-held technical beliefs surrounding ASR in concrete have been increasingly questioned in recent years, undermining the ability of engineers to assess aggregate reactivity, to design ASR-resistant concrete, and to assess the potential for ASR damage in service. New understanding of the progressive ASR damage occurring in concrete will allow for improvements in concrete design to avoid ASR, advances in field monitoring of damage, identification of appropriate maintenance strategies for ASR-damaged structures, and contribute to improved accuracy in service life predictions. Beyond the contributions of improved concrete durability to the broader impact of sustainable development, impact will be made through training and mentoring of a diverse and multi-disciplinary team of graduate and undergraduate researchers at both Georgia Institute of Technology and Missouri University of Science and Technology Broad dissemination of research results to technical and non-technical audiences alike is planned. In addition, the PIs and their students will participate in outreach activities through programs established at their home campuses.