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

最近的两个新见解--发现水被紧紧地握在碱-硅胶(ASR)结构中，有助于其膨胀性，以及ASR诱导的膨胀率取决于ASR凝胶形成的位置(即，当凝胶体内形成凝胶时更大的膨胀)--表明现在有必要对ASR进行新的全面检查。这项多物理研究工作的主要目标是使人们对ASR的基本方面有新的了解，特别是要更好地了解ASR凝胶形成的位置和体积与凝胶的组成之间的关系，特别是水分和钙含量，以及对混凝土的潜在膨胀和损害。这一全面的努力是为了利用微波方法对水分含量和结合的敏感性以及非线性和线性声学方法对破裂的敏感性，以克服与现场检测水泥材料耐久性反应相关的一些挑战。将这些数据与多尺度结构、组成和力学性能的随时间变化相关联，将为对混凝土基础设施日益有害的反应带来新的见解。近年来，围绕混凝土ASR的长期技术信念受到越来越多的质疑，削弱了工程师评估骨料活性、设计抗ASR混凝土以及评估ASR在服役中损伤的可能性的能力。对混凝土中发生的渐进性ASR损伤的新理解将有助于改进混凝土设计以避免ASR，改进现场损伤监测，确定ASR损坏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之外，还将通过培训和指导佐治亚理工学院和密苏里科技大学不同的、多学科的研究生和本科生研究人员团队来产生影响。此外，PI和他们的学生将通过在其家庭校园建立的计划参与外展活动。

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.