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

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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.