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Title: Effect of Internal Curing as Mitigation to Minimize Alkali- Silica Reaction Damage

Author(s): Mengesha A. Beyene, Jose F. Munoz, Richard C. Meininger, and Carmelo Di Bella

Publication: Materials Journal

Volume: 114

Issue: 3

Appears on pages(s): 417-428

Keywords: alkali-silica reaction (ASR); capillary porosity; fluorescence microscopy; image analysis; internal curing (IC); lightweight aggregate (LWA); quantitative paste characterization; SEM-EDS; surface resistivity

Date: 5/1/2017

Abstract:
Internal curing can reduce alkali-silica reaction (ASR) damage in concrete. Alkali reactions with chert in natural sand caused damaging ASR in plain concrete. However, ASR damage was minimal in companion internally cured (IC) concrete in which a portion of the sand was replaced with pre-wetted lightweight aggregate (LWA). IC improved paste quality through a quantitative reduction in paste porosity and unhydrated cement. This was assessed using quantitative paste characterization including image analysis of backscattered electron (BSE) images, quantitative fluorescent intensity assessment, resistivity measurements, and qualitative analyses using SEM-EDS and polarized light microscopy. In concretes with the same water-cement ratio (w/c), IC concrete has denser paste microstructure from increased hydration due to additional water from pre-wetted LWA. Less permeable paste reduced fluid ingress, ASR reaction, and crack propagation. This demonstrates the potential of internal curing as a mitigation tool in reducing damage from ASR when high cement content and potentially reactive aggregates are used.




  

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