Investigating the feasibility of using reclaimed and remediated fly ashes as Class F fly ash alternatives

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Title: Investigating the feasibility of using reclaimed and remediated fly ashes as Class F fly ash alternatives

Author(s): Raissa Ferron, Ryan Kalina, Saif Al-Shmaisani, Maria Juenger

Publication: Special Publication

Volume: 320

Issue:

Appears on pages(s): 33.1-33.14

Keywords: supplementary cementitious materials; coal combustion residuals, reclaimed fly ash, remediated fly ash, compressive strength, durability, alkali-silica reaction

Date: 8/1/2017

Abstract:
Supplementary cementitious materials (SCMs) are a staple in modern day concrete. In the US, Class F fly ash is a preferred SCM due to its wide availability, low cost and beneficial effects on concrete’s mechanical properties, heat of hydration, durability performance, economics, and environmental performance. However, the quantity and quality of Class F fly ash is declining across many regions of the US. This paper presents the results of ongoing research that is being conducted to determine whether alternative ashes, specifically previously rejected coal combustion residuals and reclaimed coal combustion residuals, can be used to replace Class F fly ash in portland cement mixtures. The effects of these potential alternative binder materials on compressive strength and alkali-silica resistance are presented, as well as a discussion on the underlying mechanisms responsible for differences in the fly ash performance. The results indicate that beneficial effects of using reclaimed and remediated ashes on compressive strength are more pronounced at later time frames than at earlier time periods. Additionally, improvements in alkali-silica resistance can occur when suitable alternative ashes are used as cement replacements.