EAGER Collaborative Research: Development of Synthetic Fly Ash Glass as a Model System for Investigating Fly Ash Reactivity

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"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."The objective of this EAGER research is to demonstrate the feasibility of using synthetic fly ash glass as a model for systematic studies of fly ash reactivity instead of using real fly ash. It will demonstrate that synthetic fly ash specimens will produce reactivity data consistent with that of actual fly ashes, while at the same time enabling the use of analytical methods that cannot be used on the latter. This will establish the basis for future systematic studies of fly ash reactivity. In this proposed research, several fly ash glasses will be prepared with compositions based on those of characteristic clusters identified in real fly ash. Powdered glass samples will be hydrated in parallel with whole fly ash specimens and analyzed. In addition synthetic glass monoliths with typical dimensions of 1 cm will be hydrated in individual Teflon containers. This approach enables quantitative determination by mass balances of the glass leach rates as a function of solution chemistry and glass composition. It also permits the subsequent detailed analysis of the gel layer using SEM and micro-Raman analysis. This is not feasible for whole fly ashes.This research effort will help accelerate the usage of fly ash by the concrete industry through an improved understanding of fundamental factors controlling reactivity. This will lead to the better prediction of fly ash glass behavior in cement paste based on its reactivity instead of trial and error by conventional tests. This in turn will lead to a more effective use of fly ash, which will increase the utilization rate and provide economical use of a waste material and lower emissions of CO2.