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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Title: Investigation of Reactivity of Fly Ash and Its Effect on Mixture Properties
Author(s): Deborah Glosser, Antara Choudhary, O. Burkan Isgor, and W. Jason Weiss
Publication: Materials Journal
Appears on pages(s): 193-200
Keywords: durability; fly ash; mixture proportioning; pozzolanicity; reactivity; supplementary cementitious material; thermodynamic modeling
Abstract:The reactivity of fly ash can vary considerably when used as a supplementary cementitious material (SCM). This paper demonstrates a framework for a standard test method to quantify the maximum reactivity of fly ash. The test is based on mixing reagent-grade calcium hydroxide (CH) and fly ash in a 3:1 mass ratio and exposing the mixture to 0.5 M potassium hydroxide (KOH) solution. Isothermal calorimetry and thermogravimetric analysis (TGA) are used to measure heat release and CH consumption, respectively, which are done in conjunction with thermodynamic calculations, as a basis to characterize the maximum reactivity of the fly ash. Fifteen fly ashes were tested using the method, which revealed that the reactivities ranged from 33 to 75%. Thermodynamic modeling was used to demonstrate the effect of fly ash reactivity on the properties of blended OPC-fly ash mixtures with different fly ash replacement levels (0 to 80%) and at various reactivities (0 to 100%). It was shown that the reactivity of fly ash is a critical factor determining durability-related parameters of mixtures such as CH content, C-S-H type and content, and the pH of the pore solution.
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