Reactivity Indicators for Activated High-Calcium Fly Ash-Based Binders

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Title: Reactivity Indicators for Activated High-Calcium Fly Ash-Based Binders

Author(s): E. Ivan Diaz Loya, Fred Kinney and Carlos Augusto Orozco Rios

Publication: Special Publication

Volume: 294

Issue:

Appears on pages(s): 1-22

Keywords: Class C fly ash, fly ash, activation, concrete, green cement, alternative binders, activated pozzolans.

Date: 10/4/2013

Abstract:
Over the last few decades there has been an increasing interest in low-carbon-foot-print binders that can replace hydraulic cement in concrete mixtures. Given that hydraulic cement is so ingrained in the building materials industry, alternative binders –in addition to offering a low carbon footprint– must exhibit similar or improved consistency and properties in a cost effective manner. A candidate that meets these criteria is activated high-calcium fly ash (AHCFA), which as the name implies uses high-calcium fly ash (HCFA) as main reactive powder along with an activator to increase its hydraulic activity and a setting retarder to regulate the rate of reaction. It is an attempt to get a better understanding of the factors that have greater influence in the reactivity of HCFA. The physical, chemical and crystallographic characterization as well as glass fragility analyses of several HCFA samples was paralleled with the compressive strength of their corresponding AHCFA mortars. Correlations between HCFA characteristics and the compressive strength of the resulting AHCFA mortars were sought. The results suggest that the reactivity of HCFA can be evaluated in terms of glass fragility using non-bridging oxygens per tetrahedron (NBO/T) and alumina saturation index (ASI) as main parameters.