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Title: A new quantification method based on SEM-EDS to assess fly ash composition and study the reaction of its individual components in hydrating cement paste

Calcareous fly ashes are high-potential reactive residues for blended cements, but their qualification and use in concrete are hindered by heterogeneity and variability. Current characterization often fails to identify the dominant, most reactive, amorphous fraction of the ashes. We developed an approach to characterize ashes using electron microscopy. EDS element composition of millions of points is plotted in a ternary frequency plot. A visual analysis reveals number and ranges of chemical composition of populations: silicate, calcium-silicate, aluminosilicate, and calcium-rich aluminosilicate. We quantified these populations in four ashes and followed their hydration in two Portland-ash systems. One ash reacted at a moderate rate: it was composed of 70 vol.% of aluminosilicates and calcium-silicates and reached 60% reaction at 90 days. The other reacted faster, reaching 60% at 28 days due to 55 vol.% of calcium-rich aluminosilicates, but further reaction was slower and 15 vol.% of phases, the silica-rich ones, did not react.
Authors:
 [1] ;  [1] ;  [2] ;  [1]
  1. Laboratory of Construction Materials, École Polytechnique Fédérale de Lausanne (EPFL), Station 12, CH-1015 Lausanne (Switzerland)
  2. HeidelbergCement Technology Center GmbH (HeidelbergCement AG), Rohrbacher Str. 95, 69181 Leimen (Germany)
Publication Date:
OSTI Identifier:
22475510
Resource Type:
Journal Article
Resource Relation:
Journal Name: Cement and Concrete Research; Journal Volume: 73; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINIUM SILICATES; AMORPHOUS STATE; CALCIUM SILICATES; CEMENTS; CHEMICAL COMPOSITION; CONCRETES; FLY ASH; HYDRATES; HYDRATION; IMAGE PROCESSING; MULTI-ELEMENT ANALYSIS; SCANNING ELECTRON MICROSCOPY; X-RAY SPECTROSCOPY