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Title: The C-S-H gel of Portland cement mortars: Part I. The interpretation of energy-dispersive X-ray microanalyses from scanning electron microscopy, with some observations on C-S-H, AFm and AFt phase compositions

Abstract

Scanning electron microscopy (SEM) microanalyses of the calcium-silicate-hydrate (C-S-H) gel in Portland cement pastes rarely represent single phases. Essential experimental requirements are summarised and new procedures for interpreting the data are described. These include, notably, plots of Si/Ca against other atom ratios, 3D plots to allow three such ratios to be correlated and solution of linear simultaneous equations to test and quantify hypotheses regarding the phases contributing to individual microanalyses. Application of these methods to the C-S-H gel of a 1-day-old mortar identified a phase with Al/Ca=0.67 and S/Ca=0.33, which we consider to be a highly substituted ettringite of probable composition C{sub 6}A{sub 2}S-bar{sub 2}H{sub 34} or {l_brace}Ca{sub 6}[Al(OH){sub 6}]{sub 2}{center_dot}24H{sub 2}O{r_brace}(SO{sub 4}){sub 2}[Al(OH){sub 4}]{sub 2}. If this is true for Portland cements in general, it might explain observed discrepancies between observed and calculated aluminate concentrations in the pore solution. The C-S-H gel of a similar mortar aged 600 days contained unsubstituted ettringite and an AFm phase with S/Ca=0.125.

Authors:
; ;
Publication Date:
OSTI Identifier:
20658326
Resource Type:
Journal Article
Journal Name:
Cement and Concrete Research
Additional Journal Information:
Journal Volume: 33; Journal Issue: 9; Other Information: DOI: 10.1016/S0008-8846(03)00064-4; PII: S0008884603000644; Copyright (c) 2003 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0008-8846
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINATES; CALCIUM SILICATES; GELS; HYDRATION; MORTARS; PORTLAND CEMENT; SCANNING ELECTRON MICROSCOPY; SULFATES; X RADIATION

Citation Formats

Famy, C, Brough, A R, and Taylor, H F W. The C-S-H gel of Portland cement mortars: Part I. The interpretation of energy-dispersive X-ray microanalyses from scanning electron microscopy, with some observations on C-S-H, AFm and AFt phase compositions. United States: N. p., 2003. Web. doi:10.1016/S0008-8846(03)00064-4.
Famy, C, Brough, A R, & Taylor, H F W. The C-S-H gel of Portland cement mortars: Part I. The interpretation of energy-dispersive X-ray microanalyses from scanning electron microscopy, with some observations on C-S-H, AFm and AFt phase compositions. United States. https://doi.org/10.1016/S0008-8846(03)00064-4
Famy, C, Brough, A R, and Taylor, H F W. 2003. "The C-S-H gel of Portland cement mortars: Part I. The interpretation of energy-dispersive X-ray microanalyses from scanning electron microscopy, with some observations on C-S-H, AFm and AFt phase compositions". United States. https://doi.org/10.1016/S0008-8846(03)00064-4.
@article{osti_20658326,
title = {The C-S-H gel of Portland cement mortars: Part I. The interpretation of energy-dispersive X-ray microanalyses from scanning electron microscopy, with some observations on C-S-H, AFm and AFt phase compositions},
author = {Famy, C and Brough, A R and Taylor, H F W},
abstractNote = {Scanning electron microscopy (SEM) microanalyses of the calcium-silicate-hydrate (C-S-H) gel in Portland cement pastes rarely represent single phases. Essential experimental requirements are summarised and new procedures for interpreting the data are described. These include, notably, plots of Si/Ca against other atom ratios, 3D plots to allow three such ratios to be correlated and solution of linear simultaneous equations to test and quantify hypotheses regarding the phases contributing to individual microanalyses. Application of these methods to the C-S-H gel of a 1-day-old mortar identified a phase with Al/Ca=0.67 and S/Ca=0.33, which we consider to be a highly substituted ettringite of probable composition C{sub 6}A{sub 2}S-bar{sub 2}H{sub 34} or {l_brace}Ca{sub 6}[Al(OH){sub 6}]{sub 2}{center_dot}24H{sub 2}O{r_brace}(SO{sub 4}){sub 2}[Al(OH){sub 4}]{sub 2}. If this is true for Portland cements in general, it might explain observed discrepancies between observed and calculated aluminate concentrations in the pore solution. The C-S-H gel of a similar mortar aged 600 days contained unsubstituted ettringite and an AFm phase with S/Ca=0.125.},
doi = {10.1016/S0008-8846(03)00064-4},
url = {https://www.osti.gov/biblio/20658326}, journal = {Cement and Concrete Research},
issn = {0008-8846},
number = 9,
volume = 33,
place = {United States},
year = {Mon Sep 01 00:00:00 EDT 2003},
month = {Mon Sep 01 00:00:00 EDT 2003}
}