22 Downloads (Pure)

Abstract

The exchange of ions during the dissolution of Portlandite and precipitation of newly formed carbonate phases, at the beginning of the carbonation reaction has been investigated. Changes in the isotopic composition of carbonates was determined using Time-of-Flight-Secondary Ion Mass Spectrometry and Raman spectroscopy. Samples of pure Ca(18OH)2 were carbonated in humid air (containing almost exclusively 16O) and characterized using Scanning Electron Microscopy and Raman Spectroscopy, aided by Density Functional Theory calculations. Results show that the carbonation process at high pH (i.e. >12) is a two-stage mechanism. The first stage occurs over a short period of time after the Ca(18OH)2 is exposed to air and involves the dissolution of surface Ca2+ ions and hydroxyl 18OH- groups. The latter react directly with the dissolved CO2, leading to the formation of C18O16O22- ions containing 1/3 of 18O. Since this ion is the precursor of the newly formed carbonate phases, a similar oxygen content was found in the precipitates. The 18O:16O ratio of 1:2 in the carbonates at the beginning of the reaction is in agreement with a carbonation model proposed by Létolle and colleagues in 1990 [1] describing a direct reaction of CO2 with the OH- groups produced by the dissociation of water. The second stage of the reaction occurs within 24 hours of exposure to air and involves a rebalance of the oxygen isotopic composition in the carbonate phases with a higher concentration of 16O.
Original languageEnglish
Pages199-202
Publication statusPublished - 11 Sep 2017
Event37th Cement and Concrete Science Conference - UCL, London, UK United Kingdom
Duration: 11 Sep 201712 Sep 2017
http://www.ucl.ac.uk/aim/conference-info/37ccs

Conference

Conference37th Cement and Concrete Science Conference
Abbreviated title37th CCS Conference
CountryUK United Kingdom
CityLondon
Period11/09/1712/09/17
Internet address

Fingerprint

Carbonation
Carbonates
Ion exchange
Phase transitions
Ions
Raman spectroscopy
Dissolution
Air
Oxygen
Secondary ion mass spectrometry
Chemical analysis
Density functional theory
Precipitates
Scanning electron microscopy
Water

Cite this

Pesce, G., Fletcher, I., Grant, R., Parker, S., Molinari, M., & Ball, R. (2017). Phase Transformations and Ion Exchange During Early Age Carbonation. 199-202. Paper presented at 37th Cement and Concrete Science Conference, London, UK United Kingdom.

Phase Transformations and Ion Exchange During Early Age Carbonation. / Pesce, Giovanni; Fletcher, Ian; Grant, Robert; Parker, Stephen; Molinari, Marco; Ball, Richard.

2017. 199-202 Paper presented at 37th Cement and Concrete Science Conference, London, UK United Kingdom.

Research output: Contribution to conferencePaper

Pesce, G, Fletcher, I, Grant, R, Parker, S, Molinari, M & Ball, R 2017, 'Phase Transformations and Ion Exchange During Early Age Carbonation' Paper presented at 37th Cement and Concrete Science Conference, London, UK United Kingdom, 11/09/17 - 12/09/17, pp. 199-202.
Pesce G, Fletcher I, Grant R, Parker S, Molinari M, Ball R. Phase Transformations and Ion Exchange During Early Age Carbonation. 2017. Paper presented at 37th Cement and Concrete Science Conference, London, UK United Kingdom.
Pesce, Giovanni ; Fletcher, Ian ; Grant, Robert ; Parker, Stephen ; Molinari, Marco ; Ball, Richard. / Phase Transformations and Ion Exchange During Early Age Carbonation. Paper presented at 37th Cement and Concrete Science Conference, London, UK United Kingdom.
@conference{37812b70b3274837901e9e4870688440,
title = "Phase Transformations and Ion Exchange During Early Age Carbonation",
abstract = "The exchange of ions during the dissolution of Portlandite and precipitation of newly formed carbonate phases, at the beginning of the carbonation reaction has been investigated. Changes in the isotopic composition of carbonates was determined using Time-of-Flight-Secondary Ion Mass Spectrometry and Raman spectroscopy. Samples of pure Ca(18OH)2 were carbonated in humid air (containing almost exclusively 16O) and characterized using Scanning Electron Microscopy and Raman Spectroscopy, aided by Density Functional Theory calculations. Results show that the carbonation process at high pH (i.e. >12) is a two-stage mechanism. The first stage occurs over a short period of time after the Ca(18OH)2 is exposed to air and involves the dissolution of surface Ca2+ ions and hydroxyl 18OH- groups. The latter react directly with the dissolved CO2, leading to the formation of C18O16O22- ions containing 1/3 of 18O. Since this ion is the precursor of the newly formed carbonate phases, a similar oxygen content was found in the precipitates. The 18O:16O ratio of 1:2 in the carbonates at the beginning of the reaction is in agreement with a carbonation model proposed by L{\'e}tolle and colleagues in 1990 [1] describing a direct reaction of CO2 with the OH- groups produced by the dissociation of water. The second stage of the reaction occurs within 24 hours of exposure to air and involves a rebalance of the oxygen isotopic composition in the carbonate phases with a higher concentration of 16O.",
author = "Giovanni Pesce and Ian Fletcher and Robert Grant and Stephen Parker and Marco Molinari and Richard Ball",
year = "2017",
month = "9",
day = "11",
language = "English",
pages = "199--202",
note = "37th Cement and Concrete Science Conference, 37th CCS Conference ; Conference date: 11-09-2017 Through 12-09-2017",
url = "http://www.ucl.ac.uk/aim/conference-info/37ccs",

}

TY - CONF

T1 - Phase Transformations and Ion Exchange During Early Age Carbonation

AU - Pesce, Giovanni

AU - Fletcher, Ian

AU - Grant, Robert

AU - Parker, Stephen

AU - Molinari, Marco

AU - Ball, Richard

PY - 2017/9/11

Y1 - 2017/9/11

N2 - The exchange of ions during the dissolution of Portlandite and precipitation of newly formed carbonate phases, at the beginning of the carbonation reaction has been investigated. Changes in the isotopic composition of carbonates was determined using Time-of-Flight-Secondary Ion Mass Spectrometry and Raman spectroscopy. Samples of pure Ca(18OH)2 were carbonated in humid air (containing almost exclusively 16O) and characterized using Scanning Electron Microscopy and Raman Spectroscopy, aided by Density Functional Theory calculations. Results show that the carbonation process at high pH (i.e. >12) is a two-stage mechanism. The first stage occurs over a short period of time after the Ca(18OH)2 is exposed to air and involves the dissolution of surface Ca2+ ions and hydroxyl 18OH- groups. The latter react directly with the dissolved CO2, leading to the formation of C18O16O22- ions containing 1/3 of 18O. Since this ion is the precursor of the newly formed carbonate phases, a similar oxygen content was found in the precipitates. The 18O:16O ratio of 1:2 in the carbonates at the beginning of the reaction is in agreement with a carbonation model proposed by Létolle and colleagues in 1990 [1] describing a direct reaction of CO2 with the OH- groups produced by the dissociation of water. The second stage of the reaction occurs within 24 hours of exposure to air and involves a rebalance of the oxygen isotopic composition in the carbonate phases with a higher concentration of 16O.

AB - The exchange of ions during the dissolution of Portlandite and precipitation of newly formed carbonate phases, at the beginning of the carbonation reaction has been investigated. Changes in the isotopic composition of carbonates was determined using Time-of-Flight-Secondary Ion Mass Spectrometry and Raman spectroscopy. Samples of pure Ca(18OH)2 were carbonated in humid air (containing almost exclusively 16O) and characterized using Scanning Electron Microscopy and Raman Spectroscopy, aided by Density Functional Theory calculations. Results show that the carbonation process at high pH (i.e. >12) is a two-stage mechanism. The first stage occurs over a short period of time after the Ca(18OH)2 is exposed to air and involves the dissolution of surface Ca2+ ions and hydroxyl 18OH- groups. The latter react directly with the dissolved CO2, leading to the formation of C18O16O22- ions containing 1/3 of 18O. Since this ion is the precursor of the newly formed carbonate phases, a similar oxygen content was found in the precipitates. The 18O:16O ratio of 1:2 in the carbonates at the beginning of the reaction is in agreement with a carbonation model proposed by Létolle and colleagues in 1990 [1] describing a direct reaction of CO2 with the OH- groups produced by the dissociation of water. The second stage of the reaction occurs within 24 hours of exposure to air and involves a rebalance of the oxygen isotopic composition in the carbonate phases with a higher concentration of 16O.

M3 - Paper

SP - 199

EP - 202

ER -