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Title: A thermodynamic and kinetic model for paste–aggregate interactions and the alkali–silica reaction

A new conceptual model is developed for ASR formation based on geochemical principles tied to aqueous speciation, silica solubility, kinetically controlled mineral dissolution, and diffusion. ASR development is driven largely by pH and silica gradients that establish geochemical microenvironments between paste and aggregate, with gradients the strongest within the aggregate adjacent to the paste boundary (i.e., where ASR initially forms). Super-saturation of magadiite and okenite (crystalline ASR surrogates) occurs in the zone defined by gradients in pH, dissolved silica, Na +, and Ca 2+. This model provides a thermodynamic rather than kinetic explanation of why quartz generally behaves differently from amorphous silica: quartz solubility does not produce sufficiently high concentrations of H 4SiO 4 to super-saturate magadiite, whereas amorphous silica does. The model also explains why pozzolans do not generate ASR: their fine-grained character precludes formation of chemical gradients. Finally, these gradients have interesting implications beyond the development of ASR, creating unique biogeochemical environments.
Authors:
 [1] ; ORCiD logo [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Report Number(s):
LA-UR-14-29624
Journal ID: ISSN 0008-8846
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Cement and Concrete Research
Additional Journal Information:
Journal Volume: 76; Journal Issue: C; Journal ID: ISSN 0008-8846
Publisher:
Elsevier
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Fossil Energy (FE), Clean Coal and Carbon (FE-20)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 36 MATERIALS SCIENCE; Energy Sciences; pH gradient; alkali-­aggregate reaction; diffusion; modeling
OSTI Identifier:
1471335
Alternate Identifier(s):
OSTI ID: 1246650

Guthrie, George Drake Jr., and Carey, James William. A thermodynamic and kinetic model for paste–aggregate interactions and the alkali–silica reaction. United States: N. p., Web. doi:10.1016/j.cemconres.2015.05.004.
Guthrie, George Drake Jr., & Carey, James William. A thermodynamic and kinetic model for paste–aggregate interactions and the alkali–silica reaction. United States. doi:10.1016/j.cemconres.2015.05.004.
Guthrie, George Drake Jr., and Carey, James William. 2015. "A thermodynamic and kinetic model for paste–aggregate interactions and the alkali–silica reaction". United States. doi:10.1016/j.cemconres.2015.05.004. https://www.osti.gov/servlets/purl/1471335.
@article{osti_1471335,
title = {A thermodynamic and kinetic model for paste–aggregate interactions and the alkali–silica reaction},
author = {Guthrie, George Drake Jr. and Carey, James William},
abstractNote = {A new conceptual model is developed for ASR formation based on geochemical principles tied to aqueous speciation, silica solubility, kinetically controlled mineral dissolution, and diffusion. ASR development is driven largely by pH and silica gradients that establish geochemical microenvironments between paste and aggregate, with gradients the strongest within the aggregate adjacent to the paste boundary (i.e., where ASR initially forms). Super-saturation of magadiite and okenite (crystalline ASR surrogates) occurs in the zone defined by gradients in pH, dissolved silica, Na+, and Ca2+. This model provides a thermodynamic rather than kinetic explanation of why quartz generally behaves differently from amorphous silica: quartz solubility does not produce sufficiently high concentrations of H4SiO4 to super-saturate magadiite, whereas amorphous silica does. The model also explains why pozzolans do not generate ASR: their fine-grained character precludes formation of chemical gradients. Finally, these gradients have interesting implications beyond the development of ASR, creating unique biogeochemical environments.},
doi = {10.1016/j.cemconres.2015.05.004},
journal = {Cement and Concrete Research},
number = C,
volume = 76,
place = {United States},
year = {2015},
month = {5}
}