Environmental controls and reaction pathways of coupled de-dolomitization and thaumasite formation

Abstract

Deteriorated concrete and interstitial solutions (IS) were collected from Austrian tunnels to elucidate potential connections between de-dolomitization caused by coupled alkali carbonate reactions (ACR) and thaumasite form of sulfate attack (TSA). A conceptual reaction model for the portlandite-CSH phases-dolomite-calcium sulfate-calcite-brucite-thaumasite system was developed based on experimental data, hydrochemical modelling, IS chemistry and apparent concrete compositions. During the initial stage of sulfate attack, ettringite and gypsum formation weakened the concrete's microstructure and initiated ACR Leaching of hydrated cement phases resulted in IS with a pH similar to 12-13, which promoted incongruent dolomite dissolution. Infiltration of Ca-SO4-type ground water into the de-dolomitization zone facilitated calcite and brucite neo-formations at 13 > pH > 10.5 during advanced states of concrete deterioration and subsequently resulted in thaumasite precipitation at pH similar to 8.7. In this contribution, the reaction mechanisms and environmental controls of de-dolomitization are discussed in relation to the durability of concrete under sulfate attack. (C) 2017 Elsevier Ltd. All rights reserved.

Keywords

Dolomite; Degradation; Sulfate attack; Pore solution; FIB-SEM; Alkali-Aggregate Reaction

Published in

Cement and Concrete Research
2017, Volume: 95, pages: 282-293 Publisher: PERGAMON-ELSEVIER SCIENCE LTD

SLU Authors

• Köhler, Stephan

  • Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Geochemistry


Publication identifier

DOI: https://doi.org/10.1016/j.cemconres.2017.02.011

Permanent link to this page (URI)

https://res.slu.se/id/publ/83029