TY - JOUR
T1 - Environmental controls and reaction pathways of coupled de-dolomitization and thaumasite formation
AU - Mittermayr, Florian
AU - Baldermann, Andre
AU - Baldermann, Claudia
AU - Grathoff, G.H.
AU - Klammer, Dietmar
AU - Köhler, Stephan Jürgen
AU - Leis, Albrecht
AU - Warr, Laurence
AU - Dietzel, Martin
PY - 2017
Y1 - 2017
N2 - 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 ~ 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 ~ 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.
AB - 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 ~ 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 ~ 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.
U2 - 10.1016/j.cemconres.2017.02.011
DO - 10.1016/j.cemconres.2017.02.011
M3 - Article
SN - 1873-3948
VL - 95
SP - 282
EP - 293
JO - Cement and Concrete Research
JF - Cement and Concrete Research
ER -