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Alkali–Silica Reaction: the Influence of Calcium on Silica Dissolution and the Formation of Reaction Products
Author(s) -
Leemann Andreas,
Le Saout Gwenn,
Winnefeld Frank,
Rentsch Daniel,
Lothenbach Barbara
Publication year - 2011
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2010.04202.x
Subject(s) - portlandite , dissolution , alkali–silica reaction , chemistry , thermogravimetric analysis , alkali metal , desorption , inorganic chemistry , chemical engineering , materials science , portland cement , cement , organic chemistry , adsorption , metallurgy , engineering
In a model system for alkali–silica reaction consisting of microsilica, portlandite (0–40 mass%), and 1 M alkaline solutions (NaOH, KOH), the influence of calcium on silica dissolution and on the formation of reaction products is investigated. The reaction and its products are characterized using calorimetry, X‐ray diffraction, thermogravimetric analysis, nuclear magnetic resonance, desorption experiments, and pore solution analysis in combination with thermodynamic modeling. Silica dissolution proceeds until portlandite is consumed due to the formation of C–S–H, and subsequently, saturation of dissolved silica in the alkaline solution is reached. As a result, the amount of dissolved silica increases with the increasing portlandite content. Depending on the amount of portlandite added, the reaction products show differences in the relative amounts of Q 1 , Q 2 , and Q 3 sites formed and in their average Ca/Si ratio. The ability of the reactions products to chemically bind water decreases with the decreasing relative amount of Q 3 sites and with the increasing Ca/Si ratio. However, the amount of physically bound water in the reaction products reaches a maximum value at a Ca/Si ratio between 0.20 and 0.30.