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Title: Prevention of thaumasite formation in concrete exposed to sulphate attack

Abstract

Thermodynamic calculations were performed to investigate at which sulphate ion concentration hardened concrete can be damaged by the formation of thaumasite. It is indicated that thaumasite can be formed from C-S-H phases and portlandite at very low sulphate concentrations in an aggressive solution. Higher sulphate ion concentrations are required in the absence of portlandite. Still higher sulphate ion concentrations are needed if C-S-H phases with a low calcium/silicon ratio are consumed. Therefore, it is suggested that the formation of thaumasite at low and moderate sulphate concentrations in the attacking solution can be avoided by lowering the calcium/silicon ratio in the C-S-H phases. This can be achieved by the addition of pozzolanic and latently hydraulic admixtures. During the reaction of these materials, portlandite is consumed and the calcium/silicon ratio of the C-S-H phases is lowered. The aforementioned concept was confirmed by studies published in the literature and also by experimental investigations reported in this paper.

Authors:
 [1];  [2]
  1. Institute for Building Materials Science, Department of Civil Engineering, Bauhaus-University Weimar Coudraystrasse 11, 99423 Weimar (Germany), E-mail: frank.bellmann@bauing.uni-weimar.de
  2. Institute for Building Materials Science, Department of Civil Engineering, Bauhaus-University Weimar Coudraystrasse 11, 99423 Weimar (Germany)
Publication Date:
OSTI Identifier:
21033059
Resource Type:
Journal Article
Journal Name:
Cement and Concrete Research
Additional Journal Information:
Journal Volume: 37; Journal Issue: 8; Other Information: DOI: 10.1016/j.cemconres.2007.04.007; PII: S0008-8846(07)00096-8; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0008-8846
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CALCIUM; CONCRETES; MOLECULAR IONS; SILICON; SULFATES

Citation Formats

Bellmann, F., and Stark, J.. Prevention of thaumasite formation in concrete exposed to sulphate attack. United States: N. p., 2007. Web. doi:10.1016/j.cemconres.2007.04.007.
Bellmann, F., & Stark, J.. Prevention of thaumasite formation in concrete exposed to sulphate attack. United States. doi:10.1016/j.cemconres.2007.04.007.
Bellmann, F., and Stark, J.. Wed . "Prevention of thaumasite formation in concrete exposed to sulphate attack". United States. doi:10.1016/j.cemconres.2007.04.007.
@article{osti_21033059,
title = {Prevention of thaumasite formation in concrete exposed to sulphate attack},
author = {Bellmann, F. and Stark, J.},
abstractNote = {Thermodynamic calculations were performed to investigate at which sulphate ion concentration hardened concrete can be damaged by the formation of thaumasite. It is indicated that thaumasite can be formed from C-S-H phases and portlandite at very low sulphate concentrations in an aggressive solution. Higher sulphate ion concentrations are required in the absence of portlandite. Still higher sulphate ion concentrations are needed if C-S-H phases with a low calcium/silicon ratio are consumed. Therefore, it is suggested that the formation of thaumasite at low and moderate sulphate concentrations in the attacking solution can be avoided by lowering the calcium/silicon ratio in the C-S-H phases. This can be achieved by the addition of pozzolanic and latently hydraulic admixtures. During the reaction of these materials, portlandite is consumed and the calcium/silicon ratio of the C-S-H phases is lowered. The aforementioned concept was confirmed by studies published in the literature and also by experimental investigations reported in this paper.},
doi = {10.1016/j.cemconres.2007.04.007},
journal = {Cement and Concrete Research},
issn = {0008-8846},
number = 8,
volume = 37,
place = {United States},
year = {2007},
month = {8}
}