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Title: Thaumasite formation in a tunnel of Bapanxia Dam in Western China

Abstract

A site investigation and sampling was carried out on a sulfate-attacked concrete structure in Bapanxia Hydraulic Power Plant in Western China. The concrete had been exposed to ground water containing substantial concentrations of salts (SO{sub 4} {sup 2-}, CO{sub 3} {sup 2-} and Cl{sup -}) for about 6 years and was analyzed with X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), laser-Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. It is shown that a white mushy mixture consisting of thaumasite, ettringite, gypsum and calcite is present in the residual concrete. This paper reports the first instance of the thaumasite form of sulfate attack of concrete in China.

Authors:
 [1];  [2];  [3];  [4]
  1. Key Laboratory of Silicate Materials Science and Engineering of Ministry of Education, Wuhan University of Technology, Wuhan 430070, (China)
  2. Key Laboratory of Silicate Materials Science and Engineering of Ministry of Education, Wuhan University of Technology, Wuhan 430070, (China). E-mail: xjgao2002@yahoo.com.cn
  3. CMRU, Department of Civil and Structural Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom)
  4. Department of Engineering Materials, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom)
Publication Date:
OSTI Identifier:
20793284
Resource Type:
Journal Article
Resource Relation:
Journal Name: Cement and Concrete Research; Journal Volume: 36; Journal Issue: 4; Other Information: DOI: 10.1016/j.cemconres.2005.10.011; PII: S0008-8846(05)00233-4; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CALCITE; CHINA; CONCRETES; DAMS; FOURIER TRANSFORMATION; GROUND WATER; GYPSUM; INFRARED SPECTRA; PYRAZOLINES; RAMAN SPECTROSCOPY; SCANNING ELECTRON MICROSCOPY; SULFATES; TUNNELS; X-RAY DIFFRACTION; X-RAY SPECTROSCOPY

Citation Formats

Ma Baoguo, Gao Xiaojian, Byars, Ewan A., and Zhou Qizhi. Thaumasite formation in a tunnel of Bapanxia Dam in Western China. United States: N. p., 2006. Web. doi:10.1016/J.CEMCONRES.2005.1.
Ma Baoguo, Gao Xiaojian, Byars, Ewan A., & Zhou Qizhi. Thaumasite formation in a tunnel of Bapanxia Dam in Western China. United States. doi:10.1016/J.CEMCONRES.2005.1.
Ma Baoguo, Gao Xiaojian, Byars, Ewan A., and Zhou Qizhi. Sat . "Thaumasite formation in a tunnel of Bapanxia Dam in Western China". United States. doi:10.1016/J.CEMCONRES.2005.1.
@article{osti_20793284,
title = {Thaumasite formation in a tunnel of Bapanxia Dam in Western China},
author = {Ma Baoguo and Gao Xiaojian and Byars, Ewan A. and Zhou Qizhi},
abstractNote = {A site investigation and sampling was carried out on a sulfate-attacked concrete structure in Bapanxia Hydraulic Power Plant in Western China. The concrete had been exposed to ground water containing substantial concentrations of salts (SO{sub 4} {sup 2-}, CO{sub 3} {sup 2-} and Cl{sup -}) for about 6 years and was analyzed with X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), laser-Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. It is shown that a white mushy mixture consisting of thaumasite, ettringite, gypsum and calcite is present in the residual concrete. This paper reports the first instance of the thaumasite form of sulfate attack of concrete in China.},
doi = {10.1016/J.CEMCONRES.2005.1},
journal = {Cement and Concrete Research},
number = 4,
volume = 36,
place = {United States},
year = {Sat Apr 15 00:00:00 EDT 2006},
month = {Sat Apr 15 00:00:00 EDT 2006}
}
  • According to microanalytical investigations, it is shown that the concrete of Yongan Dam is deteriorated due to the thaumasite form of sulfate attack (TSA). Analysis results of scanning electron microscopy (SEM), Energy Disperse X-ray (EDX) and X-ray Diffraction (XRD) are supported by the analysis of the concrete composition and the geographical conditions of the dam.
  • 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 themore » 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.« less
  • The formation of thaumasite was investigated with the progressive equilibrium approach (PEA). This approach experimentally simulates the conditions of various levels of sulfate addition in hardened cement pastes. The influence of limestone, time, C{sub 3}A content, temperature and leaching on thaumasite formation was investigated. The results show that thaumasite formation is favoured at lower temperatures (8 deg. C) independently of the type of cement clinker (high or low C{sub 3}A content) used. Thaumasite was found to form only in systems where limestone was present and where sufficient sulfate had been added. Thaumasite precipitated only in systems where the Al presentmore » has already been consumed to form ettringite and the molar SO{sub 3}/Al{sub 2}O{sub 3} ratio exceeded 3. In leached samples (reduction of portlandite and alkalis) slightly less thaumasite was formed whereas gypsum and ettringite are favoured under these conditions. The PEA, used to investigate the chemical aspects of sulfate attack was found to be a good tool for simulating external sulfate attack. Generally, thaumasite was detected were it was modelled to be stable in significant amounts. However, in this study equilibrium conditions were not reached after 9 months.« less
  • It has recently been derived by thermodynamic calculation that the presence or absence of calcium hydroxide plays a vital role in the resistance of cement paste or concrete against the formation of thaumasite. To obtain experimental data on this matter, special binders have been mixed and used for the preparation of mortar bars. These specimens were exposed to moderate sulphate attack for a period of 18 months at a temperature of 8 deg. C. Mortar bars containing calcium hydroxide showed visual signs of attack a few months after exposure, leading to expansion, mass loss and complete failure. In contrast tomore » this, no signs of attack were observed when no calcium hydroxide was present in the microstructure. These results confirm the conclusions of earlier thermodynamic calculations that the presence of calcium hydroxide has an important impact on the formation of thaumasite. Calcium-rich C-S-H formed in the presence of calcium hydroxide is vulnerable against sulphate attack and the formation of thaumasite. In the absence of calcium hydroxide, C-S-H has a much lower calcium/silicon ratio and a higher resistance against the formation of thaumasite.« less
  • Damages in concrete containing sulfide-bearing aggregates were recently observed in the Trois-Rivieres area (Quebec, Canada), characterized by rapid deterioration within 3 to 5 years after construction. A petrographic examination of concrete core samples was carried out using a combination of tools including: stereomicroscopic evaluation, polarized light microscopy, scanning electron microscopy, X-ray diffraction and electron microprobe analysis. The aggregate used to produce concrete was an intrusive igneous rock with different metamorphism degrees and various proportions of sulfide minerals. In the rock, sulfide minerals were often surrounded by a thin layer of carbonate minerals (siderite). Secondary reaction products observed in the damagedmore » concrete include 'rust' mineral forms (e.g. ferric oxyhydroxides such as goethite, limonite (FeO (OH) nH{sub 2}O) and ferrihydrite), gypsum, ettringite and thaumasite. In the presence of water and oxygen, pyrrhotite oxidizes to form iron oxyhydroxides and sulphuric acid. The acid then reacts with the phases of the cement paste/aggregate and provokes the formation of sulfate minerals. Understanding both mechanisms, oxidation and internal sulfate attack, is important to be able to duplicate the damaging reaction in laboratory conditions, thus allowing the development of a performance test for evaluating the potential for deleterious expansion in concrete associated with sulfide-bearing aggregates.« less