International RILEM Workshop on Internal Sulfate attack and Delayed Ettringite Formation

2004 ◽  
Vol 37 (1) ◽  
pp. 71-72 ◽  
Author(s):  
K. Scrivener ◽  
J. Skalny
Keyword(s):  
Sulfate Attack ◽  
Delayed Ettringite Formation ◽  
Ettringite Formation ◽  
Internal Sulfate Attack

The Development of Accelerated Test Method for Internal Sulfate Attack by Delayed Ettringite Formation

2020 ◽  
Vol 987 ◽  
pp. 27-32
Author(s):  
Van Huong Nguyen ◽  
Nordine Leklou ◽  
Pierre Mounanga
Keyword(s):  
Elevated Temperature ◽  
Electrochemical Techniques ◽  
Sulfate Attack ◽  
Test Method ◽  
Delayed Ettringite Formation ◽  
Ettringite Formation ◽  
Physico Chemical ◽  
Mechanical Performances ◽  
Induced Decomposition ◽  
Internal Sulfate Attack

Delayed Ettringite Formation (DEF) is an internal sulfate attack caused by heat-induced decomposition and/or prevention of normal ettringite formed during the initial hydration of cement at elevated temperature (above about 70°C) and its re-crystallization in the hardened matrix. This reaction is a physico-chemical phenomenon inducing an expansion of the cement paste that could lead to cracking of cementitious matrix. These cracks result in a decrease in the mechanical performances and durability parameters of the material. However, the internal sulfate attack is characterized by a very slow reaction kinetics and therefore it is difficult to study it in laboratories. This research developed an accelerated method focused on mortar specimens; it is based on electrochemical techniques in order to speed the leaching of alkalis that could be accelerated the DEF.

scholarly journals Pore size analyses of cement paste exposed to external sulfate attack and delayed ettringite formation

2019 ◽  
Vol 123 ◽  
pp. 105766 ◽  
Author(s):  
Yushan Gu ◽  
Renaud-Pierre Martin ◽  
Othman Omikrine Metalssi ◽  
Teddy Fen-Chong ◽  
Patrick Dangla
Keyword(s):  
Pore Size ◽  
Cement Paste ◽  
Sulfate Attack ◽  
Delayed Ettringite Formation ◽  
Ettringite Formation

scholarly journals Fractal Cracking Patterns in Concretes Exposed to Sulfate Attack

Materials ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2338 ◽  
Author(s):  
Jinwei Yao ◽  
Jiankang Chen ◽  
Chunsheng Lu
Keyword(s):  
Crack Nucleation ◽  
Fractal Dimensions ◽  
Sulfate Attack ◽  
Growth Patterns ◽  
X Ray Diffraction ◽  
Delayed Ettringite Formation ◽  
Crack Evolution ◽  
X Ray ◽  
Surface Cracking ◽  
Ettringite Formation

Sulfate attack tests were performed on concrete samples with three water-to-cement ratios, and micro-crack growth patterns on concrete surfaces were recorded. The expansive stress and crack nucleation caused by delayed ettringite formation (DEF) were studied using X-ray diffraction and scanning electron microscopy. By means of a digital image processing technology, fractal dimensions of surface cracking patterns were determined, which monotonously increase during corrosion. Moreover, it is shown that the change of fractal dimensions is directly proportional to accumulation of DEF, and therefore, a simple theoretical model could be proposed to describe the micro-crack evolution in concretes under sulfate attack.

scholarly journals Deterioration Caused By Sulfide-Bearing Aggregates: Performance Test Development

2021 ◽  
Author(s):  
Bradley Maguire
Keyword(s):  
Performance Test ◽  
Iron Sulfide ◽  
Coarse Aggregate ◽  
Test Methods ◽  
Sulfate Attack ◽  
Ettringite Formation ◽  
Heating And Cooling ◽  
Friedel’S Salt ◽  
Lime Solution ◽  
Internal Sulfate Attack

Recently in Quebec Canada, concrete structures suffered very rapid deterioration within 3 to 5 years of construction. The deterioration was caused by an iron sulfide, namely pyrrhotite, in the coarse aggregate that suffered oxidation inside concrete and promoted sulfate attack; indicated by the presence of ferric oxyhydroxides (“rust”), gypsum, ettringite, and thaumasite. The goal of the current work was to reproduce this reaction under accelerated laboratory conditions, in progression of a performance test. Conditions to promote pyrrhotite oxidation and internal sulfate attack were provided; exposure cycles were tested with heating and cooling, and saturation in oxidizing agents or lime solution. Oxidation was induced in concrete samples, however, other mechanisms contributed to deterioration. The bleach was found to promote NaCl and Friedel’s salt formation, furthermore, it seemed to mitigate expansion from sulfate attack. Sulfoaluminate decomposition was also found to cause secondary ettringite formation. More optimization to the test methods was recommended.

scholarly journals Valorization of Fine Recycled Aggregates Contaminated with Gypsum Residues: Characterization and Evaluation of the Risk for Secondary Ettringite Formation

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4866
Author(s):  
Charlotte Colman ◽  
David Bulteel ◽  
Sébastien Rémond ◽  
Zengfeng Zhao ◽  
Luc Courard
Keyword(s):  
Sulfate Attack ◽  
Recycled Aggregates ◽  
European Standard ◽  
Sulfate Content ◽  
Ettringite Formation ◽  
Comparison Results ◽  
Elevated Water ◽  
Contamination Levels ◽  
Mechanical Performances ◽  
Internal Sulfate Attack

Fine recycled aggregates (FRA) (0/4 mm) are up to now not valorized on a high enough level because of characteristics like an elevated water absorption, higher fines content, and the presence of contaminations. Leftover gypsum residues from the construction site can cause internal sulfate attack when FRA are incorporated into new structures. Concern about this deteriorating reaction plays an important role in the rejection of FRA. In this study, samples of FRA from different recycling centers were characterized and incorporated into mortars. They were then subjected to swelling tests in order to evaluate the development of sulfate attack. Reference materials with different amounts of sulfates were used as a comparison. Results showed a variable sulfate content in industrial FRA, depending heavily on the source of the materials. In all but one case, the total amounts surpassed the acceptable sulfate contents specified in the European standard EN 206, meaning the FRA would be rejected for reuse in concrete. Nevertheless, swelling tests demonstrated that these contamination levels did not pose a risk for sulfate attack. These results indicated that the incorporation of FRA leads to acceptable mechanical performances and that the sulfate limit could be reviewed to be less strict.

scholarly journals Deterioration Caused By Sulfide-Bearing Aggregates: Performance Test Development

2021 ◽  
Author(s):  
Bradley Maguire
Keyword(s):  
Performance Test ◽  
Iron Sulfide ◽  
Coarse Aggregate ◽  
Test Methods ◽  
Sulfate Attack ◽  
Ettringite Formation ◽  
Heating And Cooling ◽  
Friedel’S Salt ◽  
Lime Solution ◽  
Internal Sulfate Attack

Recently in Quebec Canada, concrete structures suffered very rapid deterioration within 3 to 5 years of construction. The deterioration was caused by an iron sulfide, namely pyrrhotite, in the coarse aggregate that suffered oxidation inside concrete and promoted sulfate attack; indicated by the presence of ferric oxyhydroxides (“rust”), gypsum, ettringite, and thaumasite. The goal of the current work was to reproduce this reaction under accelerated laboratory conditions, in progression of a performance test. Conditions to promote pyrrhotite oxidation and internal sulfate attack were provided; exposure cycles were tested with heating and cooling, and saturation in oxidizing agents or lime solution. Oxidation was induced in concrete samples, however, other mechanisms contributed to deterioration. The bleach was found to promote NaCl and Friedel’s salt formation, furthermore, it seemed to mitigate expansion from sulfate attack. Sulfoaluminate decomposition was also found to cause secondary ettringite formation. More optimization to the test methods was recommended.

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