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ABSTRACT
The internal sulfate reaction by the deferred formation of ettringite was discovered in steamed precast elements. It was identified only a few years ago as being responsible for disorders likely to damage cast-in-place structures where the concrete of which has reached high temperatures. This article starts by presenting the mechanisms of thios reaction and the various types of ettringite. On the basis of the description of the disorders, it then describes the pathology and management of sick structures and the prevention to be implemented. Fundamental and applied researches are still necessary in order to improve the current knowledge.
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Read the articleAUTHORS
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Bruno GODART: Technical Director, Civil Engineering Works, LCPC (Laboratoire Central des Ponts et Chaussées)
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Loïc DIVET: Head of the Physico-chemistry of Materials division at the Laboratoire Central des Ponts et Chaussées (LCPC)
INTRODUCTION
Internal sulfate reaction (ISR) through the delayed formation of ettringite is a cause of disorders that can severely damage concrete structures.
The first cases appeared abroad, from 1987 onwards, in certain prefabricated parts that had been subjected to heat treatment inappropriate to the formulation and exposure of the concrete (e.g. railroad sleepers).
Since 1997, this phenomenon has been observed in France on bridges where the concrete had been cast in place. These are mainly massive structures (piers, headers on piers or abutments, etc.) in contact with water or subject to high humidity.
Unlike more conventional sulfate reactions, where sulfates attack the concrete from the outside, causing progressive degradation from the surface to the core, RSI affects the entire concrete without the need for an external source of sulfates. The result is swelling of the material and cracking of the structure.
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Internal sulfate reaction in concrete structures
Mechanism of the internal sulfate reaction
Bibliography
References
Standards and norms
- Cement – Part 1: Composition, specifications and conformity criteria for common cements. - NF EN 197-1 -
- Amendement A1 à la norme NF EN 197-1. - NF EN 197-1/A1 -
- Concrete – Part 1: Specification, performance, production and conformity. - NF EN 206-1 -
- Amendement A1 à la norme NF EN 206-1. - NF EN 206-1/A1 -
- Amendement A2 à la norme NF EN 206-1. - NF EN 206-1/A2 -
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