Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Alkali-silica reaction - A method to quantify the reaction degree
We propose a new chemical method for quantitative measurement of the reaction degrees of the alkali-silica reaction (ASR). We apply this method to a crushed natural reactive aggregate kept in contact with an alkaline solution, lime saturated by an appropriate amount of portlandite. This chemical system is designed to model the concrete capillary pores alkaline solution, in contact with reactive aggregates. Two reaction steps are taken into account in the mechanism: formation of Q3 sites made by breaking up siloxane bonds of the reactive silica and dissolution of these Q3 sites. The dissolution degree is measured by a selective acid treatment, and the nature of silica into solution is characterised by liquid NMR spectroscopy. The remaining silica is composed of Q4 tetrahedrons and Q3 protonated sites identified by solid NMR spectroscopy. These Q3 protonated sites are measured by thermogravimetry analysis. We show that the formation Q3 sites prevails on dissolution as the reaction progresses and contributes to an internal silica gel generation. The limiting step is the siloxane breaking up. Petrographic observations show that the reaction front penetrates in the aggregate through its porosity.
Alkali-silica reaction - A method to quantify the reaction degree
We propose a new chemical method for quantitative measurement of the reaction degrees of the alkali-silica reaction (ASR). We apply this method to a crushed natural reactive aggregate kept in contact with an alkaline solution, lime saturated by an appropriate amount of portlandite. This chemical system is designed to model the concrete capillary pores alkaline solution, in contact with reactive aggregates. Two reaction steps are taken into account in the mechanism: formation of Q3 sites made by breaking up siloxane bonds of the reactive silica and dissolution of these Q3 sites. The dissolution degree is measured by a selective acid treatment, and the nature of silica into solution is characterised by liquid NMR spectroscopy. The remaining silica is composed of Q4 tetrahedrons and Q3 protonated sites identified by solid NMR spectroscopy. These Q3 protonated sites are measured by thermogravimetry analysis. We show that the formation Q3 sites prevails on dissolution as the reaction progresses and contributes to an internal silica gel generation. The limiting step is the siloxane breaking up. Petrographic observations show that the reaction front penetrates in the aggregate through its porosity.
Alkali-silica reaction - A method to quantify the reaction degree
Bulteel, D. (Autor:in) / Garcia-Diaz, E. (Autor:in) / Vernet, C. (Autor:in) / Zanni, H. (Autor:in)
Cement and Concrete Research ; 32 ; 1199-1206
2002
8 Seiten, 24 Quellen
Aufsatz (Zeitschrift)
Englisch
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