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Detection of ASR aggregates by dissolution experiments : a new approach
Publikationstyp
Conference Paper
Date Issued
2021
Sprache
English
Author(s)
Start Page
344
End Page
351
Citation
fib Symposium of Concrete Structures: New Trends for Eco-Efficiency and Performance (2021)
Contribution to Conference
Scopus ID
Peer Reviewed
true
The alkali-silica reaction (ASR) is a significant damage process of concrete. Amorphous or crypto-crystalline parts of the aggregate react with alkalis from the cement or from outside the structure to alkali-silica gel. The ASR causes damage by the expansion of the gel through the absorption of water. Since it was first detected in 1940, much research has been carried out on the conditions, the various stages and how to prevent the reaction. However, there are still parts that have not been clearly and fully understood. Different national tests have been developed to identify the respective locally occurring alkali-reactive aggregates. These test methods usually require days to months before delivering reliable test results. The concrete or mortar test specimens are generally cubes or prisms with a standardized recipe. So far there is no very fast and reliable testing method for the detection of alkali-reactive aggregates. The Institute of Materials, Physics and Chemistry of Buildings at Hamburg University of Technology is developing a new test method to identify alkali-reactive aggregates. This method is set to work without the effort of producing specially test specimens. An additional requirement is that this method should be able to serve as an incoming goods inspection. The alkali reactivity of the aggregate should be derived from the change of chemical and physical parameters and the reaction kinetics during accelerated dissolution experiments. Acceleration is achieved by a temperature of 60°C, a pH of 14 by 1M potassium hydroxide solution and a maximized surface area of the aggregate by grinding it into flour. The measured parameters are the pH-value, the electrical conductivity, and the redox potential. In this contribution the new test method is introduced, first results are presented and the possibility of using the pH-value as an indicator of the alkaline reactivity is discussed.
Subjects
Alkali silica reaction
test methodology
DDC Class
540: Chemie
600: Technik
620: Ingenieurwissenschaften
690: Hausbau, Bauhandwerk