ISSN: 0149-6123
Page Count: 9

Measurement of the Alkali Content of Concrete Using Hot-Water Extraction
Bérubé, M-A
Professor, Université Laval, QC

Frenette, J
Research Assistant, Université Laval, QC

Rivest, M
Project Engineer, Direction Ingénierie, Hydro Québec, QC

Vézina, D
Concrete Engineer, Laboratoire des chaussées, Ministry of Transportation of Québec, QC

(Received 4 June 2001; accepted 5 April 2002)

Abstract

The knowledge of the active- or soluble-alkali content of concrete is useful in the diagnosis and prognosis of alkali-aggregate reactivity (AAR). A method often used for determining this content is hot-water extraction from ground concrete samples. This method was applied to 17 aggregates and 8 concretes incorporating aggregates presenting different degrees of alkali-silica or alkali-carbonate reactivity. The following conclusions can be drawn: (1) a correction must be made to take account for the alkalies released by the aggregates in the test; (2) using cold water rather than hot water has no significant effect on the results; (3) grinding to <160 μm appears more appropriate than <80 μm (lower amount of alkalies released by the aggregates); (4) the soluble-alkali content progressively decreases as alkali-silica reaction (ASR) progresses, which indicates that a significant part of alkalies, progressively incorporated in the reaction products from ASR, is not leached in the test; (5) the repeatability from one series of tests to another and the reproducibility from one laboratory to another appear relatively poor; (6) the use of a control concrete with a known soluble-alkali content may greatly improve the repeatability and the reproducibility of the method.

Keywords:
Aggregate, alkali, alkali-aggregate reaction, alkali-carbonate reaction, alkali-silica reaction, concrete, soluble alkalies, test method, water-extraction

Paper ID: CCA10489J
DOI: 10.1520/CCA10489J
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