Standard Test Method for Length Change of Concrete Due to Alkali-Carbonate Rock Reaction

Importancia y uso:

4.1 Two types of alkali reactivity of aggregates have been described in the literature: the alkali-silica reaction involving certain siliceous rocks, minerals, and artificial glasses (1),3 and the alkali-carbonate reaction involving dolomite in certain calcitic dolomites and dolomitic limestones (2). This test method is not recommended as a means to detect combinations susceptible to expansion due to alkali-silica reaction since it was not evaluated for this use in the work reported by Buck (2). This test method is not applicable to aggregates that do not contain or consist of carbonate rock (see Descriptive Nomenclature C294).

4.2 This test method contains two methods. Method A is used to evaluate the susceptibility of a coarse aggregate to alkali-carbonate reaction. Method B is to evaluate the behavior of specific combinations of concrete-making materials to be used in concrete construction. However, provisions are made for the use of substitute materials when required. This test method assesses the potential for expansion of concrete caused by alkali-carbonate rock reaction from tests performed under prescribed laboratory curing conditions that will probably differ from field conditions. Thus, actual field performance will not be duplicated due to differences in wetting and drying, temperature, other factors, or combinations of these.

4.3 Use of this test method is of particular value when samples of aggregate from a source have been determined to contain constituents that are regarded as capable of participation in a potentially deleterious alkali-carbonate rock reaction either by petrographic examination, Guide C295/C295M, by the rock cylinder test, Test Method C586, by service record; or by a combination of these.

4.4 Results of tests conducted as described herein should form a part of the basis for a decision as to whether or not the aggregate under test can be used in portland cement concrete construction. Interpretation of results can be found in Guide C1778.

4.5 At the conclusion of the test it may be useful to conduct petrographic examination on the concrete following Practice C856/C856M and the aggregate following Guide C295/C295M to confirm that the aggregate causing expansive behaviour of the concrete, if any, is comparable to the petrography and chemistry of known deleteriously expansive alkali-carbonate reactive rocks. It is important to check the presence of potentially reactive silica that may not necessarily be visible at the scale of conventional transmitted light optical microscopy examination.

4.6 The research, evaluation, and precision and bias statement for this test method were done on crushed quarried carbonate coarse aggregate (3). Therefore, the results of evaluating alkali-carbonate reactive expansion of manufactured fine aggregate or natural sand containing crusher screenings derived from quarried carbonate rocks is unknown. Further, the applicability of this test to gravels containing carbonate rocks suspected of being alkali-carbonate reactive is unknown and as far as is known has not been evaluated.

Subcomité:

C09.50

Referida por:

C0586-19, C1778-23

Volúmen:

04.02

Número ICS:

91.100.30 (Concrete and concrete products)