(Received 2 October 1998; accepted 9 July 1999)
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Several test methods are available to evaluate the potential susceptibility of concrete-making materials to deleterious alkali-silica reactions (ASR). These methods vary in the approaches they use to accelerate the reaction; acceleration being necessary to provide timely evaluations of materials in predicting long-term performance. As a consequence, the tests are not universally applicable, nor do they necessarily provide straightforward, consistent results using established criteria. This paper compares results of C 441 and C 1293 tests in an effort to develop specification criteria for ASR-resistant concrete.
ASTM C 441 uses Pyrex glass aggregate in mortars to accelerate the testing and provides reliable results in 2 months. It can be used to evaluate the effectiveness of pozzolans and ground slag to prevent expansions, as well as the effect of portland cements on the reaction. However, differences in the relative reactivity of Pyrex glass and the aggregates used in concrete construction should be considered in the engineering decision-making process. The C 1293 test has the advantage of testing the natural aggregates available for use in construction and achieves acceleration by artificially raising the alkali content of the concrete. Its disadvantages are that it takes at least 1 to 2 years for results, and cannot be used to evaluate the effectiveness of portland cements in resisting ASR.
C 1293 results can be considered to have more relevance to actual field constructions than results from C 441 tests because it tests construction aggregates. However, the 1 to 2 year testing period makes it impractical for general specification purposes. This paper illustrates the use of C 1293 results to determine which cementitious materials are effective in controlling the reactivity of a particular aggregate, coupled with C 441 testing of those same materials to establish an expansion limit in C 441 tests. The limit established for C 441 tests provides for timely testing that should be applicable to common hydraulic cementitious materials.
Senior research scientist, Virginia Transportation Research Council, Charlottesville, VA
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