Comparison of Results from C 441 and C 1293 with Implications for Establishing Criteria for ASR-Resistant Concrete

摘要

Several test methods are available to evaluate thepotential susceptibility of concrete-making materials to deleteriousalkali-silica reactions (ASR). These methods vary in theapproaches they use to accelerate the reaction; acceleration beingnecessary to provide timely evaluations of materials in predictinglong-term performance. As a consequence, the tests are notuniversally applicable, nor do they necessarily providestraightforward, consistent, results using established criteria. Thispaper compares results of C 441 and C 1293 tests in an effort todevelop specification criteria for ASR-resistant concrete.ASTM C 441 uses Pyrex glass aggregate in mortars to acceleratethe testing and provides reliable results in 2 months. It can be usedto evaluate the effectiveness of pozzolans and ground slag toprevent expansions, as well as the effect of portland cements on thereaction. However, differences in the relative reactivity of Pyrexglass and the aggregates used in concrete construction should beconsidered in the engineering decision-making process. The C1293 test has the advantage of testing the natural aggregatesavailable for use in construction and achieves acceleration byartificially raising the alkali content of the concrete. Itsdisadvantages are that is takes at least 1 to 2 years for results, andcannot be used to evaluate the effectiveness of portland cements inresisting ASR. C 1293 results can be considered to have more relevance toactual field constructions than results from C 441 tests because ittests construction aggregates. However, the 1 to 2 year testingperiod makes it impractical for general specification purposes.This paper illustrates the use of C 1293 results to determine whichcementitious materials are effective in controlling the reactivity ofa particular aggregate, coupled with C 441 testing of those samematerials to establish an expansion limit in C 441 tests. The limitestablished for C 441 tests provides for timely testing that shouldbe applicable to common hydraulic cementitious materials.