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Numerous instances have been recorded where the use of low alkali cement with certain volcanic aggregates has failed to prevent deleterious alkali-silica reactivity. Present testing using the ASTM Test for Potential Alkali Reactivity of Cement-Aggregate Combinations (Mortar-Bar Method) (C 227) may fail to identify this reactivity because testing is normally done with only high alkali cements. It is recommended that concurrent testing be done, using a range of both high and low alkali cements, to determine that maximum safe cement alkali level for each aggregate in question. Although the traditional limit of 0.60% alkali has prevented alkali aggregate reaction with many reactive aggregates, there are certain volcanic aggregates that require even lower alkali or the use of suitable pozzolanic materials to avoid alkali aggregate reactivity or both.
Principal research petrographer, Portland Cement Association, Skokie, Ill.
Stock #: CCA10189J