Standard Test Method for Potential Alkali Reactivity of Aggregates (Mortar-Bar Method)
4.1 This test method provides a means of detecting the potential of an aggregate intended for use in concrete for undergoing alkali-silica reaction resulting in potentially deleterious internal expansion. It is based on the NBRI Accelerated Test Method (1-4).3 It is especially useful for aggregates that react slowly or produce expansion late in the reaction. However, it does not evaluate combinations of aggregates with cementitious materials nor are the test conditions representative of those encountered by concrete in service.
4.2 Because the specimens are exposed to a NaOH solution, the alkali content of the cement is not a significant factor in affecting expansions.
4.3 When excessive expansions (see Appendix X1) are observed, it is recommended that supplementary information be developed to confirm that the expansion is actually due to alkali-silica reaction. Sources of such supplementary information include: (1) petrographic examination of the aggregate (Guide C295/C295M) to determine if known reactive constituents are present; (2) examination of the specimens after tests (Practice C856) to identify the products of alkali reaction; and (3) where available, field service records can be used in the assessment of performance.
4.4 When it has been concluded from the results of tests performed using this test method and supplementary information that a given aggregate should be considered potentially deleteriously reactive, the use of mitigative measures such as low-alkali portland cement, mineral admixtures, or ground granulated blast-furnace slag should be evaluated (see last sentence of 4.1).
1.1 This test method permits detection, within 16 days, of the potential for deleterious alkali-silica reaction of aggregate in mortar bars.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. When this test method refers to combined-unit standards, the selection of the measurement systems is at the user’s discretion.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. A specific precautionary statement is given in the section on Reagents.
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