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Alkali Reactivity Testing

Alkali Reactive Test Method ASTM C289: Cement Testing

ALKALI REACTIVE TESTING, also known as alkali silica reaction (ASR) testing, is a critical procedure used to assess the potential reactivity of aggregates in concrete structures and chemical compositions. The alkali silica reaction refers to a chemical reaction between the alkaline solutions in concrete and reactive silica present in certain aggregates, resulting in deleterious internal expansion. The concern? Potentially deleterious internal expansion.

To conduct this test method, hardened concrete prisms or mortar bars are prepared with the reactive aggregate combinations to be tested. These specimens are then subjected to a highly alkaline solution, typically a sodium hydroxide (NaOH) solution, which simulates the concrete pore solution. Over a specified test duration, the expansion due to alkali of the specimens is monitored and measured in concrete structure.

The test results obtained from alkali reactive testing with ion concentration provide valuable information about the potential for concrete deterioration caused by ASR. Petrographic examination of the specimens can also be conducted to evaluate the mineralogical composition and assess the presence of reactive grains in known field performance.

Several test methods, such as the mortar bar method and the concrete prism test, have been developed to assess alkali reactive tests. These methods involve measuring length changes or expansion of the specimens due to alkali silica reactivity and silica reactivity of aggregates.

Alkali reactivity testing is crucial for assessing the suitability of aggregates for use in concrete mixes, as it helps prevent potential damage to concrete over time. By determining the potential reactivity of aggregates, engineers can make informed decisions in selecting appropriate materials and controlling the alkali content in cementitious mixtures. This ensures the long-term durability and performance of concrete in various field conditions. An indispensable part of aggregate testing.

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