Alkali Reactivity Reaction Container
Supports the following standards: ASTM C289
For determining potential alkali reactivity of aggregates (chemical method) when used with high alkali cements. Stainless steel unit is 2" dia. x 2.25" high (51mm dia. x 57mm) fitted with air-tight cover. 50-75ML capacity.
Alkali reactivity, also known as alkali-aggregate reaction (AAR) or concrete expansion, is an important phenomenon studied in cement testing. It refers to the chemical reaction that occurs between the alkalis present in cement and certain reactive minerals in aggregates used in concrete. This reaction can lead to significant expansion and cracking of concrete structures, compromising their durability and integrity over time.
The main types of alkali reactivity are alkali-silica reaction (ASR) and alkali-carbonate reaction (ACR). ASR is the more common and well-studied form, involving the reaction between the alkalis in cement and certain types of silica minerals in aggregates, such as reactive forms of silica, opal, chalcedony, and volcanic glass. ACR, on the other hand, occurs when alkalis in cement react with certain types of carbonate minerals, like dolomite or limestone, present in aggregates.
To assess the alkali reactivity potential of cement, various testing methods are employed. These include the mortar bar test, concrete prism test, and petrographic examination of aggregates. In the mortar bar test, cement-aggregate mixtures are prepared and exposed to specific curing conditions. The expansion of mortar bars is measured over time to evaluate the reactivity of the materials. Concrete prism tests involve casting concrete specimens with potentially reactive aggregates, monitoring their expansion, and assessing their performance under different environmental conditions.
The significance of alkali reactivity testing lies in its role in selecting appropriate cement-aggregate combinations and designing durable concrete mixtures. By identifying reactive aggregates and adjusting the alkali content in cement, engineers can mitigate the risk of alkali reactivity, ensuring the long-term performance of concrete structures.
In conclusion, alkali reactivity testing plays a crucial role in evaluating the potential for expansion and cracking in concrete due to alkali-aggregate reactions. It helps engineers make informed decisions regarding material selection and mix design to ensure the durability and longevity of concrete structures.