ASTM C227
Full Name
ASTM C227 – Standard Test Method for Potential Alkali Reactivity of Cement-Aggregate Combinations (Mortar-Bar Method)
Scope
ASTM C227 focuses on determining the potential of cement-aggregate combinations to experience expansive reactions due to alkali-silica reaction (ASR). This reaction involves the alkalis (sodium and potassium) in cement reacting with certain siliceous minerals in aggregates, leading to the formation of expansive gels that can cause cracking and deterioration in concrete.
Specifically, the standard covers:
- Preparation of mortar bars: the standard outlines the procedure for preparing mortar bars with specific proportions of cement, aggregate, and water.
- Storage conditions: it specifies the controlled storage conditions for the mortar bars, including temperature and humidity, to promote ASR.
- Length change measurement: the test measures the length change of the mortar bars over time, typically 14 and 28 days. Excessive expansion indicates potential alkali reactivity.
- Interpretation of results: the standard provides criteria for interpreting the test results to assess the potential alkali reactivity of the cement-aggregate combination.
The mortar-bar method is a long-term test and is considered a reliable indicator of potential ASR in concrete. However, it does not provide a direct measure of the expansion that may occur in concrete structures.
ASTM C227 is essential for:
- Selecting suitable aggregates: evaluating the potential alkali reactivity of aggregates helps in selecting suitable aggregates for use in concrete, especially in environments with high alkali content or where ASR is a concern.
- Preventing ASR-related damage: identifying potentially reactive combinations allows for preventive measures, such as using low-alkali cement or supplementary cementitious materials, to mitigate the risk of ASR-induced damage in concrete structures.
- Quality control: the test can be used for quality control purposes to ensure that the aggregates used in concrete meet the specified requirements for alkali reactivity.
ASTM C227 Accredited Laboratory
Applied Testing & Geosciences, LLC is accredited for performing tests using the ASTM C227 standard.
Contact us today to learn more about our testing capabilities and how we can support your business.
Resources
Keywords
alkali-silica reaction; mortar bar; cement-aggregate combination; expansion; length change; alkalies; silica; reactive aggregate