Alkali-silica reaction (ASR) is a concrete degradation phenomenon in which the alkalis that are typically found in concrete react with certain amorphous or micro-crystalline siliceous phases in the aggregate and, in the presence of moisture, form an expansive gel that is capable of cracking the concrete and generating macroscopic expansion. As the cracking occurs and progresses, there is a loss of the mechanical properties of the concrete, and a commensurate decrease in the structural capacity of the affected elements. Unfortunately, there is no standard guide or industry best practice for quantifying the changes in the mechanical properties and the commensurate changes in the capacity. Furthermore, ASR is a complex chemical phenomenon, the rate and extent of which depend upon a number of material and environmental parameters. Therefore, although there are standardized tests to characterize the susceptibility of a concrete mixture design to future ASR degradation, there is no standardized procedure for assuring that a concrete mixture will be sufficiently immune to ASR so that it will continue to function throughout its intended service life. A scoping study of alkali-silica reaction in concrete is used to summarize the current state of knowledge with respect to the effect that ASR has on the degradation of mechanical properties. This includes evaluating both the current and the future capacity of a structure. The summary is divided among specific technical barriers that contribute to evaluating capacity. The summary is then used to identify knowledge gaps for each technical barrier. A technical plan is developed for meeting the knowledge gaps and for providing the tools for service life prediction of ASR affected concrete structures.
Citation: NIST Interagency/Internal Report (NISTIR) - 7937
NIST Pub Series: NIST Interagency/Internal Report (NISTIR)
Pub Type: NIST Pubs
cement, fly ash, microscopy, salt waste, saltstone, service life, slag