Advances in Test Methods to Evaluate Alkali-Aggregate Reactivity in Job Concrete Mixtures-The Role of Alkalis in Alkali-Silica Reaction Tests (Recorded presentation)

The Role of Alkalis in Alkali-Silica Reaction Tests (Recorded presentation)

Video Transcription

Video Summary

The presentation focused on understanding the role of alkalis in alkali-silica reaction (ASR) tests, emphasizing the importance of maintaining alkali balance in performance tests for concrete mixtures. Alkalis, primarily from Portland cement and supplementary materials, initiate and sustain ASR. The extent of ASR depends on available alkalis. While low alkali cement was once believed to prevent ASR, it is the total alkali burden that truly matters. Tests on real structures and exposure sites show ASR occurring even with low alkalis, suggesting the need for better job mixture tests. The speaker discusses how fly ashes often reduce ASR due to their ability to consume alkalis. This consumption can be more significant than merely diluting alkalis. Additionally, the presentation suggests revisiting standard testing methods and highlights the need for a method to evaluate alkali availability from aggregates, as these significantly impact ASR risk.

Keywords

alkali-silica reaction

alkali balance

concrete mixtures

fly ash

testing methods

alkali availability