Rapid test method for determining alkali-silica reactivity expansion in concrete and aggregate.

摘要

The undesirable expansion of concrete due to a reaction between alkalis in the cement and reactive siliceous aggregates, known as alkali-silica reactivity (ASR), continues to be a world-wide problem. Current test methods for predicting ASR are either inaccurate because they are unrepresentative of field conditions or require long testing periods that become impractical for use in the field. Because of the rising interest to minimize distress caused by ASR, alternative methods must be considered.;A key factor in the prediction of ASR in concrete over time is the reactivity of the aggregate. In the present study, an attempt was made to develop a method for determining volumetric expansion of aggregate as a result of ASR. Since ASR is a thermally activated process, expansion rates at different temperatures can be used to determine the material's activation energy. This new method can categorize aggregates based on their reactivity over a short period of time and provides a unique parameter to evaluate ASR.;Results have indicated that the new method is effective in rapidly determining the volumetric expansion and activation energy in siliceous aggregates in sodium hydroxide. However, thus far the method is incapable of producing accurate results for non-siliceous aggregates, mortar, and concrete. In order to get accurate results for these materials a modified version of the testing method must be developed.