Influence of Temperature and Storage Solution Composition on Test Methods for Alkali-silica Reactivity

The concrete prism test (CPT, ASTM C1293, CSA A23.2-14A) and the accelerated mortar bar test (AMBT, ASTM C1260, ASTM C1567, CSA A23.2-25A), commonly used for evaluation of alkali-silica reaction (ASR), have limitations. The main disadvantage with the AMBT is that some field innocuous aggregates are incorrectly identified as reactive (false-positives) and some field reactive aggregates are incorrectly identified as non-reactive (false-negatives). The shortcoming associated with the more accurate CPT is its lengthy testing period of 1 to 2 years. This study attempts to improve these methods by evaluating the influence of temperature and composition of storage solution. At 80C in 1N NaOH storage, AMBT samples have different pore solution compositions than cement pastes cured at ambient temperatures. Changes in pore solution composition were found to lead to changes in the type and composition of ASR products. For more accurately representing paste pore solutions and resulting ASR products, the storage solution and the temperature of the AMBT were modified to 0.65N KOH+0.150N NaOH at 60C. Contradictory to what was expected, the modification did not dramatically improve test accuracy. However, the modified test appeared to still be better alternative to the standard AMBT, especially for aggregates that show pessimum behavior. The concrete prism test modified to 60C storage was also assessed and was found to be more promising than the modified AMBT. This modified test was almost as accurate as the standard CPT and the test period was reduced to only 3 to 6 months.Ph.D