Assessing Alkali Silica Reaction in Low-Alkali Concrete Mixtures: A Comparative Study of Test Setups

As sustainability measures in the construction industry aim to reduce cement use, the reactive potential of low-alkali mixtures must be further evaluated. While the concrete prism test (CPT) is the most reliable laboratory procedure for determining aggregate’s reactivity, leaching that occurs during the test can compromise the accuracy of results. To overcome this limitation, alkalis are boosted in CPT specimens by adding NaOH to the mixing water, but further studies are required to understand if this approach is suitable for evaluating the reactivity of aggregates in low-alkali mixtures. This study compares three test setups (CPT, soaked, wrapped, and encapsulated) to evaluate ASR-induced expansion and damage development of boosted and non-boosted mixtures with low amounts of alkalis. The results show that regardless of the testing protocol, mixtures reach similar ultimate expansion when the total system alkali content is as low as to 3.61 kg/m3, yet the ASR-kinetics and crack features of CPT mixtures are accelerated and exacerbate due to alkali boosting when compared to non-boosted mixtures.