Assessing Alkali-Silica Reaction Performance in Eco-Efficient Concrete: Influence of Alkali Boosting

The concrete prism test (CPT) is considered the most reliable standardized laboratory test procedure to evaluate alkali-silica reaction (ASR) worldwide; yet to overcome leaching related issues, alkalis are added to the concrete mixture in this procedure. Research on conventional concrete has shown that regardless of the aggregate’s reactivity, the higher the alkali loading, the greater the overall expansion of concrete, indicating that the alkali loading is a key parameter to assess conventional mixtures. However, further research is required to evaluate the effectiveness of applying the CPT to appraise eco-efficient mixtures developed with low cement/alkali content. Hence, this study compares ASR-induced expansion and damage development of two mixtures with distinct cement contents (420 and 250 kg/m³). The mixtures were tested under boosted and non-boosted conditions using the conventional CPT and an adopted encapsulated procedure. The results show that increasing the alkali loading has a greater influence on the overall expansion of mixtures with lower cement content. Moreover, analyzing the damage rating index (DRI) and distress features (without weighting factors) of mixtures with similar expansion, it was concluded that boosted mixtures had more open cracks indicating the impact of accelerating the expansion development caused by the alkali boosting. The results highlight the need for additional research to evaluate and develop ASR-test protocols in order to achieve comparable distress feature data between laboratory and field samples.