Assessment of the potential alkali-reactivity of slow-reacting aggregates from the province of Buenos Aires, Argentina

Determination of the potential reactivity of slow-reacting aggregates has been an openly debated subject worldwide for decades, and it remains ongoing. The province of Buenos Aires is the main producer of concrete aggregates in Argentina, and many quarries exploit migmatites and granites affected by deformation processes. Therefore, it is important to determine their potential behavior in concrete as they can cause alkali–silica reactions. The objective of this study is to determine the potential reactivity of aggregate samples from seven quarries of this sector by different methods and evaluate their performance. Petrographic studies were carried out according to the Instituto Argentino de Racionalización de Materiales (Argentine Normalization and Certification Institute; IRAM) 1649 standard, and different microstructural characteristics of quartz were quantified. The potential reactivity of the aggregates was evaluated by three expansion test methods, namely, the accelerated mortar-bar test (AMBT), the concrete prism test at 38 °C (CPT), and the accelerated concrete prism test at 60 °C (ACPT). The content of microcrystalline quartz (grain size < 60 μm) was found to correlate very well with the expansion measured in the AMBT and CPT when the limits and testing time of the IRAM standards were adopted. However, no correlation was found with the ACPT, and the results of this test were contradictory to those of the AMBT and CPT. Based on these results, a limit of 5 vol% of microcrystalline quartz appears to be adequate to differentiate reactive from non-reactive behaviors in the rocks studied.