Alkali-silica reactivity criteria for concrete aggregates

In this study, the suitability of the threshold alkali level, TAL, the kinetic parameter, In k, and the microstructural disorder coefficient, Cd, of the aggregates, taken as alkali-silica reactivity criteria, was assessed using different typologies of Italian natural ASR-susceptible aggregates of known field performance. The TAL, In k, and Cd were determined using a modified version of the RILEM AAR-3 concrete prism expansion test, the ASTM C1260 mortar-bar expansion test, and the infrared spectroscopy test, respectively. It was found that the three reactivity criteria are all appropriate for discriminating between reactive and innocuous aggregates. However, the TAL proves to be a more suitable criterion for interpreting the field performance data of the aggregates investigated. There exists a linear relationship between TAL and In k, or between TAL and Cd, which provides a rapid means of estimating the threshold alkali levels of ASR-susceptible aggregates from the results of the ultra-accelerated mortar-bar test and/or the infrared spectroscopy test. A TAL-based classification of the degree of reactivity of the aggregates, as well as some modifications of the reactivity domains established by the infrared spectroscopy method are also proposed.