Comprehensive semi-empirical approach to describe alkali aggregate reaction (AAR) induced expansion in the laboratory

Abstract

Describing alkali-aggregate reaction (AAR) induced expansion is a very complicated task, yet very useful to forecast and understand the potential of further deterioration of affected concrete. Back in the 90s, Larive developed an empirical model to describe AAR-kinetics in the laboratory. Although relatively well accepted by AAR community, Larive's equation is based on empirical mathematical parameters that do not have a clear physicochemical meaning and thus cannot directly describe AAR-induced development for a variety of materials and exposure conditions. This work proposes a novel semi-empirical model based on Larive's works and using five measurable parameters that directly affect AAR-induced development such as aggregate's type and nature/reactivity, alkali content of the concrete, temperature and external relative humidity. A comprehensive laboratory test campaign along with literature data are used to calibrate the proposed model. Coefficients from each of the above parameters are then established according to their influence on the chemical reaction. Results show that the proposed model may accurately describe AAR-induced expansion in the laboratory for a wide range of materials and exposure conditions without further calibration. Moreover, it can help identifying time periods and associate expansion levels for distinct accelerated test procedures.