Determining aggregate reactivity in various alkaline solutions

Alkali–silica reaction was and still is a major issue of worldwide interest as it continues to have a detrimental effect on the long-term performance of concrete. Many researchers who focused over the years on the kinetics of alkali-silica reaction have found that the activation energy concept of alkali-silica reaction can serve as a material property to represent this kinetic-type combined effect of temperature, alkalinity, and time to evaluate alkali-silica reaction susceptibility of aggregate. However, a relationship determining the activation energy of alkali-silica reaction in various alkaline solutions is still lacking. To achieve this objective, a detailed study was conducted on different types of aggregates of different reactivity in order to formulate an aggregate test protocol that takes into account the main factors affecting alkali-silica reaction, such as alkalinity, temperature, and calcium concentration. Mathematical models have been proposed to determine alkali-silica reaction aggregate characteristics. Results indicate that the relationship between the activation energy and alkalinity appears to follow a power curve and that increasing the alkalinity of the solution beyond a certain level will only induce minimal change on the activation energy values. The chemistry of the alkali solution validates the laboratory research findings.