Effect of two activation methods on mechanical properties of high volume fly ash binders

Abstract

In this work, the effects of mechanical and chemical activation, as well as their combination, on the mechanical properties of high volume fly ash (HVFA) binders were investigated. Mechanical activation was conducted by grinding fly ash (FA) in a planetary ball mill. It resulted in drastic particle size reduction and increase in specific surface area of the FA. Morphology of FA particles, examined by scanning electron microscope, was also changed. The chemical activation was carried out by adding sodium sulfate to the dry mass of the binder. Effects of the activation methods on mechanical properties of the resulting binders were examined by determining setting time and compressive strength of HVFA mortars. The results showed that both activation methods lead to significant decrease in setting time and increase in early compressive strength, especially when combination of both of the activation methods was applied. Thus, properties of HVFA binders that have been limiting their use in the construction industry, i.e. long setting time and low early strength, were improved by using mechanical and chemical activation.