Calcium enhanced ambient cured fly Ash based geopolymer binders

Abstract

This paper outlines the findings of an investigation on alkali activated fly ash mixtures to provide a comprehensive view of the effects of reactive oxide ratios on flowability, setting, compressive strength, early kinetics, and reaction products. Alkali-activated fly ash mixtures prepared based on reactive potential provide consistent strength under room-temperature conditions using low molarity sodium hydroxide. Under room-temperature curing, the low calcium dosage provided by 5% substitution of fly ash by slag leads to higher strength. The inclusion of slag enhances the early reactivity contributing to setting control. The early reactivity is enhanced with slag inclusion at a small proportion in the binder and the higher early kinetic activity contributes to larger fly ash dissolution. There is a synergistic enhancement of strength due to the enhanced formation of sodium alumino-silicate hydrate (NASH) geopolymers with the inclusion of slag. A systematic procedure for producing high compressive strength fly ash binders from the activation process of a given fly ash at room temperature curing is presented.