Effect of relative humidity on the reaction products of alkali activated fly ash

The alkali activation of fly ash (AAFA) is a chemical process in which the ash is mixed with an alkaline activator and cured at a mild temperature to generate compact solids. Both the curing conditions (temperature, time, relative humidity, etc.) and the nature and concentration of the alkali activator play a key role in the development of AAFA micro- and nanostructure, and consequently the properties of these materials. In the present study, fly ash was activated with a 15% water-glass (Na2SiO3) + 85% 10-M NaOH solution at 85 °C for 12 h, 7 and 30 days. Two curing methods were used, in which the variable was the relative humidity (RH).