(121f) Granulation of Wood Fly Ash Using a Geopolymer Binder

The amount of energy produced keeps rising, along with the waste, like fly ash, that comes
with it. At the same time, the demand for cement keeps growing, even though it already
accounts for 5-7% of the world CO2 production. Geopolymers made from alkali activated fly
ash offer a promising solution for this problem and research is already being done on this
topic. Unfortunately, a concrete-like mixture based on geopolymers requires alkali solutions,
which cannot easily be transported to the building sites. Instead, making geopolymer
granules out of alkali activated fly ash can be done separately, and these granules can
potentially replace gravel in cement.
In this research, the focus was on making granules out of wood fly ash, since some countries
use wood as their main source of electricity and therefore are left with wood fly ash, a waste
product that currently only has purpose as landfill. The main goal of this research was to
produce granules made out of a mixture of wood fly ash, ground granulated blast furnace
slag and a binder liquid and compare the strength of these granules to those based on coal
fly ash.
Producing the granules proved difficult, because coal fly ash and wood fly ash do not act the
same way in the granulator and initial batches gave very small granules.  
After creating both coal ash and wood ash based granules successfully, their strength could
be compared. It turns out that mixtures of coal ash and wood ash produce stronger granules
than just coal ash or wood ash, although the differences are small and for industrial
purposes, a material choice can be made based on availability.