The increase in the POFA/FA percentage ratios result in increases
in the SiO2/Al2O3 ratios. High SiO2/Al2O3 cause the reaction
of aluminate species in the early stages and there is a scarcity of Al
species for further reactions at later stages. Hence it can be concluded
that geopolymerization is dominated by the reaction and
condensation of silicate species leading to gradual strength gains
at later stages. In addition, continuous development of the compressive
strength of POFA based geopolymer mortar between 28
and 112 days is about 38%, which contrasts with the FA based mortars
which gained 97% of their ultimate compressive strength by
day 7. The increase of POFA content which resulted in high SiO2/
Al2O3 up to about 34 and the elastic behaviour of compression failure
was observed to be elastic in the POFA based cube specimens
compared to brittle failure of FA based geopolymer specimens.
However, due to high silica content of POFA, it is worth investigating
the properties of POFA based geopolymer as a high temperature
resistant material. Hence, an independent study has been
conducted to address POFA based geopolymer properties at elevated
temperatures.