The Effect of Various Fly Ash Content on Geopolymer Concrete with Different Curing Regime

Environmental problems associated with cement production had long been recognized
and concerns of reducing the impact from cement industry had arisen globally.
Therefore, the urge to replace usage of cement in concrete with other materials h? s
become the main focus in construction industry nowadays. Fly ash as a waste material
resulted from combustion of coal in the electrical power plant, had also contributed to
environmental problems due to abundance of fly ash that was disposed to the landfills.
However, fly ash is a pozzolanic material that contain high amount of aluminium and
silicon which has high potential to replace cement. In this research, Geopolymer
Concrete had been developed by incorporating fly ash as the main binder and completely
eliminated the used of cement. Various fly ash densities was used in this research which
are 250,300,350,400 and 450 kg/m3, in order to identify the optimum proportion of fly
ash in Geopolymer Concrete. The Geopolymer Concrete was cured under 3 different
curing regimes which are ambient, external exposure and oven curing, to identify the
effect of curing regime on concrete strength. The compressive strength were tested on 3,
7,28 and 56 days for ambient and external exposure curing, while 1,3,7, and 28 days
for oven curing. Besides, the inner properties of Geopolymer Concrete was also studied.
The other materials used to develop this concrete are 8M sodium hydroxide, sodium
silicate, aggregates and extra water. In the manufacturing process, all the solid
components were dry mixed for 2.5 minutes and continued with wet mixed for another
1.5 minutes by added all the liquid components. Th-. Geopolymer Concrete was
manufactured by adopting the same equipment as OPC Concrete. It is concluded that the
optimum mix proportion of' fly ash in Geopolymer Concrete were recorded as 300,350
and 400 kg/m3 for ambient, external exposure and oven curing respectively. The results
showed that curing regime had significant impact on concrete compressive strength.
Oven curing concrete had the highest compressive strength compared to other concretes.
The inner properties of Geopolymer Concrete was studied by conducting Field Emission
Scanning Electron Microscopy (FESEM) Analysis. From the images of concrete
obtained, the relation between the Interfacial Transition Zone (ITZ) with compressive
strength was verified.