In this study, the Palm Oil Fuel Ash (POFA) was used as a raw material for making geopolymer mortars that uses a combination of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). The purpose of this study was to determine the effect of various parameters on the compressive strength of mortars. The parameters involved were namely modulus of activator ratio (Ms 1-3), the molarity of NaOH (10-16M), curing temperature (28-110ºC), type of POFA particle processing (oven-dried, passed the #200 sieve, burned in a brick kiln, burned at 800ºC), rest periods of 3 and 5 days. Based on the parametric study, it was found the optimum mixture with the highest compressive strength consisted of NaOH 14M, Ms ratio of 2.5, curing temperature of 100OC, a rest period of 5 days, particles sieved using #200 sieve and had 15% PCC content.

Fly ash is industrial residue from the coal combustion in electric and steam generating plants and recognized as an environmental pollutant. Fly ash contains a high concentration of silica and alumina and can be used as geopolymer concrete. Studies the use of fly ash as a geopolymer concrete mixture has been developing in recent decades. This review focuses on the characteristics of fly ash as hybrid geopolymer concrete, and its resistance is peat environment. The hybrid geopolymer is made by activating fly ash using an alkaline activator and Portland cement. The addition of fly ash geopolymer concrete with Portland cement forms N-A-S-H bond structure from fly ash, and C-S-H hydration bond from Portland cement forms C-A-S-H, which is more solid and stronger against aggressive environment such as peat. In addition, the geopolymer concrete is proven to be able to mobilize heavy metals in fly ash so the concrete has low leaching rate and not harmful to the peat ecosystem. This review proves that hybrid geopolymer concrete using fly ash is a potentially innovative and promising material in the future. The geopolymer hybrid not only has its resistance to peat and acts as conservative material in an environmentally friendly peat environment.