The properties of palm oil fuel ash-fly ash based geopolymer mortar

The high silica content in fly ash (FA) and palm oil fuel ash (POFA) can be utilized as the main material of cement substitution. In this study, the geopolymer mortar made by mixing alkali activator Na2SiO3 and NaOH as activator and fly ash and palm oil fuel ash as precursor. Variations in the ratio of FA and POFA with the value of 75:25, 50:50 and 25:75. As well as the ratio of the alkaline solution between sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) of 1.5, 2.0, and 2.5. The objective of this study is to know the effects of NaOH and Na2SiO3 ratio to compressive strength on geopolymer mortar. The result of compressive strength test showed that the maximum compressive strength of mortar of 28 days was obtained by 22.08 MPa using alkali activator ratio of 2.5 with FA75:POFA25 and the minimum compressive strength obtained from comparison of FA25:POFA75 with alkali activator ratio of 1.5 was 3.7 MPa. It was showed that the use of FA75:POFA25 precursor and the greater alkali activator ratio used, the higher the compressive strength obtained. Further research will be developed to explore the potential of oil palm fuel ash based geopolymer concrete.