Geopolymer Synthesis Using Metakaolin and High Calcium Fly Ash as Binary System Geopolymer

Abstract

Conventional cement production process emits tons of carbon dioxide gas which is one of the greenhouse gases that influence the environment across the world. Discovering the alternative construction material with the eco-friendly process and the performance similar to or greater than ordinary Portland cement has been attractive to find out. This research presented green construction materials or so-called geopolymers from metakaolin substituted by high calcium fly ash by 20, 40, 60, 80 and 100 wt%. Some researches reported that geopolymer produced from metakaolin and fly ash with alkali solution gave a great result, but usually, they used fly ash containing very low calcium component. Compressive strength at 3, 7 and 28 curing days and flowability were conducted. The compressive strength of geopolymers blended with high calcium fly ash was still developed as the curing day increased and revealed the highest at 28 days especially on MK40 (high calcium fly ash 60 wt%). Geopolymer pastes prepared with a higher amount of high calcium fly ash exhibited less viscous. It was proved that the high amount of high calcium fly ash could be applied and gave extraordinary compressive strength. Furthermore, X-ray diffraction and X-ray fluorescence were used to investigate chemical properties as well as microstructure by a scanning electron microscope. For phase analysis, the existence of oxides of calcium and sulfur in high calcium fly ash resulted in the formation of thenardite, calcite, portlandite and C-S-H phase associating with geopolymeric phase. Therefore, this research proposed the opportunity for geopolymer production by using abundant high calcium fly ash to raise the value of the industrial waste products and green alternative construction material compared with OPC.