Investigating Aluminasilicate Source in Geopolymer Compressive Strength: Surface Morphology and Crystal Phase Study

Anggarini Ufafa1* and Sukmana Ndaru Candra2
1. Department of Chemical Engineering, Universitas Internasional Semen Indonesia, Jln.Veteran Kompleks PT Semen Indonesia,
Gresik-East Java, INDONESIA
2. Department of Engineering Management, Universitas Internasional Semen Indonesia, Jln.Veteran Kompleks PT Semen Indonesia,
Gresik-East Java, INDONESIA
*ufafa.anggarini@uisi.ac.id

Abstract

In this present study, geopolymer, which is a cementitious specimen was synthesized with Fly and Bottom Ash to form aluminosilicate source. The geopolymer was synthesized by sol gel method at SiO2/Al2O3 ratio of 4. The percentage of SiO2 weight in fly ash was higher than bottom ash which was about 31.96 wt% and 21.07 wt% for each material. The Al2O3 content in fly ash also has a higher value than bottom ash at 22,62 wt% and 5.92 wt%, respectively. In order to study the surface morphology and X-ray Diffraction (XRD) for crystal phase analysis, the characteristics of Geopolymer from fly ash and bottom ash were compared using the Scanning Electron Microscope (SEM).

The diffractogram result showed that geopolymer that synthesized from fly ash has a higher amorphous phase than bottom ash geopolymer, which indicated that fly ash geopolymer is not only more reactive than bottom ash geopolymer, it also has an impact on good polymerization processes. This result is parallel with the SEM result that shows fly ash geopolymer has less unreacted particle than bottom ash geopolymer. It was found that reactive SiO2 and Al2O3 in fly ash produced geopolymer with a high compressive strength of 68 Mpa while bottom ash produced geopolymer with the compressive strength of 51 Mpa

Keywords: Geopolymer, Fly ash, Bottom ash, SEM, XRD

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