Influence of Sintering Temperature of Kaolin, Slag, and Fly Ash Geopolymers on the Microstructure, Phase Analysis, and Electrical Conductivity

• Main Authors: Nur Nadiah Izzati Zulkifli, Mohd Mustafa Al Bakri Abdullah, Anna Przybył, Paweł Pietrusiewicz, Mohd Arif Anuar Mohd Salleh, Ikmal Hakem Aziz, Dariusz Kwiatkowski, Marcin Gacek, Marek Gucwa, Jitrin Chaiprapa
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: Materials
• Subjects: geopolymer; microstructure analysis; phase analysis; electrical conductivity; sintering temperature
• Online Access: https://www.mdpi.com/1996-1944/14/9/2213
• ISSN: 1996-1944

This paper clarified the microstructural element distribution and electrical conductivity changes of kaolin, fly ash, and slag geopolymer at 900 °C. The surface microstructure analysis showed the development in surface densification within the geopolymer when in contact with sintering temperature. It was found that the electrical conductivity was majorly influenced by the existence of the crystalline phase within the geopolymer sample. The highest electrical conductivity (8.3 × 10⁻⁴ Ωm⁻¹) was delivered by slag geopolymer due to the crystalline mineral of gehlenite (3Ca₂Al₂SiO₇). Using synchrotron radiation X-ray fluorescence, the high concentration Ca boundaries revealed the appearance of gehlenite crystallisation, which was believed to contribute to development of denser microstructure and electrical conductivity.