Mechanical and physical properties of fly ash geopolymer-mullite composites

This work aims to investigate how compressive strength of a typical class C fly ash-based geopolymer would be changed with addition of mullite. In preparation of basic geopolymer, fly ash was collected from Mae Moh power plants, Lampang province, was alkaline activated and cured for a total period of 7 days. In making the composites, 20-60% of mullite powder was added to the basic geopolymer mixture and cured at the same condition. Porosity, density, and water absorption of the samples were determined by following ASTM C-642. The results showed that the compressive strength of the geopolymer mortar could be remarkably improved from 14 MPa to 71 MPa with mullite addition. The mechanical property variation of the composites was discussed along with their physical properties and microstructures.