J. Korean Ceram. Soc. > Volume 52(4); 2015 > Article
 Journal of the Korean Ceramic Society 2015;52(4): 253. doi: https://doi.org/10.4191/kcers.2015.52.4.253
 Synthesizing and Assessing Fire-Resistant Geopolymer from Rejected Fly Ash Eung-Mo An, Young-Hoon Cho, Chul-Min Chon1, Dong-Gyu Lee2, Sujeong Lee Mineral Resources Research Division, Korea Institute of Geoscience and Mineral Resources1Geologic Environment Division, Korea Institute of Geoscience and Mineral Resources2Chungcheong Univ. Research Institute for Engineering & Technology ABSTRACT Ordinary Portland cement is a widely favored construction material because of its good strength and durability and its reasonable price; however, spalling behaviour during fire exposure can be a serious risk that can lead to strength degradation or collapse of a building. Geopolymers, which can be synthesized by mixing aluminosilicate source materials such as metakaolin and fly ash, and alkali activators, are resistant to fire. Because the chemical composition of geopolymers controls the properties of the geopolyers, geopolymers with various Si:Al ratios were synthesized and evaluated as fire resistant construction materials. Rejected fly ash generated from a power plant was quantitatively analyzed and mixed with alkali activators to produce geopolymers having Si:Al ratios of 1.5, 2.0, and 3.5. Compressive strength of the geopolymers was measured at 28 days before and after heating at $900^{circ}C$. Geopolymers having an Si:Al ratio of 1.5 presented the best fire resistance, with a 44% increase of strength from 29 MPa to 41 MPa after heating. This material also showed the least expansion-shrinkage characteristics. Geopolymer mortar developed no spalling and presented more than a 2 h fire resistance rating at $1,050^{circ}C$ during the fire testing, with a cold side temperature of $74^{circ}C$. Geopolymers have high potential as a fire resistant construction material in terms of their increased strength after exposure to fire. Key words: Geopolymer, Rejected fly ash, Compositional ratio, Compressive strength, Fire resistance rating
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