Synthesis and Characterization of Geopolymers from Coal Gangue, Fly Ash and Red Mud
Geopolymers are inorganic aluminosilicate polymers which have been synthesized from pure sources and more recently, from industrial byproducts. In this study, the industrial by-products, coal gangue, fly ash and red mud were used to synthesize geopolymers at low and elevated temperatures. NaOH, which is often used to raise the pH of the mixture, has been partly replaced using red mud. The strength characteristics of geopolymers synthesized using binary mixtures of coal gangue and red mud as well as ternary mixtures of coal gangue, fly ash and red mud were examined. The compressive strength of the end products was determined using unconfined compression tests. The textural and morphological properties of the end products were also studied. The results reveal the influences of temperature and Si/Al and Na/Al ratios of the raw materials in the geopolymerization reactions and the subsequent development of strength, textural and morphological characteristics. The binary mixtures of coal gangue and red mud showed an increase in strength with curing temperature while the ternary mixtures of coal gangue, fly ash and red mud developed higher strength at lower curing temperatures.
KeywordsGeopolymer Synthesis Coal gangue Fly ash Red mud
The financial support from the National Natural Science Foundation of China (Project No. 41372352, 51579132), and Tsinghua University (Project No. 2015THZ02-2, 2015THZ01) are gratefully acknowledged. The support for the testing facility from State Key Laboratory of Hydro Science and Engineering (SKLHSE-2016-D-03) is also acknowledged.