Preparation of Briquette by Brown Coal Gangue-blast Furnace Slag Geopolymer Binder and Its Characteristics

Effective recycling of industrial waste is a very important issue worldwide. Coal gangue is a solid waste generated during coal production and processing, which accounts for 10-20% of coal production, the largest of industrial wastes discharged so far. Geopolymers are three-dimensional amorphous inorganic polymers in the form of Si-O-Al-O-Al, in which silica and alumina precursors with high reaction activity are formed via depolymerization-condensation processes in a highly alkaline environment. In this paper, a geopolymer binder is prepared by combining an alkaline activator prepared from brown coal gangue and blast furnace slag as raw material and from industrial waste silica fume. Also, the properties of these geopolymer binders are examined using them as a briquette binder. At temperatures above 700°C, roasted brown coal gangue is more active than the initial state. The optimum dosage of alkali activator is 10M NaOH, silica fume/NaOH ratio of 3, specific gravity of 1.42, and the addition of binder of 6%. The main polymerization products of the alkali activated brown coal gangue geopolymer samples are N-A-S-H gel and amorphous aluminosilicate gel, while the main polymerization products of the alkali activated brown coal gangue -blast furnace slag geopolymer samples are N-A-S-H gel, C-(A)-S-H gel and amorphous aluminosilicate gel. Blast furnace slag is added during the preparation of briquette binder by brown coal gangue geopolymer, which increase the mechanical strength of the geopolymer binder and the optimum dosage is 30%.