Method for manufacturing coal-based geopolymer foam including silica fume

A method for manufacturing geopolymer foam with coal ash, the method comprising the steps of:

• (1) mixing water glass (Na2SiO3) and sodium hydroxide (NaOH) to prepare an alkali activator;
• (2) adding silica fume as blowing agent to the alkali activator and stirring the same;
• (3) pulverizing coal bottom ash;
• (4) mixing the coal bottom ash with coal fly ash to prepare coal ash;
• (5) adding the mixture of silica fume and the alkali activator to the coal ash and then further adding the alkali activator to adjust a ratio of alkali activator/solid material comprising the coal ash and the silica fume, followed by mixing the same;
• (6) loading and sealing the mixture in a mold to prepare a specimen;
• (7) curing the specimen in an oven;
• and
• (8) exposing to a temperature of as high as 200° C. to 600° C. for 2 hours the specimen that has completely undergone the curing,
• wherein the coal fly ash is contained in an amount of 10 to 50% by weight based on the total weight of the coal bottom ash and the coal fly ash in step (4),
• wherein the ratio of alkali activator/the solid material comprising the coal ash and the silica fume ranges from 0.38 to 0.50 in step (5).