Method of quickly preparing geopolymer having high strength using coal bottom ash

A method of preparing a geopolymer using a coal bottom ash, the method comprising:

• a step (1) of preparing a mixture of the coal bottom ash and an alkali activating agent by performing mixing while an amount of the alkali activating agent is adjusted so that the mixture does not become a gel, wherein the mixture does not contain a gel;
• a step (2) of filling a mold with the mixture of the coal bottom ash and the alkali activating agent and applying a pressure thereto to thus prepare a geopolymer specimen;
• after the step (2), a step (3) of demolding the geopolymer specimen from the mold, and then curing only the geopolymer specimen in an oven for a predetermined period of time after the geopolymer specimen is demolded from the mold;
• and
• a step (4) of radiating a microwave on the geopolymer specimen after the curing, wherein an output or a radiation time of the microwave is adjusted to thus control a compressive strength and a thermal conductivity of the geopolymer in the step (4),
• wherein a content of the alkali activating agent is 0.40 based on 1 part by weight of the coal bottom ash in the step (1).