Because fly ash has pozzolanic activity, it has been used for a long time as an admixture for concrete. However, unburnt carbon in the fly ash adversely affects the fresh properties of concrete. For this reason, when fly ash having a high unburnt carbon content is used as an admixture for concrete, it is desired to reduce the amount of unburnt carbon. So far, at our university, we have developed a technique to remove unburnt carbon by flotation method. It is necessary to add a scavenger and a foaming agent when using this equipment. However, the appropriate amount is unknown. Therefore, we investigated a method to easily estimate the amount of chemicals suitable for flotation treatment from the physical properties of raw fly ash. It is obvious that efficient treatment can be performed when the addition amount of scavenger and the addition amount of foaming agent is set to 10: 1, and that the addition amount of the agent can be accurately estimated by using the methylene blue adsorption amount of fly ash.
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