Yasunori Shibata*, Kazuo Ozasa**, Kazuo Tsuzura*** and Hidetoshi Izumi****

* Kawasaki Heavy Industries, LTD.
** Center for Coal Utilization
*** Naruto Salt Mfg. Ltd.
**** Nippon Hodo Co., Ltd.

+ Correspondence should be addressed to Yasunori Shibata:
(1-1 Kawasakimachi, Akashi, Hyogo 673-8666 Japan)

Abstract

About 65% of coal ash is used as raw material for cement, cement mixture material and so on. However, there is a limit in the improvement of availability without processing in coal ash because there are changes in the quality, coal ash is a fine powder, and the leaching of toxic heavy metals exceeds a standard values for utilization. There, the lime-pozzolana reaction characteristic of coal ash was used, coal ash was kneaded with water, and the mixture was processed under saturation steam atmosphere at about 60*C[Celsius degeree], eventually turning into a hardend solid. The hardend solid was crushed and was adjusted in grains of 40mm or less in size. To materialize a large amount of utilization technique as civil materials such as a road base material and so on by granular hardend solid, it was carried out research concerning safety to the environment and stability in quality. It was confirmed that the leaching quantity of toxic heavy metals satisfied the standard value for utilization, and strength of the granular hardend solid improved with the passage of time, for a long term under road base environmental conditions. Furthermore, it was confirmed by actual long term road tests that the granular hardend solid maintained the quality more than the equal to crushed stone to be a representative road base material.

Key words: coal ash, steam treatment, solidified coal ash, stabilization, road base material