報告書番号

V11062

タイトル（和文）

水浸漬による石炭灰中微量物質の溶出性の変化と土工材料への適用に関する基礎検討

タイトル（英文）

Leachability Reduction of Coal Fly Ash with Water Dipping Treatment and Applicability for Geomaterials

概要 （図表や脚注は「報告書全文」に掲載しております）

石炭灰を主原料とした土工材は，長期の強度安定性に優れるとともに，天然材と比較して軽量であるという特徴を持つ。しかし，炭種の多様化によって石炭灰性状の変動が激しくなってくると，環境安全性の面で利用可能な石炭灰の安定的な確保が困難になることが懸念される。そこで，水浸漬処理による石炭灰の溶出性の変化を把握するとともに，土工材料としたときの力学強度と溶出性を検討した。石炭灰を最大半年間脱イオン水・人工海水に浸漬したが，溶媒による溶出性の違いは小さく，概ね浸漬期間の長い石炭灰ほど溶出性は低くなる傾向がみられた。 水浸漬処理した石炭灰を原料にした固化灰は，盛土材として十分な強度を有するとともに，ホウ素，フッ素，六価クロムおよびセレンについて，水浸漬しなかった固化灰よりも溶出性が低く，砒素については同等の溶出性を有することを確認した。

概要 （英文）

Over 1 million tons of coal fly ash (CFA) is used as geomaterials such as aggregates or embankments for a year in Japan. In many case, ash-geomaterials are made by mixed with 5 -20% of cement and they have lower density than natural materials and excellent long-term strength. But it is necessary to ensure the environmental safety because CFA is one of By-products and has some environmental regulated substances. Selecting low-leachability CFAs are one of the solutions. But they are not always obtained the required amount since variable coals are used as fuel. In this paper, we investigated chemical properties of CFAs with water dipping treatment and its applicability for geomaterials. CFAs were dipped in deionized water or sea water up to a half year. Their leachabilities tended to be lowered gradually through the experimental period. CFAs were mixed with 1 – 5% cement and cured for 28 days. The unconfined compressive strengths of fresh CFA mixed with 5% cement (fFC) were 1.4 - 2.5MP. Those of water dipped CFA mixed with 5% cement (dFC) were 1.4 - 1.9 MPa. The leaching amounts of boron, fluoride, chromium (VI) and selenium from dFCs were lower than those from fFCs. Asenic leachability was similar between dFCs and fFCs. fFCs were required rate of 5% addition of cement to meet the environmental quality standards for soil, but dFCs were satisfied with the same criteria with 3% addition of cement.

報告者

キーワード