| 摘要 |
PROBLEM TO BE SOLVED: To obtain an additive which, even when added to a Cr<6+> -containing cemental solidifier reclaimed from industrial wastes, can prevent the solidifier from causing soil pollution by selecting an additive comprising a calcium sulfite powder having a specified solubility when measured by suspending a specified amount of it in a saturated aqueous calcium hydroxide solution and leaving the suspension in a quiescent state. SOLUTION: The calcium sulfite used as an additive for a cemental soil solidifier is a powder having a solubility of 5-100 mg/dm<3> when measured by suspending 0.1 wt.% the sulfite in a saturated aqueous calcium hydroxide solution and leaving the suspension in a quiescent state for 1 hr. The diameter of the powder is 10-40μm. The calcium bisulfite having a solubility in the above range can supply sulfite ions sustainedly for a long term into soil and can therefore satisfactorily prevent Cr<6+> in the cement from causing soil pollution. The calcium sulfite is not limited on its method for preparation and may be, for example, a by-product from waste smoke desulfurization. It is desirable that this additive is used in an amount of about 50 to 150 times the total amount of Cr<6+> in the cement and soil. |
