2005 Volume 91 Issue 4 Pages 421-427
In order to clarify the possibility of utilization of blast furnace slag containing chlorine, chlorine bearing phases in the synthetic CaO-SiO2-Al2O3-Cl slags were characterized and their dissolution behavior was investigated. The synthetic slags with various crystalinity were identified by XRD and SEM-EDX. Chlorine was found to condense in the amorphous phase and 9CaO·6Al2O3·5SiO2·CaCl2, whereas it was hardly detected in the other crystallized phase, such as CaO·SiO2, 2CaO·Al2O3·SiO2, CaO·Al2O3·2SiO2. The dissolution behavior of chlorine into aqueous solution was studied to grasp the stability of chlorine in the slag. Experimental time (Shaking time) and pH dependences on the solute dissolved from the two main chlorine containing phase, amorphous phase and 9CaO·6Al2O3·5SiO2·CaCl2, were measured. The amount of chlorine dissolved from amorphous phase was smaller than that from 9Ca0·6Al2O3·5SiO2·CaCl2. The amount of solute dissolved from the slag tended to increase with the fraction of crystallization. Furthermore, the crystal phases in blast furnace slags were identified by XRD and SEM-EDX, and there were two main crystal phases, melilite (Ca2(Al, Mg)(Si, Al)2O7) and 9CaO·6SiO2·CaCl2 in it. The similarity between synthetic slag and BF slag was that the amount of Cl dissolved from slag increased with crystallizing.