A study on cooling condition and structure of ferro nickel slag. Cooling condition for prevention of alkali-aggregate reaction.

Abstract

The effect of the cooling condition of molten ferro-Ni slags on retained glass and cryst. phases (enstatite, forsterite, cristobalite) was discussed. Crit. cooling rate for glass formation was 20-120.degree./s, which depended on SiO2 content in the ferro-Ni slags. Forsterite, enstatite, and cristobalite were crystd. from the molten slags in that order on decreasing the continuous cooling rate. The 1st cryst. phase obsd. by isothermal heating of slags in a olivine primary phase in a FeO-MgO-SiO2 system was forsterite, whereas forsterite and enstatite were obsd. by isothermal heating of a slag in a pyroxene-olivine ***eutectic*** phase. Enstatite and cristobalite gradually increased with increasing the holding time of the heating. Slow cooling of the molten slags to transform the glass phase to desired cryst. phases was recommended for prevention of alkali-aggregate reactions when the slags were used for concrete.