Investigation was made concerning with a bloating mechanism of water granulated blast furnace slag and the effect of granulating conditions on the density of it. Gases, evolved from molten slag droplets while they were cooled in water, consisted of hydrogen and nitrogen, and also gases existing in the closed pores of the granulated slag mainly consisted of hydrogen and nitrogen of which ratio was of about 1.8. Increase of nitrogen content dissolved in molten slag, made the granulated slag more bloating, and this showed that the dissoved nitrogen causes the evolution of hydrogen and nitrogen gases. Cooling water dissolved into molten slag droplet for a short period until its solidification.
From above mentioned results, it is considered that the bloating of the granulated slag is due to the formation of hydrogen and nitrogen according to the following reaction;
2N 3-+3H2O=3H2+N2+3O2-
Effect of granulating conditions (i.e., water volume, water jet velocity, water temperature and slag temperature) on the apparent specific gravity of the granulated slag was clarified. These conditions influence the reaction time or the reaction temperature for gas forming.
