Yasuhiko Yamamoto

A STUDY ON THE METHODS OF EVALUATING THE FINENESS OF GROUND GRANULATED BLAST-FURNACE SLAG

Adequate methods for evaluating the fineness of ground slags were sought using various slag samples which were prepared by grinding three granulated slags by either a jet mill or ball mill to about 3000-8000cm2/g Blaine surface. It was confirmed that the conventional Blame air permeability method could be employed to evaluate the relative fineness of ground slags, provided that their raw materials and grinding mill were maintained the same. A proposal was made to select the amount of sample for the Blaine method in such a way that its sample bed could be formed with a force of 3-5kgf. As an index for evaluating the fineness of all kinds of ground slags, the specific surface areas calculated from their particle size distributions, which were analyzed by a laser-beam method, were considered to be most appropriate.

ALKALI-SILICA REACTIVITY OF FERRO-NICKEL SLAGS

Experiments were conducted to generally clarify the alkali-silica reactivity of ferro-nickel slags. The slag samples tested include one slag that was found to be most reactive in the previous study, three samples prepared by reheating the most reactive slag up to 700, 1000 or 1100°C, and one glassy slag. The slags which were composed of only forsterite and glassy phase and contained little CaO as their compositions were found to be reactive. In the case of these slags, amorphous silica in them was considered to be responsible for their reactivity. When about 15% CaO existed in slag, the dissolution of silica in alkali solution was greatly suppressed, thereby making the slag innocuous. The reactive slag could be converted to innocuous one by reheating it to 1100°C. Replacing a part of cement with such mineral fines as fly ash and blast furnace slag was quite effective in reducing the expansion of concrete due to alkali-silica reaction.