抄録
The authors prepared various oolitics sand by coating Na and Ca bentonite oven silica sand within 4∼16 mass % and burning it at 1273 K. According to the specific gravity and water absorption quantity of ootitics, it was calculated that oolitics had a 5∼15 vol % void which absorbs water. According to the change of the grain fineness number, that the average oolitics thickness was calculated to be 4∼7μm. The authors prepared green sand by adding bentonite to oolitics sand. Green sand properties such as moisture, test piece density, dry compression strength, maximum expansion and scabbing time changed in proportion to the oolitics quantity. Green compression strength and surface stability were increased by adhering oolitics, however the ratio was low when more oolitics adhered. The authors have arrived concluded that oditics affected the properties of green sand due to (a) Water absorption to void part, (b) Decrease of bulk specific gravity, (c) Increase of friction resistance, (d) Granulation, (e) Expansion absorption.
