| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve the quality at a low cost by mixing a melting point lowering agent, a binder and a foaming agent with a coal ash, pulverizing the mixture to have a specific particle diameter and firing a molding obtained by adding water to the pulverized material in a rotary kiln at a specific temp. to have specific range of bone dry specific gravity. SOLUTION: Bentonite of the binder to be 0.2-5 pts.wt. in external ratio per 100 pts.wt. coal ash, the melting point lowering agent to be 2-6 wt.% in the fired material in total quantity expressed in terms of Na2 O and K2 O and further the foaming agent are added. The resultant mixture is pulverized to have <=15μm average particle diameter. Water is added to the pulverized material to mold and the molding is fired at 1000-1250 deg.C. As a result, a lightweight aggregate having bone dry specific gravity of 1.0-0.5 in is obtained. As the melting point lowering agent, one prepared by mixing sodium carbonate, potassium carbonate and the coal ash, fusing by heating to make vitreous to be 30-50 wt.% in total quantity of Na2 O and K2 and cooling and pulverizing is used.</p> |
