フライアッシュの基礎性状と高温加熱挙動― フライアッシュ人工骨材 (第 1 報) ―

The investigations on artificial aggregate from coal fly ash have been continued long time, and a few productions are realized. Mass production of aggregate that has stable quality has been uneasy, because the electric power plants in Japan use many kinds of coal, and chemical compositions and unburned coal contents of the fly ashes are not uniform. Low water absorption and high strength are indispensable for aggregate for concrete. In view point of production, stability in quality is desirable against firing temperature change. In order to produce an aggregate of stable quality from different fly ash, authors have studied on properties of the fly ashes, pellets fired in rotary kiln and the concrete using fired pellet (aggregate). Some relations between physico-chemical properties of 24 fly ashes and its fired behaviors are reported herein. As a result, fly ashes were divided into two groups： one reached highest density at the temperature less than 1,200°C (low temperature group), the other at higher than 1,250°C (high temperature group), reflecting their chemical and mineralogical compositions. The former is mainly sintered by the presence of univalent K as a flux and the latter is sintered by divalent Ca, Mg adding to K. Plagioclase consisted in the former and cristobalite in the latter as a prominent mineral of sintered body. Hemisphericalizing temperature correlated to mullite content, and degree of densification corresponded to glass content. Compressive strength roughly depended on specific gravity of sintered body.