Poster (EARTH)

[PE1-059] Effect of Iron Salt Amendment on Lightweight Aggregate Formation

○Yu-Ling Wei¹, Shao-Hsian Cheng¹ (1. Tunghai University)

Keywords:Lightweight aggregate, Coal fly ash, Sintering, Flux

F-class Coal fly ash is light grey in color, limiting its application in cement industry in Taiwan. An alternative treatment approach is to recycle it as lightweight aggregates for construction sector. In lightweight aggregate preparation, iron oxide is always considered as flux components, yet effect of iron forms on flux enhancement has not been studied so far. Along with glass, various iron salts were added in the coal fly ash to serve as raw materials for lightweight aggregate preparation through sintering at > 1000 ^oC. After sintering, the fired pellets were investigated in both physical and chemical properties. Results indicate that all various iron salts can considerably lower sintering temperature, saving energy for the high-temperature process. In aspect of 24-hour water sorption rate of the fired pellets, the ones added with ferric sulfate is more desired for construction section than ferrous chloride because the former pellets sorb less water, 9-13 percent, than the latter one, 13-20 percent, implying a better workability for concrete preparation consisting of cement, lightweight aggregate, sand, and water. The particle density of all fired pellets is < 1.5 g cm^-3, meeting the construction criterion < 2.0 g cm^-3. In fact the sintering temperature can be lowered by approximately 75 ^oC, as compared to the control raw materials. The level in decrease of pellet crystalline phases after firing is slightly greater for ferrous chloride-added pellets. The decrease in crystallinity is accompanied by an increase in formation of glassy surface that benefits bloating of the fired pellets. Wollastonite, diopside, and crystabolite develop as new phases in all fired pellets. For the eight regulatory toxic metal leaching, all fired pellets meet Taiwan legal limits.