Production of Lightweight Aggregate from Cindered Sludge of Urban Sewage

Expanded aggregates were experimentally produced from cindered sludge of urban sewage. The cindered sludge itself was not a suitable material for this purpose, but with the aid of over 20% expanded shale it was proved to be possible. When the amount of shale was less than 20%, the pelletizing was very difficult and the expansion property was worse. The experimental results suggested that the pellets had to be fired at 1160°C for 30min. The specifications of lightweight aggregate produced by a test rotary kiln were as follows: (1) the specifie gravity was 1.05, (2) the 24h water absorption was 4.1%, (3) the 28 day compressive strength of the concrete was 352kg/cm2. According to those results, the aggregate produced was acceptable for use in structutal concrete.