Use of Sewage Sludge Ash as Brick Material

Brick manufactured from incinerated sewage sludge ash and clay is investigated. The results of Atterberg limits tests of molded ash-clay mixtures indicated that both plastic index and dry shrinkage decrease with an increasing amount of ash in the mixture. Results of tests indicated that the ash proportion and firing temperature were the two key factors determining the quality of brick. Increasing the firing temperature and decreasing the amount of ash in the brick resulted in a decrease of water absorption. The appropriate percentage of ash content for producing quality bricks was in the range of 20 to 40% by weight with a 13 to 15% optimum moisture content prepared in the molded mixture and firing at 1,000°C for 6 h. With 10% ash content, the ash-clay bricks exhibited higher compressive strength than normal clay bricks. This study showed that the pulverized sludge ash could be used as brick material. The bonding strength can be further enhanced by controlling operating conditions.