Performance and evaluation of alum sludge ash as a brick material

Alum sludge needs to be managed properly to ensure its adverse potential impact to environment is mitigated due to its content of pathogen and metal. Usually, alum sludge will be dumped to the landfill for dewatering and become sludge cake due to inadequate facility to treat it. Furthermore, alum sludge treatment involves high cost and handling problem because of its water content and offensive odour. In this study, performance and evaluation of alum sludge ash (ASA) as a brick material was investigated. The alum sludge which was collected was fired to become ash. Ash characteristic (chemical content and mass losses) were investigated by means of Toxicity Characteristics Leaching Procedures (TCLP) and thermogravimetric analysis (TGA). The physical (water absorption and compressive strength) and chemical (leaching) properties mixture of Portland cement with the different weight percentage of alum sludge ash (0% - 40% by mass). TGA analysis showed that 95% of ASA residue remained at temperature 1000°C and the heavy metal contents in the leachate are below acceptable threshold limits. Increasing the ASA contents results in decreased compressive strength and increased water absorption. The result also showed that the mixture 30% of ASA by mass with Portland cement is at optimum condition as a brick material which is comply the standard of bricks.