Valorisation of treated aluminium dross as a pore-forming agent for the development of lightweight sintered artificial aggregate

This study introduces a novel and practical solution to valorise secondary aluminium dross (SAD) as a pore-forming agent in producing lightweight sintered artificial aggregates (SAAs). Two pre-treatment methods involving thermal treatment and water leaching were employed to stabilise aluminium nitride (AlN) in SAD, thereby minimising the ammonia gas emission in the granulation process. The residual AlN in the treated SAD subsequently acted as a pore-forming agent in producing SAAs through its oxidation process. In thermally treated SAD (T-SAD), most AlN oxidised into Al₂O₃, significantly increasing its Al₂O₃ content. In contrast, water leached SAD (W-SAD) underwent the hydrolysis process, resulting in the removal of AlN and the formation of Al(OH)₃. X-ray diffraction analysis confirmed the presence of residual AlN in both T-SAD and W-SAD, while thermogravimetric analysis indicated that the residual AlN could undergo further oxidation, thereby releasing gases at elevated temperatures. SAAs produced by incorporating 30% T-SAD and W-SAD into clay and sintering at 1250°C achieved a bulk density of 768 kg/m³ and 787 kg/m³, respectively, both qualifying as lightweight aggregate (<1200 kg/m³). These findings demonstrate the feasibility of reusing treated SAD as a pore-forming agent in SAAs production, providing a practical pathway for industrial waste valorisation.