Reuse of UK alum water treatment sludge in cement-based materials

Alum salts are commonly used as coagulants in the purification of surface water for potable supplies. The resultant waste alumina-rich sludge is currently landfilled UK. This study aimed to valorise by using heat-treated alum an additive cement. was calcined at 475–1100 °C and then characterized correlate physical mineralogical changes with cementitious activity engineering performance. 825 transforms poorly crystalline ?-alumina (eta) has activity. rapidly reacts gypsum form ettringite which leads a shortening induction period onset alite hydration. Gypsum depletion undersulfated C3A hydration consumes monosulfoaluminate thereby inhibiting further metastable, transforming highly ?-alumina 1100 °C. In pastes containing more sludges, enhanced because reactions avoided, leading improved