Alkali activated solidification/stabilisation of air pollution control residues and co-fired pulverised fuel ash

► Solidification/stabilisation of APC residues using waste PFA and waste alkali shows some promise. ► Chloride leach remains a problem, but cast monoliths remained cohesive during leach testing. ► The use of waste pfa, with a high sulphur content, could lead to problems with sulphate release. ► Solvent ion effects meant that sulphate release was strongly dependent on chloride release.