Use of metakaolin to stabilize sewage sludge ash and municipal solid waste incineration fly ash in cement-based materials

► Metakaolin was used to help immobilizing industrial wastes in cement-based materials. ► A dilution process (i.e. reduction of waste content) was tested and discussed. ► The solid residues had no significant effects on functional of cement-metakaolin mortars. ► Metakaolin was beneficial in decreasing the leaching of heavy metals.