Conversion to glass-ceramics from glasses made by MSW incinerator fly ash for recycling

Glasses were made using fly ash from municipal solid waste (MSW) incinerators with the addition of SiO2. MgO and TiO2. The glasses were then converted to glass-ceramics for further recycling to construction materials. The optimum heat-treatment schedule for the ceramitization of glasses was 720 degreesC for 90 min for nucleation and 870 degreesC for 10 h for crystal growth. Diopside (CaMgSi2O6) was formed as a major crystalline phase. The glass-ceramics showed good mechanical properties with a hardness of 6.730 MPa, fracture toughness of 1.86 Mpa m(1/2) and bending strength of 127 MPa. Glasses and glass-ceramics with a composition of 20SiO(2)-5MgO-75fly ash-2TiO(2) (all given in wt.%) showed an excellent resistance against leaching of heavy metal ions in water. The amount of heavy metal ions leached after 18 h at 23 degreesC was well below regulation with Cd2+ <0.04 ppm. Cr3+ <0.004 ppm. Cu2+ <0.03 ppm and Pb2+ <0.15 ppm, respectively. (C) 2002 Elsevier Science Ltd and Techna S.r.l. All rights reserved.