Sintered glass ceramics from municipal incinerator fly ash

Powder technology, and sintering were used to transform a heavy metal conta ining vitrified municipal incinerator fly ash into glass ceramic products. Highly crystalline and dense products (>95% theoretical density) were fabri cated developing an optimised heat treatment in order to influence the crys tallisation and densification kinetics of powder compacts. The 'best' fabri cated glass ceramic samples were sintered for 6 h at 1000 degrees C after a holding time of 4 it at 880 degrees C. They exhibited a microstructure com posed mainly of elongated crystals of pyroxene type in a residual glassy ma trix. The remaining porosity, was low and limited to small isolated pores. The material showed attractive mechanical properties, i.e. relatively high fracture strength and toughness, very low brittleness index and relatively high thermal shock resistance The products have a large application potenti al especially as construction and building materials. As shown in this stud y some open questions concerning the chemical durability and toxicity of th e products remain, however and they must be fully answered before these gla ss ceramics can be realistically considered for the envisaged applications.