Production of glass-ceramics obtained from industrial wastes by means of controlled nucleation and crystallization

Glass-ceramic materials were produced from coal fly ashes obtained from Tunçbilek and Orhaneli thermal power plants in Turkey without or with the addition of red mud from aluminum production and silica fume. The nucleation and crystallization experiments were carried out on the basis of differential thermal analysis (DTA) results to produce glass-ceramic materials. X-ray diffraction (XRD) analysis of the produced glass-ceramic materials revealed that the main crystalline phases were diopside (Ca(Mg,Al)(Si,Al)₂O₆) and aluminum augite (Ca(Mg,Fe³⁺,Al)(Si,Al)₂O₆). The microstructure of the glass-ceramic materials was examined by scanning electron microscopy (SEM). Microstructural observation clearly indicated that the crystallization volume increased when the length of thermal treatment time increased. Glass-ceramic samples produced from industrial wastes had high density and microhardness values with a zero porosity and negligible water adsorption. Toxicity characteristic leaching procedure (TCLP) results showed that the produced glass-ceramic samples are non-toxic materials. Glass-ceramic sample showed high resistance to alkali solutions in contrast to acidic solutions. Overall results indicated that the glass-ceramic samples produced from waste materials with several desirable properties that would make them attractive to industrial use in construction, tiling and cladding applications.