In this study sinterability of the two class F fly ashes were investigated as a function of sintering temperature and sintering time. For this aim, Catalagzi and Sugozu thermal power plant fly ashes resulted from burning of bituminous coals were first pressed into cylindrical specimen, and then sintered to form ceramic materials without the addition of any materials like organic binders or inorganic additives. Sintering efficiency was evaluated in terms of ceramic specifications such as density, water absorption, shrinkage and splitting tensile strength. Furthermore, phase developments and microstructural changes due to sintering process were determined with X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. Overall results have shown that Sugozu fly ash seems to have better sintering properties than Catalagzi fly ash due to the better microcrystalline structure, higher density and strength with the lower porosity, water absorption and shrinkage values. (C) 2012 Elsevier Ltd. All rights reserved.