This study has been carried out on castable and matrix of a magnesia-based unshaped refractory system containing respectively 5.0% and 20.0% graphites. The graphite has been incorporated either as uncoated or surface-modified form, the latter containing a thin sol-gel calcium aluminate film over graphite surface. Surface modification of graphite has been confirmed by scanning electron microscopy, X-ray diffraction, Raman spectra, Fourier transformed infrared study and some other experiments. The sol-gel coating improved hydrophilicity and oxidation resistance of graphite. Sinterability, thermal and thermomechanical properties of castable matrices have been elaborately documented. From this work it is apparent that presence of coated graphite in matrix part of basic castable is not that encouraging as observed in alumina-carbon system. However, the castable properties as a whole are satisfactory due to protection of graphite and its less water demand for casting. © 2017 Indian Ceramic Society.