High-temperature concrete binders in which fly ash, as environmentally harmful secondary raw material, is combined with masonry and refractory cement is a new option for reapplication of this coal combustion by-product. In this study, the design of the bonding agents was based on the fly ash from lignite coal combustion process and two types of cement: Portland cement and aluminate cement. Fly ash was applied without any further mechanical or thermal treatment. Mechanical properties of the binders were investigated and subsequently correlated with changes which occurred in the phase composition and microstructure of the agents. Scanning electron microscopy was used in investigation of microstructural changes caused by temperature. X-ray diffraction method was used in monitoring of the mineral phase changes also induced by increasing temperature. The investigations conducted on the bonding agents highlighted presence of good refractory properties and temperature-resistance, and also showed high values of compressive strength. The investigated bonding agents, thus, can be applied in refractory concretes, but also in various types of thermo-insulations.