Coal bottom ash is produced in electrical power stations as a result of coal combustion. Because coal bottom ash and coal fly ash are formed together in the same boiler, similar chemical compositions can be expected. On the other hand, these ashes are of different sizes and shapes. Coal bottom ash is ground in a fashion that it achieves a similar grain size as that of its reference cement. In this study, both ashes were compared from a physical, chemical, and durability point of view to assess the potential use of ground coal bottom ash as a binder in common Portland cements. The compressive strength at 3, 7, 14, 28, and 90 day tests was determined. Ground coal bottom ash mortars displayed a higher level of resistance to natural carbonation and to frost-thaw conditions than the reference mortars with Portland cement without additions. On the contrary, mortars prepared from ground coal bottom ash and/or coal fly ash presented a significant improvement with regard to sulfate attack and alkali-silica reaction.