Fly ash can be used to replace a portion of the portland cement in concrete. In several states, including Oklahoma, increasing amounts of electrical power are being obtained using sub-bituminous coal from western coal fields. This fly ash contains relatively high quantities of lime and and is self-cementitious. Limited data exist on the infiuence of this ash on the characteristics of concrete. One objective of this study was to determine whether fiy ash altered the freeze-thaw resistance of concrete used for paving construction. A second objective was to evaluate the influence of casting temperatures on mix proportions and characteristics of plastic concrete. In both study areas, as much as 50 percent of the portland cement was replaced by fly ash. The purpose of this report is to provide the sponsor with results which have been obtained to date. Some data are yet unavailable for specimens still in curing. In addition, evaluation of the air void system in hardened concrete remains to be accomplished.