Portland cement, the binder material in traditional concrete for construction applications, is associated with numerous environmental impacts ranging from mining the raw material required for the production of Portland cement, to the large amount of fuel required for extraction and manufacture of the raw product, to the emission of CO2 during actual cement production. A material that resembles Portland cement both chemically and physically is Class C fly ash, which is already being manufactured as a by-product of the combustion of coals to generate electricity at coal-fired power plants. The cementitious nature of fly ash is well documented, and it has routinely been used to replace some of the Portland cement in conventional concrete mixtures. Some fly ashes such as that produced at the Corette power plant in Billings, MT, are sufficiently cementitious to completely replace Portland cement as the primary binder in concrete mixtures. Recent cost increases and shortages of Portland cement have stimulated new interest in the potential of alternate binders of this type. Previous research at Montana State University focused on fly ash available from one source- the Corette Power Plant. This work found that concrete made with Corette fly ash offered exceptional performance in workability, short term strength gain, and long term ultimate strength. Additional work validated the performance of this material in reinforced concrete applications. For this new concrete to be used in commercial applications, however, its durability and the potential cost benefits that it offers need to be further investigated. This project will evaluate remaining performance and cost issues related to using 100 percent fly ash concrete in commercial construction. It will include laboratory testing of material durability, i.e., its resistance to sulfate and hydrogen sulfide, its freeze thaw resistance, and its performance with alkali-silica reactive aggregates. Additionally, full-size precast pieces will be produced at a commercial precast plant.