Fly ash, a supplementary cementitious material (SCM), is an important constituent in the production of concrete. Although demand for SCMs is increasing, the amount of fly ash produced by coal-fired power plants is decreasing, and so the transportation industry is looking for viable alternatives to traditional fly ash that can provide reliable performance. These alternatives, which include  nontraditional or off-specification fly ash as well as other SCM sources, are promising because of their abundance and potential economic value. Three projects supported through the Federal Highway Administration’s (FHWA) Exploratory Advanced Research (EAR) Program seek to study and document how the chemical and physical properties of these alternative materials affect the performance of concrete. These projects aim to provide State Departments of Transportation with information that describes how these materials affect the durability, sustainability, and strength of concrete so that engineers can make informed and timely decisions regarding materials specifications and concrete mixture performance criteria.