Shortly following the award of a Contract that included a large RCC dam, on mobilization to the site it was realized by the stake holders that the use of fly ash was prohibited, as recent legislation had banned import and transport of fly ash in Jordan. The ban has been imposed due to environmental concerns. The project needed to come up with a suitable replacement for fly ash that was not only cost effective but also met the project design construction conditions, including temperatures exceeding 35-degrees Centigrade for most of the year. The RCC mix design was also required to meet other design criteria such as strength and water tightness. This paper presents the structured program implemented to arrive at the most suitable RCC mix design. RCC dam construction on the project has commenced.