Class F fly ash, when combined with portland cement and hydrated, forms a high-strength material whose strength increases with increasing cement content and compaction effort, and is highest near optimum water content of around 20-30%. However, fly ash in stockpiles can be at a water content of around 50%, so completely drying to optimum water content may not be practical. If the material is left at its stockpile water content, the cement content required to achieve a given strength is about 2.5-3 times higher than the cement content required if compacting at optimum water content. However, strength can be predicted as a function of water content for water contents between the stockpile water content and the optimum water content. (c) 2005 Elsevier Ltd. All rights reserved.