Advantages
- Higher Strength: Fly ash continues to combine with free lime, increasing compressive strength over time.
- Reduced Segregation: Improved cohesiveness of fly ash concrete reduces segregation that can lead to rock pockets and blemishes.
- Decreased Permeability: Increased density and long term pozzolanic action of fly ash, which ties up free lime results in fewer bleed channels and decreases permeability.
- Increase Durability: Dense fly ash concrete helps keep aggressive compounds on the surface, where destructive action is lessened. Fly ash concrete is also more resistant to attack by sulfate, mild acid and seawater.
- Reduced Bleeding: Fewer bleed channels decrease permeability and chemical attack. Bleed Streaking is reduced for architectural finishes.
- Reduced Sulfate Attack: Fly ash ties up lime that can combine with sulfate to create destructive expansion.
- Reduced Heat of Hydration: The pozzolanic reaction between fly ash and lime generates less, resulting in reduced thermal cracking when fly ash is used to reduce Portland cement.
- Improved finishing: Sharp, clear architectural definition is easier to achieve, with less worry about in-place integrity.
- Reduced Efflorescence: Fly ash chemically binds free lime and salts that can create efflorescence, and dense concrete holds efflorescence producing compounds on the inside.
- Workability: Concrete is easier to place with less effort, responding better to vibration to fill forms more completely. Fly ash generally reduces the water demand for required concrete slump.
- Reduced Alkali Silica Reactivity: Fly ash combines with alkalis from cement that might otherwise combine with silica from aggregates, causing destructive expansion.
- Ease of Pumping: Pumping requires less energy and longer pumping distances are possible.