Welsh Fly Ash Used in DFW Expansion
Fly ash from AEP’s Welsh Power Plant, located
near Pittsburg, Texas, is being used as a pozzolan in
the concrete being poured for terminal expansion work
at the Dallas/Fort Worth Airport.
ISG Resources, Inc.,
the plant’s CCP marketer, is providing the technical and logistical
support required for the project.
Fly ash used as a pozzolan or partial replacement for
cement in concrete, provides for:
- Higher Strength. Fly ash continues to combine with
free lime, increasing structural strength over time.
- 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
- Increased 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, soft (lime hungry)
water, and seawater.
- Reduced Sulfate Attack. Fly ash ties up free lime
that can combine with sulfate to create destructive expansion.
- Reduced Efflorescence. Fly ash chemically binds
free lime and salts that can create efflorescence
and dense concrete holds efflorescence producing
compounds on the inside.
- Reduced Shrinkage. The largest contributor to drying
shrinkage is water content. The lubricating action of
fly ash reduces water content and drying shrinkage.
- Reduced Heat of Hydration. The pozzolanic reaction
between fly ash and lime generates less heat, resulting
in reduced thermal cracking when fly ash is used to
replace portland cement.
- Reduced Alkali Silica Reactivity. Fly ash combines
with alkalis from cement that might otherwise combine
with silica from aggregates, causing destructive expansion.
- Workability. Concrete is easier to place with
less effort, responding better to vibration to fill forms more completely.
