Approximately 14,000 tons of fly ash from AEP’s Rockport Power Plant, located near Rockport, Indiana, was used as a pozzolan in the concrete poured for the reconstruction of I-70 in Clark County, Indiana. LaFarge North America, the plant’s fly ash marketer, is providing the technical and logistical support required for the project.

Rockport Fly Ash Used in I-70 Reconstruction

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.