Class C Fly-Ash

Class C Fly Ash can be used as a stand-alone material (because of its self-cementitious properties) or as a product blend. It has been used successfully to improve the strength characteristics of soils achieving superior results for a variety of highway construction projects.

Class C Fly Ash Product Blends

• Enhance soil strength properties
• Stabilize embankments
• Control shrink-swell properties of expansive soils
• Reduce soil moisture contents to permitcompaction

• Density
• Water Content
• Plasticity
• Strength

• Bases
• Subgrades
• Backfill to reduce lateral earth pressures
• Embankments to improve slope stability.

• In-place soil properties
• Delay time
• Moisture content at time of compaction
• Fly ash addition ratio

Fly Ash controls shrink-swell by cementing the soil grains together much like a portland cement bonds aggregates together to make concrete. By bonding the soil grains together soil particle movements are restricted.

Typical addition rates based on dry weight of soil are 8 to 12 percent.

Fly Ash dries the soil by using two basic mechanisms: chemical reactions that consume moisture in the soil and simple dilution. Class C Fly Ash contains tricalcium aluminate (C3A) which is highly reactive with water. C3A is the chemical compound present in ordinary portland cement which is responsible for early strength. The C3A present in fly ash reacts with the water, lowering the overall moisture content of the soil. The drying effect of fly ash in wet soil is immediate, permitting the contractor to quickly proceed with construction. In addition to speeding up the construction process, the use of fly ash provides several other benefits including:

• Making the soil more resistant to additional water infiltration
• Providing additional support for traffic
• Creating a more stable work platform