We Energies Coal Combustion Products ... - The White House

Fly Ash Concrete for Precast/Prestressed
Products
We Energies’ fly ash was also used to produce precast/prestressed concrete
products. We Energies initiated a study to develop mixture proportioning
information for the production of high early strength concrete with high fly
ash content for precast/prestressed concrete products (34).
Materials
The ASTM C-618 fly ash used in this project was produced by We Energies at
the Pleasant Prairie Power Plant. A Type I cement was used and the
replacement quantities with Class C fly ash were 0, 10, 15, 20, and 30%.
Twelve different mixture proportions were developed based upon a nominal
5000 psi control mixture that contained no fly ash.
Concrete Mixing and Specimen Preparation
Concrete was produced at two different precast/prestressed concrete plants.
Standard batching and mixing procedures for ready mixed concrete were
followed, in accordance with ASTM C-94. Fresh concrete tests included
slump and air content. Cylinders were cured following the actual practice of
the individual precast/prestressing plant.
Compressive Strength
The test results indicated that the compressive strength of the concrete
mixtures increased with the increase of replacement percentage of cement
with Class C fly ash after 3 days (5060 psi) and 28 days (8435 psi) of curing.
The maximum compressive strength was obtained for a 25% Class C fly ash
replacement. Therefore, Class C fly ash usage increased the early strength of
concrete. The strength results also indicated that cement replacement with up
to 30% of Class C fly ash increased the early strength relative to the mixture
without fly ash.
Workability
Workability was observed and noted throughout the project. All the concrete
produced was homogeneous and cohesive. The fly ash replacement did not
affect these properties. Slump measurements show variations because of the
use of a superplasticizer. Even though the water to cementitious ratio
decreased as the fly ash was increased, clearly acceptable workability was
maintained.
There are several advantages of using Class C fly ash in the concrete
precast/prestressed products:
117 We Energies
Coal Combustion Products
Utilization Handbook