Precast concrete is a concrete product manufactured and cured in a casting facility and then shipped to a jobsite for installation.
As with precast concrete, prestressed concrete is a concrete product manufac- tured and cured in a casting facility and then shipped to a jobsite for installation. Unlike precast concrete prestressed con- crete members undergo additional manufacturing processes i.e. pre-tensioning of the steel strands to increase the load capacity of the element.
What Concrete Properties Are Important In Precast / Prestressed Concrete?
Some of the properties that are important in precast concrete are:
Slag cement can improve each of these properties.
How Does Slag Cement Affect Strength?
Early strengths are important to precast and to prestressed manufacturing. Heat
curing is frequently used in both operations. Slag cement responds well to heat
curing and produces early strengths comparable to, or better than, plain portland
cement mixes. Without heat curing, early strength may be less than plain
portland cement concrete members. Ultimate compressive strengths will be
higher using slag cement. Engineering requirements and plant processes will
influence mix proportions.
Where Are Precast and Prestressed Concrete Products Used?
- Building, housing, landscape, and specialty products
- Sanitary and storm water products
- Water and wastewater products
- Transportation products
- Utility, industrial and farm products
How Does Slag Cement Affect Durability?
Properly proportioned slag cement mixtures produce more durable precast/prestressed
concrete. Slag cement improves durability in the following ways:
- Reduces permeability
- Increases resistance to chloride intrusion, thus improving corrosion resistance
- Reduces susceptibility to sulfate attack
- Mitigates alkali-silica reactivity
By improving the durability of the concrete, the service life of the concrete eleent
may be increased.
How Does Slag Cement Affect Workability?
Slag cement improves the workability of concrete due to its fine grind and glassy
structure. Enhanced workability benefits placing, compaction, and finishing of the
concrete. The resulting concrete elements may have fewer surface voids and
improved consolidation. Slag cement has also been used effectively in the design of
self-consolidating concrete mixtures.
Proportioning Precast/Prestressed Concrete Mixtures with Slag Cement
Precast/prestressed manufacturers who have successfully incorporated slag
cement in their products have used slag cement in ranges from 20 to 50 percent of
How Does Slag Cement Affect Consistency?
Slag cement is one of the most consistent materials used in concrete. Since it is
made in a manufacturing process, chemical composition and particle size are controlled
during its production, ensuring not only conformance with specifications, but
also low variability from shipment to shipment, and even from source to source.
Slag cement does not contain carbon and maintains a consistent particle size, thus
ensuring a stable air void system. Precast manufacturers can depend on slag cement
to help reduce the variability of their concrete
How Does Slag Cement Affect Color?
Slag cement is lighter in color than portland cement. Elements made with slag
cement will therefore have a lighter finished color. The higher the percentage of
slag cement used, the lighter the color will be. This provides greater visibility of the
elements and potentially improved safety.