PORTLAND CEMENT CONCRETE - Materials for Civil and Construction Engineers - page 295

Polymer concrete is a mixture of aggregates and a polymer binder. There
are a wide variety of polymers that can be mixed with aggregates to make
polymer concrete. Some of these can be used to make rapid-setting concrete
that can be put in service in under an hour after placement. Others are for-
mulated for high strength; 140 MPa (20,000 psi) is possible. Some have good
resistance to chemical attack. A common characteristic is that most polymer
concretes are expensive, limiting their application to situations in which
their unique characteristics make polymer concrete a cost-effective alterna-
tive to conventional concrete.
Polymer-portland cement concrete incorporates a polymer into the pro-
duction of the portland cement concrete. The polymer is generally an elas-
tomeric emulsion, such as latex.

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7.6.9 Fiber-Reinforced Concrete

The brittle nature of concrete is due to the rapid propagation of microc-
racking under applied stress. However, with fiber-reinforced concrete, fail-
ure takes place due to fiber pull-out or debonding. Unlike plain concrete,
fiber-reinforced concrete can sustain load after initial cracking. This effec-
tively improves the toughness of the material. In addition, the flexural
strength of the concrete is improved by up to 30%. For further information
on the design and applications of fiber-reinforced concrete, consult the ACI
Guide for Specifying, Mixing, Placing and Finishing Steel Fiber Reinforced
Concrete .
Fibers are available in a variety of sizes, shapes, and materials (Figure
7.45). The fibers can be made of steel, plastic, glass, and natural materials.
Steel fibers are the most common. The shape of fibers is generally described
by the aspect ratio, length/diameter. Steel fibers generally have diameters
from 0.25 mm to 0.9 mm (0.01 in. to 0.035 in.) with aspect ratios of 30 to
150. Glass fiber elements' diameters range from 0.013 mm to 1.3 mm (0.005
in. to 0.05 in.).

FIGURE 7.45 Fibers used for fiber-reinforced concrete