Japan has used self-compacting concrete (SCC) in bridge,
building and tunnel construction since the early 1990.s. In the last five years, a
number of SCC bridges have been constructed in Europe. In the United States,
the application of SCC in highway bridge construction is very limited at this time.
However, the U.S. precast concrete industry is beginning to apply the technology
to architectural concrete. SCC has high potential for wider structural applications
in highway bridge construction.
The application of concrete without vibration in highway bridge
construction is not new. For examples, placement of seal concrete underwater is
done by the use of a tremie without vibration, mass concrete has been placed
without vibration, and shaft concrete can be successfully placed without vibration.
These seal, mass and shaft concretes are generally of lower strength, less than
34.5 MPa and difficult to attain consistent quality. Modern application of selfcompacting
concrete (SCC) is focused on high performance . better and more
reliable quality, dense and uniform surface texture, improved durability, high
strength, and faster construction.
Recognizing the lack of uniformity and complete compaction of
concrete by vibration, researchers at the University of Tokyo, Japan, started out
in late 1980.s to develop SCC. By the early 1990.s, Japan has developed and
used SCC that does not require vibration to achieve full compaction. More and
more applications of SCC in construction have been reported in Japan. As of the year 2000, the amount of SCC used for prefabricated
products (precast members) and ready-mixed concrete (cast-in-place) in Japan
was about 400,000 m3.
DEVELOPING SCC MIXES
SCC mixes must meet three key properties:
1. Ability to flow into and completely fill intricate and complex forms under its
2. Ability to pass through and bond to congested reinforcement under its own
3. High resistance to aggregate segregation.
The SCC mixes are designed and tested to meet the demands of the projects.
For example, the mix for mass concrete is designed for pumping and depositing
at a fairly high rate. SCC was used in the construction of the anchorages of the
Akashi-Kaikyo Suspension Bridge.
The SCC was mixed at a batch plant at the job site and pumped through a piping
system to the location of the anchorages 200 m away. The SCC was dropped
from a height of as much as 5 m without aggregate segregation. For mass
concrete, the maximum size of coarse aggregates may be as large as 50 mm.
The SCC construction reduced the construction time for the anchorages from 2.5
years to 2 years. Similarly, SCC mixes can be designed and placed successfully
for concrete members with normal and congested reinforcement. The coarse
aggregate size for reinforced concrete generally varies from 10 mm to 20 mm.
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