Abstract :
Self-compacting
concrete (SCC) is an innovative concrete that does not require vibration for
placing and compaction. It is able to flow under its own weight, completely
filling formwork and achieving full compaction, even in the presence of
congested reinforcement. The hardened concrete is dense, homogeneous and has
the same engineering properties and durability as traditional vibrated
concrete.
Self-compacting
concrete offers a rapid rate of concrete placement, with faster construction
times and ease of flow around congested reinforcement. The fluidity and
segregation resistance of SCC ensures a high level of homogeneity, minimal
concrete voids and uniform concrete strength, providing the potential for a
superior level of finish and durability to the structure. SCC is often produced
with low water-cement ratio providing the potential for high early strength,
earlier demoulding and faster use of elements and structures.
The elimination of
vibrating equipment improves the environment on and near construction and
precast sites where concrete is being placed, reducing the exposure of workers
to noise and vibration.
The improved
construction practice and performance, combined with the health and safety
benefits, make SCC a very attractive solution for both precast concrete and
civil engineering construction.
Self-compacting
concrete and traditional vibrated concrete of similar compressive strength have
comparable properties and if there are differences, these are usually covered
by the safe assumptions on which the design codes are based. However, SCC
composition does differ from that of traditional concrete so information on any
small differences that may be observed is presented in the following sections.
Durability, the
capability of a concrete structure to withstand environmental aggressive
situations during its design working life without impairing the required
performance, is usually taken into account by specifying environmental classes.
This leads to limiting values of concrete composition and minimum concrete
covers to reinforcement.
In the design of
concrete structures, engineers may refer to a number of concrete properties,
which are not always part of the concrete specification. The most relevant are:
Compressive strength
Tensile strength
Modulus of elasticity
Creep
Shrinkage
Coefficient of thermal
expansion
Bond to reinforcement
Shear force capacity in
cold joints
Fire resistance
Where the value and/or
the development of a specific concrete property with time is critical, tests
should be carried out taking into account the exposure conditions and the
dimensions of the structural member.
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