2g
2 2g
2g
RWI- It reduces congestion at the site and prevents traffic jams.
- It hastens infrastructure development and thus provides more employment opportunities.
- It is an environmentally safer alternative.
- With ready mixed concrete, modern construction techniques can be followed.
- Convenience—Ready Mix Concrete is delivered at the site with minimum logistical
hassles. - Different types of concretes can be made for different applications.
- Use of RMC obviates the need to set up the infrastructure required for site manufactures
of concrete. This also reduces the working capital to be invested by the customers, as they
will not be required to maintain stock of aggregates, cement, plant and machinery etc.
PHIT ivpEgywegsxq2gyxgii
Self-Compacting concrete (SSC) first introduced in Japan is a very special type of concrete
which can flow and fill into every corner of formwork, even in the presence of congested
reinforcement, purely by means of its own weight and without the need of vibrating compaction,
tamping etc. Self-Compacting concrete as it sounds is nothing different from normal concrete.
It is just usage of extra admixtures (super plasticizers and viscosity modifying admixtures) and
different amounts of composite materials that makes SSC act different to normal one. In SSC,
high amount of supplementary cementitious materials, up to 70% of the total powder content,
are added. Normally these supplementary materials are fly ash, silica flume, blast furnace slag
etc. Since SSC does not require any compaction, it saves time, labour and energy. Also, good
surface finish is produced.
Self-Compacting concrete is characterized by high powder content. The parameter that is
important in SSC is water-powder ratio, water-cement ratio is completely ignored. Other
important parameters are fly ash content, sand-aggregate ratio, paste percentage, types of
admixture used. etc. The aggregate content in SSC is smaller than that for conventional concrete
requiring vibration.
The degree of packing of coarse aggregate in SSC is approximately 50%. It is to reduce the
interaction between coarse aggregate particles when the concrete deforms. The degree of
packing of fine aggregate in SSC mortar is approximately 60% so that the shear deformability
when the concrete deforms may be limited. On the other hand, the viscosity of the paste in SSC
is highest among the various types of concrete due to is lowest water-powder ratio. This
characteristic is important in inhibiting segregation.
The comparison of mix proportion between Self-Compacting concrete and normal
conventional concrete is shown in Table 20.9.
2PHW
2%2
2)
2 "2% +
% x2g %Eg
"2g
E<2
H/QS@H/SS H/QS/RS
2
22H/QS
22H/RS
p 2!2 w 22w 22
2
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