Self
compacting concrete
The
compaction of concrete is very essential for good compressive strength of
concrete. The voids in concrete id attested and avoided by using better
compaction. But the concrete is poured in congested area the good compaction is
quite difficult. In such places the self compacting concrete to be used.
Because the concrete is need not external compaction. This concrete is compact
itself using self compacting ability
Requirement
of SCC
- Flow ability
- Filling ability
- Segregation resistance
Admixtures
to be added
- Super plasticizers (High range water reducers)
- Viscosity modifying agents
- Air entraining agents
Test
on SCC
The
flow ability and filling ability of self compacting concrete is checked in
laboratory by using following tests
- L box test
- J ring test
- U box test
- V fennel test
- Flow table test
- Compaction factor test
Preparation
of SCC
- Commonly the water cement ratio is high compare to conventional concrete mix. The cement, fine aggregate, course aggregate is taken in correct proportion as per mix design.
- First cement and fine aggregate is mixed properly and add course aggregate then mix evenly.
- Add super plasticizer to the water in required quantity then added to concrete mix. Add half the water. Then mix properly. Then add viscosity modifying agents and air entraining agents to the water then added to the concrete mix.
- Now the VMA is helpful to enhance the concrete flow ability. Also air entraining agent is helpful to prevent air bubble formation in concrete.
- After mixing properly the concrete is pumped and placed in required place with out external compaction.
Advantage
of SCC
- The external compaction is not required
- Workmanship is drastically reduced
- Concrete strength will be increased
- Concrete pouring cost will be reduced
- Construction time will be saved. Quicker construction.
Disadvantages
- Need skilled manpower
- Construction cost is high compare to conventional concrete
- Manual concrete mixing is not possible
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