3. Self compacting concrete is a flowing concrete mixture
that is able to consolidate under it own weight
The highly fluid nature of scc makes it suitable for
placing in difficult conditions and in section with
congested reinforcement
4. By the early 1990’s, Japan has developed and used scc
that does not require vibration to achieve full
compaction.
As the year 2000, scc used for prefabricated products
(precast members) and ready mixed concrete(cast-in-
situ) in Japan, USA and later on India etc.
5. In 1983,the problem of durability of the concrete
structures was a major topic of interest in Japan.
The creation of durable concrete structures requires
adequate compaction by skilled workers.
Solution for the achievement of durable concrete
structures independent of the quality construction work
is the use of scc.
The necessity of this type of concrete was proposed by
Okamura in 1986.
Present-day scc can be classified as an advanced
construction material.
6. With regard to its composition,scc consists of the same
components as conventionally vibrated concrete, which
are
Cement(OPC 43 OR 53 grade can be used)
Aggregates
Water
Chemical Admixtures i.e., Super plasticizers and
Viscosity Modifying Agents.
Mineral Admixtures i.e., Fly ash, Silica Fume,GGBFS
etc.
7.
8. Give dimensional stability to concrete
The important properties of aggregates is shape and
gradation.
Self- compactability is achievable at lower cement (or
fines)content when rounded aggregates are used. Rounded
aggregates would provide a better flowability and less
blocking potential for a given ware-to-powder ratio.
The presence of flaky and elongated particles may give rise
to blocking problems in confined areas, and also increase
the minimum yield stress
Fillers can be used with aggregates having poor gradation
9. The most important admixtures are the super plasticizers
(high range water reducers),used with a water reduction
greater than 20%.
HRWRAs that work on ‘steric hindrance’require low
dosage as compared to those based on ‘electrostatic
repulsion’.
Acrylic copolymers(AC) and polycarboxylated ethers(PCE)
are effective at lower dosages.
10. Use to improve the stability
Used for underwater concreting in the past.
VMA should be added after the superplasticizers.
11. Fly ash: It reduces free drying shrinkage and restrains
the shrinkage cracking width.
Silica fume: It gives good cohesion, improved
resistance to segregation, also very effective in
reducing or eliminating bleeding.
12.
13. Filling ability:
Slump Flow test & T₅₀ slump flow test.
Passing ability:
L-box , U- box ,J-ring test
Segregation Resistance:
V-funnel test & V funnel at T₅ minutes
14. Slump flow test is used to find the filling ability of the scc.
The scc sample is poured into the slump cone then the
slump flow diameter is measured.
The flow time is measured & that is known as T₅₀ slump
time.
The higher the slump flow value , the greater its ability to
fill formwork under its own weight.
15.
16. The L-Box test is used to find the passing ability of scc.
The scc sample is poured into the L-Box apparatus,
now the plate is removed to allow flow.
The L-Box ratio is calculated as H2/H1.
According to EFNARC , when the ratio of h2 to h1 is
larger than 0.8,self compacting concrete has good
passing ability.
17.
18. The V-Funnel test is used to find the segregation
resistance of scc.
The scc sample is poured into the V-Funnel apparatus
now its allowed to flow by its weight.
The emptying time of V-Funnel is noted.
This test measured the ease of flow of the concrete,
shorter flow times indicate greater flow ability. After 5
minutes of setting, segregation of concrete will show a
less continuous flow with an increase in flow time.
19.
20.
21. Faster costruction
Reduction in site manpower
Better surface finish
Easier placing
Improved durability
Greater freedom in design
Thinner concrete sections
Reduced noise level
Safer working environment
22. More precise measurement and monitoring of the
constituent materials.
Requires more trial batches at laboratory as well as at
ready-mixed concrete plants.
Costlier than conventional concrete based on concrete
material cost (exception to placement cost).
Lack of globally accepted test standards and mix
designs.
23. Self-compacting concrete has been used in bridges and
pre-cast sections.
One of the most remarkable projects built using self-
compacting concrete is the Akashi-Kaikyo Suspension
Bridge, Japan.
The highest use of scc in India was done at Delhi metro
project. About 10000 m³ of scc has been used.
At Kaiga nuclear power plant,scc of characteristic
strength 30MPa was used.