Self-compacting concrete (SCC) was developed in Japan in the 1980s to solve issues with inadequate concrete compaction. SCC is highly flowable under its own weight and fills formwork without vibration. It was pioneered by Professor Hajime Okamura and has seen increasing use globally since 2000. The document discusses the constituents, properties, testing, and advantages of SCC compared to traditional vibrated concrete.
2. By the early 1990's, Japan has developed and used SCC.
Self compacted concrete is highly engineered concrete
with much higher fluidity without segregation and is
capable of filling every corner of formwork under its self
weight .
Thus SCC eliminates the vibration for the compaction of
concrete without affecting its engineering properties.
As of 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.
3. DEVELOPMENT OF SCC
In 1983, the problem of the 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.
Studies to develop SCC have been carried out by Ozawa and Melawi
at the university of Tokyo.
Present-day SCC can be classified as an advanced construction
material.
4. FATHER OF SCC TECHNOLOGY
Prof.Dr.Hajime Okamura
Developed Self compacting concrete in
1986 in JAPAN.
Currently President of Kochi University
of Technology .
CANMET/ACI AWARD for Outstanding
contributions in the development of SELF
COMPACTABLE HIGH PERFORMANCE
CONCRETE (1995) .
OKAMURA solved the issue of degrading quality of
concrete construction due to lack of compaction by the
employment of SCC which is independent of the quality of
construction work.
5. CONSTITUENTS OF SCC
With regard to its composition, SCC consists of the
same components as conventionally vibrated
concrete, which are
Cement
Aggregates
Water
Chemical Admixtures i.e. Super plasticizers and
Viscosity Modifying Agents
Mineral Admixtures i.e., Fly ash, Silica
Fume, GGBFS etc.
6. TYPICAL MIX PROPORTION
VALUES
Constituent
Typical range by
volume(liter/m3)
Powder
160-240
Water
150-210
Coarse aggregate
270-360
water to powder ratio
0.80-1.10
Fine aggregate
48-55% of total aggregate weight
7. PROPERTIES OF SCC
IN FRESH STATE, SCC HAVE FOLLOWING PROPERTIES-
Filling ability (excellent deformability)
easily at suitable speed into formwork
- flows
Passing ability (ability to pass reinforcement
without blocking) -passes through reinforcements
without blocking
High resistance to segregation- the distribution of
aggregate particles remains homogeneous in both vertical and
horizontal directions
Static segregation due to gravity, vertical direction
Dynamic segregation due to flow, horizontal direction
9. Mechanism for achieving Self Compact
ability (Okamura & Ozawa)
Reduction of
water to
binder ratio
Limitation of
coarse
aggregate
content &
maximum size
High segregation
resistance of
mortar & concrete
Addition of
mineral
admixture
Usage of
Super
plasticizer &
VMA
High Deformability
of mortar &
concrete
Self compactibility
10. MEASUREMENT OF SCC FLOW
PROPERTIES
IN FRESH STATE
Slump Flow & T50 test:
Slump flow test is used to find the filling ability of
the SCC.
The SCC sample is poured in to the slump cone then
the slump flow diameter is measured.
The flow time is measured & that is know as T50
slump time.
The higher the slump flow value, the greater its
ability to fill formwork under its own weight.
14. L-BOX TEST
The L-Box test is used to find the passing
ability of SCC.
The SCC sample is poured in to 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. V-FUNNEL TEST AND V-FUNNEL
TEST AT T5MINUTES:
The V-Funnel test is used to find the Segregation
Resistance of SCC.
The SCC sample is poured in to 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.
20. TESTS ON HARDENED CONCRETE
Compressive Strength Test
Split Tensile Strength Test
Split cylinder test
Standard Beam test
Flexural Strength Test
Preparation of SCC specimens:
All the materials are placed in the mixer & mixed well
The sample is taken out and poured in to the moulds.
The moulds are socked in water & allowed for curing .
21. ACCEPTANCE CRITERIA FOR SCC IN FREE STATE
Test Results on Fresh Concrete and Acceptance Criteria for SCC
S. No
Method
1
Slump
Flow
Test
Unit
Water/Cement Ratio
0.23
0.24
0.25
0.26
EFNARC[3]
0.27
Specification
Remarks
SF1: 550-650
mm
655
660
665
680
700
SF2: 660-750
SF2
SF3: 760-850
VS1: T500 ≤ 2
2
T500
sec
3.94
3.88
3.82
3.32
2.50
3
V-Funnel
sec
8.50
8.35
8.10
7.95
6.89
VF1: ≤ 8
4
T5min
sec
11.89
10.92
10.66
10.23
9.95
VF2: 9-25
5
L-Box
h2/h1
0.950
0.959
0.969
6
U-Box
mm
9
7
6
0.975 0.980
5
4
VS2: T500 > 2
PA1: > 0.8
(2 rebars)
PA2: > 0.8
(3 rebars)
0-30 [23]
VS2
VF2
PA2
OK
23. DISCUSSION ON TEST RESULTS
Based on the above experimental results, the observations are as follows:
Slump flow increases with the increase of water/cement ratio.
T500 time, V-funnel time, T5 time and U-box values are decreases with
the increase of w/c ratio.
L-box
value increases with the w/c ratio and Compressive
strength, tensile
strength and flexural strengths are decreasing as
the w/c ratio increases.
Marginal increase in the compressive strength at 28 days of concrete as
the w/c ratio decreases.
Compressive strength and split tensile strength decreases at higher
rate for 7 days strength when compared to 28 days strength, whereas
it is also observed that flexural strength value decreases at higher rate
for 28 days strength when compared to 7 days strength.
24. ADVANTAGES OF SCC
Elimination of problems associated with vibration.
Faster construction
Improves working conditions and productivity
in
construction industry.
Greater freedom in design.
Less noise from vibrators and reduced danger from
hand-arm vibration syndrome (HAVS).
Ease of placement results in cost savings through
reduced equipment and labour requirement.
Improves the quality, durability, and reliability of
concrete structures due to better compaction and
homogeneity of concrete.
Reduced wear and tear on forms from vibration.
Reduced permeability.
25. DISADVANTAGES OF SCC
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
More stringent
requirements on the
selection of materials .
26. CONCLUSION
SCC has high potential for greater acceptance and wider applications in highway
bridge construction in the all over world. An NCHRP Research Project has been
initiated to develop design and construction specifications to supplement the
AASHTO LRFD Bridge Design and Construction Specifications.
Based on above results
conclusions are drawn-
and
discussions
the
following
Self Compacting Concrete (SCC) technology can save
time, cost, enhance quality, durability and Moreover it is a
green concept.
Since the concrete is capable of self-consolidating and
reaching the difficult areas in moulds, manual variables in
terms of placing and compacting concrete is nil. This factor
ultimately yields defect less, better-quality concrete
structures.
Cast-in-place concrete construction in tight space and
congested reinforcement, such as, drilled shafts, columns and
earth retaining systems, can be accelerated by using SCC.
27. REFERENCES
1.
Brain Paulson. EFNARC, Secretary General, „Specifications and Guidelines for
Self-Compacting Concrete”, February 2002.
2.
Nan Su, K.C. Hsu, H.W. Chai. A Simple mix design method for self-compacting
concrete, cement and concrete Research 2001.
3.
3.Okamura.H.„Self-Compacting
High
Performance
International, Vol. 19, No.7, pp. 50-54, July 1997
4.
4. M.S. Shetty. “Concrete technology (theory and practice), S. Chand & Company
LTD. 2002
5.
IS 456-2000 Code of practice for plain and reinforced concrete (3rd
6.
16. IS 516-1959 Method of test for strength of concrete
7.
SK Singh “Self Compacting Concrete - A Paradigm Shift”, Journal of New Building
Materials & Construction World, Vol. 15, No. 3, pp 164-180,September , 2009.
Concrete‟,
Concrete
revision)