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In recent years, self compacting concrete has gained wise used for placement in congested reinforced concrete structures with difficult casting conditions. For such application, fresh concrete must posses high fluidity and good cohesiveness. The use of fine materials such as class F flyash can ensure the required concrete properties. Self Compacting Concretes flows under its own weight and fills into every corner of form work and passes through even restricted spacing of highly congested reinforcement. Self Compacting Concrete compacts by itself without the need of vibration.
An experimental investigation is undertaken for Self Compacting Concrete with mix M3 which are designed equivalent to grades of M30. The water cement ratio of 0.35 is The workability characteristics of Self maintained constant. The Self Compacting mixture had a cement replacement of 30%. Fairflo 100(M), Carboxylic ether polymer based superplasticizer with a dosage of 1.2% of powder (Cement + 30% flyash + 10% silica fume).
Compacting Concrete such as filling ability, passing ability, and segregation resistance are thoroughly understood with Slump flow test, L-box test, and V-funnel test.
2.0 General Introduction :
The development of development of Self Compacting Concrete (SCC), a much-needed revolution in concrete industry. Self Compacting Concrete is highly engineered concrete with much higher fluidity without segregation and is capable of filling every corner of formwork under its self-weight only (1). The SCC eliminates the need of vibration either external or internal for the compaction of concrete without compromising its engineering properties (2).
This concrete was first developed in Japan in late 1980's to combat the deterioration of concrete quality due to lack of skilled labours along with concerns regarding the homogeneity and compaction of cast in place concrete within intricate structures for improvement of durability quality of concrete (3). After the development of SCC in Japan 1988 whole Europe started working on this unique noise free revolution in the field of construction industry. The last half of decade 1990-2000 has remained very active field of research in SCC concrete in Europe. That is why, Europe has become ahead from USA in Publishing specification and guidelines for Self Compacting Concrete. Now, all over the world a lot of research is going on, how to optimize the fluidity of concrete with its strength and durability properties without a drastically increase in the cost. The first North American conference on design and use of SSC was organized in November 2002. However, at present many researches are being carried out in numerous universities and government R & D organizations due to benefits of the use of this concrete.
2.1 Advantages of Using SSC :
Some of the important advantages that are commonly experienced by adopting SCC are as follows
SCC yields homogeneous concrete in situations where the castings are difficult due to congested reinforcement, difficult etc.
SCC shows a good filling ability especially around reinforcement.
Reduces noise at sites, the precast factory, and neighborhood; hence, it is a silent concrete.
Eliminates problems with blood circulation leading to "white fingers" caused by compacting equipment, hence called healthy concrete.
Shortens the construction time by accelerating construction process, especially in precast industry.
Its ease of placement improves the productivity and the cost saving through reduced equipment and labour equipment.
Reduction in wear and tear of forms, therefore, it extends the service life of forms.
Reduction in the number of worker. Normally one cum requires 1.5 man-hours; with SCC this is reduced to 0.35 man-hours.
Shows narrow variation in properties on site.
It reduces the consumption of resources and cost, even considering a higher price per cubic meter for the concrete
2.2 Disadvantages of SCC :
The production of SCC places more stringent requirements on the selection of materials in comparison with conventional concrete.
An uncontrolled variation of even 1% moisture content in the fine aggregate will have a much bigger impact on the rhelogy of SCC at very low W/C (0.3) ratio. Proper stock piling of aggregate, uniformity of moisture in the batching process and good sampling practice are essential for SCC mixture.
A change in the characteristics of a SCC mixture could be a warning sign for quality control and while a subjective judgment, may some times be more important than the quantitative parameters.
The development of a SCC requires a large number of a trial batches. In addition to the laboratory trial batches, field size trial batches should be used to simulate the typical production conditions. Once a promising mixture has been established, further laboratory trial batches are required to quantity the characteristics of the mixture.
SCC is costlier than conventional concrete initially based on concrete materials cost due to higher dosage of chemical admixtures, i.e. high range water reducer and viscosity enhancing admixture (VEA). Increase in material cost can be easily offset with improvement in productivity, reductions in vibration cost and maintenance and proper uses of mineral admixtures.
2.3Applications in Precast Concrete Industry :
In the precast concrete industry SCC was welcomed as a considerable step forward. Many producers now use SCC for a considerable part of their production and some have even changed to 100% to SCC. The advantages are convincing.
SCC the vibration level is reduced from the range of 0.75 - 4.0 m/s2 to zero.
Dust :By the introduction of SCC, the dust concentration can be reduced to a value as low as 0.2 mg/m3.
SCC is slightly expensive than conventional concrete as per European Standards3. On the other hand there are considerable savings.
Summing up all those advantages it is calculated that the cost of production decreases by the introduction of SCC and the labour conditions and the quality of the finished products improve.
2.4 Working Program
A total of 108 cubes of 150mm side, 18 prism of 100mm x 100mm x 500mm and cylinder of 100mm dia, 200mm height of Self Compacting Concrete and conventional concrete are cast. Test were carried out on all mixture to study the rheological properties.
Compressive strengths @ 1 days, 3 days, 7 days, 14 days, 21 days & 28 days are recorded for Self Compacting Concrete & Conventional Concrete, where as split tensile strength test and Flexural Strengths test are tested after 28-days curing.
9 beams of size 2300mm x 150mm x 230mm, number of beams each for self compacting reinforced concrete for mix M3 & number of beam each for conventional reinforced for mix M30 are cast.
The result shows that an economical Self Compacting Concrete could be successfully developed by incorporating 30% class F fly ash & 10% Silica fume
3.Workability Characteristics of SCC
A concrete can be classified as self-compacting concrete only when the requirements such as filling ability, passing ability and segregation resistance are fulfilled(5) - table 1.
3.1 Filling ability (excellent deformability)
3.2 Passing ability (ability to pass reinforcement without blocking)
3.3 High resistance to segregation
3.1 Filling Ability :
Self compacting concrete must be able to flow into all the spaces within the formwork under its own weight. This is related to workability as measured by slump flow.
3.2 Passing Ability :
Self compacting concrete must flow through tight openings such as spaces between steel reinforcing bars under its own weight. The mix must not 'block' during placement.
3.3 High Resistance to Segregation :
Self compacting must meet the requirements of 3.1 and 3.2 while its original composition remains uniform. The key properties must be maintained at adequate levels for the required period of time (e.g. 20 min.) after completion of mixing. It is property 3.2 the passing ability and property 3.3 resistance to segregation that constitute the major advance from a merely super elasticized fresh mix which may be more fluid than self compacting concrete mix.
3.4.5 Tests to be fulfilled to qualify as SCC :
Though there are many test methods to confirm the qualification to SCC, as mentioned above, no single method or combination of methods have obtained universal acceptance.
So any mix aimed to be SCC must be tested for at least three workability tests. These can be a combination of any of the following, in addition to slump flow test, V-funnel test, L-box blocking ratio test and U-box test etc.(11).
Typical range of values
Slump flow by Abrams cone
T50cm slump flow
Time increase, V-funnel at T5minutes
GTM screen stability test
Table No 1 Suggested value of acceptance for different test
4. Experimental Programme
4.1 Aim :
The aim of this experimental investigation is to study the flexural behavior of conventional concrete beams as well as self compacting concrete beams. In this investigation, a series of Nine numbers of under reinforced concrete Rectangular beams are tested to investigate the ultimate load carrying capacity and maximum deflections.
4.2 Testing of Materials :
4.2.1 Cement :
Ordinary Portland 53 grade cement of Birla Super brand confirming to IS : 12269-1987 from a single lot was used throughout the course of investigation.
4.2.2 Flyash :
Flyash depends on the chemical properties and the fineness of the Portland cement in the mix. Flyash obtained from Raichur Thermal Powder Plant, Karnataka with specific gravity of 2.3.
4.2.3 Silica Fume :
Silica fume is a by-product of silicon or Ferro-Silica industry and is 100 times finer than cement. The specific gravity of silica fumes is generally 2.20 but it is very slightly higher when the silica content is lower. This value can be compared with the specific gravity of Portland cement, which is 3.15 the particles of silica fume are extremely fine, most of them having a diameter ranging between 0.03 and 0.3m m; the median diameter is typically below 0.1m m. The specific surface of such fine particles cannot be determined using the Blaine method; nitrogen adsorption indicates a specific surface of about 20000 m2/kg, which is 13 to 20 times higher than the specific surface of other pozzolanic materials, determined by the same method. Such fine material as silica fume has a very low bulk density : 200 to 300kg/m3.
4.2.4 Fine Aggregate (F.A.) :
The aggregate which is passing through 4.75 mm sieve is known as fine aggregate. Locally available river sand which is free from organic impurities is used. Sand passing through 4.75mm sieve and retained on 150 micron IS sieve is used in this investigation.
4.2.5 Coarse Aggregate :
The coarse aggregate used in this investigation in 20mm down size crushed aggregate and angular in shape.
4.2.6 Water : (IS:456-2000)
Water used for both mixing and curing should be free from injurious amount of deleterious materials. Potable water is generally considered satisfactory for mixing and curing concrete. In the present work portable tap water was used.
4.2.7 Admixture : Fairflo :
Fairflo is a high performance superplasticizer intended for applications where increased early and ultimate compressive strengths are required, and it has been developed for use in Self compacting concrete and many more .
Fairflo is differentiated from conventional superplasticisers in that it is based on a unique carboxylic ether polymer with long lateral chains. This greatly improves cement dispersion. At the start of the mixing process an electrostatic dispersion occurs but the cement particle's capacity to separate and disperse. This mechanism considerably reduces the water demand in flow able concret.
Technical Support :
Fosroc provides a technical advisory service for on-site assistance and advice on mix design, admixture selection, evaluation trials and dispensing equipment.
Appearance : Light yellow coloured liquid
pH : 6.5
Volumetric mass @ 20Â°C : 1.06 kg / litre
Chloride content : Nil to IS : 456
Alkali content : Typically less than 1.5 g Na2O equivalent / litre of admixture
4.3 Concrete Mix designed for CVC :
Indian standard method of mix design (as per IS 456 - 2000, IS 10262 - 1982 and SP - 23) the mix design of plain concrete is
The mix proportion per cubic meter of concrete then becomes.
Water Cement Fine aggregate Coarse aggregate
191.6 lts 491.30 kg 516 kg 1181 kg
0.39 1 1.198 2.40
4.4 Mix Proportion :
SCC is largely affected by the characteristic of materials and mix proportions. Binu Sukumar et.al (12) have proposed a mix proportion for SCC from that mix proportion a ratio of coarse aggregate to fine aggregate have been taken i.e. CA / FA = 0.86.
A mix have been design for CVC of grade M30 grade then with above ratio and CVC mix proportion, a mix have been arrived for SCC.
Mix proportion of CVC
Mix proportion SSC
Mix M1 1 : 1.52 : 1.30
Mix M2 1 : 1.198 : 1.03
Mix M3 1 : 1 : 0.86
Table - 2: Mix, M3 equivalent to M30 grade
4.5 Workability test results :
Test carried out for fixing the dosage of superplasticizer for different grades.
Slump flow by Abrams cone
T50 cmslump flow
Table - 3: Test values
4.6 Cost Comparison :
A cost comparison of SCC is made with conventional concrete of the same strength. As regards of the cost of SCC, the increase in the cost of SCC on account of material is 10-12% only. If the savings in the cost of SCC could be on par or even lower than that of the corresponding conventional concrete. Bonus is the improved durability and strength.
4.7 Specimen Details :
The specimen are classified into two groups.
1. Control specimen are as follows -
a. Cubes of 150mm x 150mm x 150mm size
b. Cylinder of 100mm dia x 200 mm length
c. Prism of 100mm x 100mm x 500mm size
2. Test specimen are as follows -
CVC set of beam tested for conventional concrete of grade M30 of span 2300mm, effective span 2150mm, width 150mm, depth 230mm.
SSC set of beam tested for Mix M3 (Equivalent to M30 grade concrete) of span 2300mm, effective span 2150mm, width 150mm, depth 230mm.
4.8 Casting and curing of specimens :
4.8.1 Casting of control Specimens :
The moulds of size 150x150x150mm, 10mm dia x 200mm height and 100x100x500mm are used for casting of cubes, cylinders and prisms respectively. The moulds are cleaned and the corners are pasted with oil. One coat of cutting oil is applied on all the internal surfaces. The moulds are filled in three layers and the height of each layer is about 1/3rd height of mould, each layer is compacted by giving 25 blows with a tamping rod over the entire cross section uniformly for CVC members and no compaction is done for SCC members. After filling and compacting the mould, the top surface are made smooth and kept for a period of 24 hours.
4.8.2 Casting of Test Specimen :
Wooden moulds of internal dimensions 2300mm x 150mm x 230mm are used for casting the beams. The internal surfaces are cleaned and mould oil paste is applied at all corners, then a coat of cutting oil is applied on all internal surfaces. Steel reinforcement cage prepared earlier is kept in the mould. To obtain the required effective depth mortar blocks of 25mm thickness are kept one at each end. The mould is filled with the concrete in three layers, height of each layer being 1/3rd height of mould and compacted uniformly over the entire cross sectional area with tamping rods for CVC members and no compaction for SCC members.
4.8.3 Test for Compressive Strength (IS 516-1959) :
The compressive strength of concrete is one of the most important properties of concrete in most structural application concrete is implied primarily to resist compressive stress.
Graph No 01 Comparison and Effect of Curing on Compressive Strengths of SCC
(Mix M3 equivalent to M30 Grade) and CVC of M30 Grade
4.8.3Test for split Tensile Strength :
. These tests were carried out as per the specifications of IS : 58166 - 1970 (14) on three numbers of cylindrical specimens. The tensile strength of concrete was calculated by using the formula;
Number of cylinders tested for different proportion with cvc and scc are shown below
No. of Cylinders
Comp Load (Tons)
Split tensile strength
Average split tensile stre(N/mm2)
Table- 04 Split tensile strength of SCC-mix M3 (equivalent to M30)
4.8.4Test for Flexural Strength (IS516-1959) :
. The test is performed in accordance with IS 516-1959.
The maximum tensile stress readed is called modulus of rupture and is computed from the standard formulae.
F = M / Z
M = Bending moment at the section where rupture occurs
Z = section modulus
Z = I/Y
I = moment of inertia of the section
Y = distance from neutral axis = d/2
Number of prisms test for different proportions with CVC and SCC are shown in table number 11(A) - 11 (F).
No. of Cylinders
Crushing Load (Tons)
Flexural Strength (N/mm2)
Average Flexural strength (N/mm2)
Table No 5 Flexural strength of SCC For Mix M3
5. Testing and Results of SCC Beams
5.1 Testing Procedure :
After 28 days of curing, the beams were surface dried, they were cleaned with a wire brush to remove all grit and dirt. Then all the specimens were white washed from all the sides to facilitate easy detections of crack propagation. The beams are tested for pure flexure on a loading frame of 500 KN capacity, the beam is kept on two girders, so as to obtain the clear span of 2000 mm. On the beam, two rods are kept at a distance of 360mm from center of the beam on either side so that it acts as a two point loading, over which an I-section is placed. By sing a plumb, the centre line of the beam and the hydraulic jack were made to coincide with each other in order to prevent eccentric loading on the beam.
The test results of the beams tested are given in table number 12-15, graph number 4-7, showing load deflection curve.
5.2 Test Results of CVC & SCC beams :
Graph No 02 Load Vs Deflection Curves for SCC (Mix M3 equivalent to M30 Grade Beams)
Graph No 03 Load Vs Deflection Curves for SCC (Mix M3 equivalent to M30 Grade Beams)
6.1 Observations :
During the experimental work, close observations have been done to study the following.
It is noted that the load carrying capacity of SCC member is more compared to CVC member.
The crack width have also decreased for SCC members compared to CVC members.
the first crack appeared for CVC member at early stage, where as for SCC member the first crack has appeared later.
The present investigation has shown that it is possible to design a self compacting concrete incorporating class F fly ash & silica fame. The fly ash self compacting have a slump flow in the range of 600 to 800mm, a flow time (funnel) ranging from 8-10 seconds.
Strength development at the early ages is found to be similar to that of conventionally vibrated concrete.
In case of Mix M3 one day strength is found to be 13 MPa. This is nearly 25% of 28 day strength.
SCC is found to be a very good alternative for conventionally vibrated concrete.