BY

Dharaneeswari.S.KPunithavalli.M

(3rd civil – PITS college Thanjavur)

INTRODUCTIONHIGH STRENGTH CONCRETE BY USING STEEL FIBERS.

CONCRETE

Concrete is characterized by brittle failure. It can be

overcome by the inclusion of a small amount of short

randomly distributed fibers (steel, glass, synthetic and

natural).

HIGH STRENGTH CONCRETE

High strength concrete the presence of more constituent ingredients than the

conventional concrete calls for an adequate proportioning of mixtures to satisfy

the specified performance characterstics . Addition of fibers, special admixtures,

composites and other new materials are available and being developed every day

to satisfy the required performance and functions of the challenging concrete to

give significant improvement in flexural strength, impact strength and fracture,

toughness of concrete with smaller improvements in compressive strength.

STEEL FIBER REINFORCED CONCRETE

Fiber reinforcement is mainly used in shocrete, but can also be used in normal

concrete. Fibre-reinforced normal concrete are mostly used for on-ground floors

and pavements, but can be considered for a wide range of construction parts

(beams, pillars, foundations etc) either alone or with hand-tied rebars.

SOME TYPES OF FIBER

METHODOLOGY

COLLECTIONs OF MATERIAL

1.Cement

2.Coarse aggregate

3.Fine aggregate

4.Steel fibre

1.Fineness (%) Not exceed 102.Specific Gravity 3.153.Finess modulus(%) 2.854.Initial setting time(min.) >305.Final setting time(min.) <600

Compressive Strength (N/mm2)

1. 3-days >272. 7-days >373. 28-days >53

Property of Cement

Property Coarse aggregate Fine

aggregate

1. Specific Gravity 2.775 2.67

2. Finess modulus 7.46 2.9

3. Water absorption 1.46 -

4. Moisture content nill nill

Steel fibres

The typical diameter lies in the range of 0.25-0.75 mm hook end steel fibres are being used in this project. Length of these fibres is 30 mm and the aspect ratio of 55. Density of steel fibre is 7900 kg/cum.

1. Cross Section : Straight , hook- end,

deformed

2. Diameter : 0.3-0.7mm ( max 1mm)

3. Length : 25 – 35mm

4. Density : 7900 kg/m3

5. Young‘s Modulus : 2.1 x 105 N/mm2

6. Resistance to Alkalis : Good

7. Resistance to Acids : Poor

8. Heat resistivity : Good

9. Tensile Strength : 500-2000 N/mm2

10. Specific Gravity : 7.90

11. Aspect Ratio : 45, 55, 65, 80

12. General Use : 10 kg/m3

13. Elongation : 5-35 %

GENERAL PROPERTY DESCRIPTION SFRC

PROPERTIES OF STEEL FIBRES USED

Fibre type : Hooked steel fibres

Fibre length : 50mm

Tensile strength : 1100 N/mm2

Young’s modulus : 2×105 MPa

Density : 7800 kg/m3

Aspect ratio : 67

Diameter : 0.75mm

CASTING OF THE CONCRETE

CURING OF THE CONCRETE

DISCUSSIONS OF TEST

The cube compressive strength obtained for steel fibre mixed in the proportion

of 2.5% and 5.0 % (by weight), was 64MPa. The percentage increase of

compressive strength is 1.57 and 1.79 for the specimens conventional, 2.5%

and 5% respectively.

Discussing about the column test results under axial load condition, the

column with proportion of steel fibres as 2.5 %, 5 %( 5%) has the highest load

carrying capacity of 78 KN. The percentage increase of ultimate load of the

column is 1.37, 5.04 and 7.17, for the specimens conventional, 2.5% and 5%

Initiation of the crack was arrested due to the addition of steel fibre.

COMPRESSION TEST OF THE CONCRETE CUBES

RESULTS AND DISCUSSION Compressive strength of cubes:

Compressive strength for 2.5% of steel fibre

Compressive strength for 5.0% of steel fiber

Ultimate Strength for 5.0% of steel fibre specimen

Comparison of Ultimate Strength of the Cubes

Flexural strength for conventional beam

Flexural strength for 5% steel fibre

TEST RESULTS

The results of this work, it can be concluded that the column containing the

mix proportion of steel fibre (5.0%) can greatly enhance the strength

compared with another proportion of steel fibre.

STRESS-STRAIN RELATION BETWEEN HPFRC & FRC

Flexural Strength: Flexural bending strength can be increased of up to 3

times more compared to conventional concrete.

Fatigue Resistance: Almost 1 1/2 times increase in fatigue strength.

Impact Resistance: Greater resistance to damage in

case of a heavy impact.

Permeability: The material is less porous.

Abrasion Resistance: More effective composition against abrasion and

spalling.

Shrinkage: Shrinkage cracks can be eliminated.

Corrosion: Corrosion may affect the material but it will be limited in certain

areas.

Properties of Concrete Improved by Steel Fibers

The mixing of the Hooked steel fibres in the cubes ands column of

two different percentage is improving the compressive strength of

the cubes. Steel fibre reinforced concrete column arrest the

initiation of the failure of the column and takes more load. The cube

and column containing proportion of steel fibre, 2.5% and 5.0%

carries more loads.

1) Increase in strength of mixed steel fibre reinforced concrete of

proportion 5 % of 50 mm sizes were,

2) 13.55 percent in cube compressive strength

3 )14.03 percent in ultimate load carrying capacity of column

CONCLUSION OF THE TEST

Advantages of SFRC:

Fast and perfect mixable fibers and High performance

and crack resistance

Optimize costs with lower fiber dosages

Steel fibres reinforced concrete against impact forces,

thereby improving the toughness characteristics of

hardened concrete.

Usage of SFRC in Indian Projects:

• KRCL-MSRDC Tunnels.• NafthaJakarihydro electric project.• KOLhydro electric project.• Bagliharhydro electric project.• Chamerahydro electric project.• Uri dam.• Sirsisilam project.• Tehri dam project.• Salalhydro electric project.• Ranganadihydro electric project.

Major SFRC structures all over the world

REFERENCES

1. Ezeldin A.S and Balaguru P.N,” Normal and High Strength

Fibre Reinforced Concrete under Compression”, Journal of

materials in Civil Engineering, Nov 1992, Vol.4, No 4, pp 415-

429.

2. Ganesan, N. and Murthy, J.V., “Strength and Behavior of

Confined Steel Fibre Reinforced Concrete Columns”, ACI

materials journal, 1990, vol.87, no.3, pp.221-227.

3. Hsu, L.S. and Hsu, C.T., “Stress-Strain Behaviour of Steel

Fibre High Strength Concrete under Compression”, ACI

Structurel Journal, 1994, Vol.91, No.4, pp.448-457

THANK YOU . . .

ANY QUESTIONS…