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STUDY ON INFLUENCE OF RIB CONFIGURATION ON BOND STRENGTH DEVELOPMENT BETWEEN STEEL AND CONCRETE
*First Author:Shoaib Bashir Wani
M.Tech Structural EngineeringB.S.Abdur Rahman University
**Second Author:E.S.Junaid Ahmed
M.Tech Structural EngineeringB.S.Abdur Rahman University
***Third Author & Guide:Dr. M.S.Haji Sheik Mohammed
Professor Civil EngineeringB.S.Abdur Rahman University
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OBJECTIVE OF THE STUDY
To conduct pull out test as per IS 2770-1967 (Methods of testing bond in reinforced concrete –part 1 pull out test ) to assess the bond strength development between concrete and steel rebar.
Pull-out test was conducted on:i. Mild steel barii. HYSD –parallel ribbed bariii. HYSD – diamond ribbed bar
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INTRODUCTION
The interaction at the interface between two materials is commonly known as bond.
Bond strength between rebar and concrete is essential for reliable performance of reinforced concrete structures. Bond strength development at the interface is mainly depends on surface configuration.
The conventional high yield strength deformed (HYSD) and thermo mechanically treated (TMT) bars mostly used in the construction sites nowadays offers high strength , superior bond at interface and high resistance against pull-out forces.
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Three factors define the bond strength: chemical adhesion,
friction resistance, and mechanical interlocking of bar deformation (ribs on bar) and surrounding concrete.
Experimental studies to access pull-out behaviour of rebar in concrete were carried out as per IS: 2770 (Part I) – 1967 (Reaffirmed 2007) (Indian Standard Methods of Testing Bond in Reinforced Concrete).
This investigation analysis the bond strength behaviour of ordinary MS rebar, HYSD parallel rib rebar, HYSD diamond rib rebar
HOW BOND IS FORMED???
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MATERIAL STUDY
The materials used in experimental study include:i. 53 grade OPCii. 2.36mm downgraded river sandiii. 20mm downgraded coarse aggregateiv. MS rebar of fy= 250 MPa, HYSD parallel rib rebar, HYSD
diamond rib rebar of fy= 500 MPa of size 16 mmØ
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CONSTITUENT PROPERTIES
Cement (53 grade OPC) Specific gravity – 3.12
Fine Aggregate (2.36 mm
downgraded)
Fineness modulus – 3.05
Specific gravity – 2.4
Water absorption – 5.75%
Confirming to zone - IIGrading conforming to IS 383-1970
Coarse Aggregate (20 mm
downgraded)
Specific gravity – 2.5
Water absorption – 0.25%Grading conforming to IS 2386-1963
TABLE 1: MATERIAL PROPERTIES
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TABLE 2: MIX PROPORTIONS FOR 1M3 OF M30 CONCRETE AS PER IS 10262:2009
Cement
(kg)
Fine Aggregate
(kg)
Coarse Aggregate
(kg)
Water
(litre)
438 588.74 1044.22 197
1 1.344 2.384 0.45
TABLE 3: CHEMICAL COMPOSITION TEST RESULTS
Characteristic Test MS rebar Results
(16mm Ø)
HYSD (Parallel ribs)
Results (16mm Ø)
HYSD (Diamond ribs)
Results (16mm Ø)
Carbon, (%) 0.284 0.203 0.222
Manganese, (%) 0.553 0.696 0.567
Silicon, (%) 0.157 0.208 0.104
Sulphur, (%) 0.028 0.024 0.024
Phosphorous, (%) 0.036 0.033 0.032
Chromium, (%) 0.190 0.092 0.186
Nickel, (%) 0.099 0.068 0.069
Molybdenum, (%) 0.017 0.013 0.016
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TABLE 4: TENSION TEST RESULTS
TYPE
PROPERTIES
YIELD
STRENGTH (MPa)
ULTIMATE
STRENGTH
(MPa)
% ELONGATION% REDUCTION
IN AREA
MILD STEEL 466.72 583.40 27.5 54.23
HYSD PARALLEL RIB498.36 622.96 22.5 55.45
HYSD DIAMOND RIB
547.77 684.72 26.25 54.90
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EXPERIMENTAL PROGRAM
Pull-out test was carried out on rebars as per IS 2770 (Part I) – 1967.
Investigation was done on Mild steel rebar, HYSD parallel ribs rebar, HYSD diamond ribs rebar of 16mm diameter.
Totally nine specimens were subjected to pull-out test. Universal testing machine of 1000kN capacity was used for carrying pull-out test.
Dial gauges were used to measure the slip at LE & FE. Dial gauge with a least count of 0.01 mm was used in LE & dial gauge with a least count of 0.001 mm was used in FE.
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Bonded Length (= 5Ø) & Unbonded Length 4-Legged Mild Steel Clamp
Used To Maintain Eccentricity of Rebar
Extended length from bottom face = 20mm
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Figure 2: Arrangement of Mould for Casting Pull-
out Specimen
Figure 1: Arrangement of Pull-out Test Specimen
in UTM
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TEST RESULTS AND DISCUSSION The test results were analysed as per procedure outlined in IS
2770-1967 by observing the load at 0.25mm loaded end (LE) slip, 0.025mm free end (FE) slip and ultimate failure load
Types of specimen
Load (kN)
Usable Bond Strength
(N/mm2)
Variation
(%)
0.025mm FE slip
0.25 mm LE slip
Mild steel specimen 1 25.83 27.25 6.77 H̲specimen 2 13.5 15.45 3.84 - 43.27
specimen 3 25 25 6.21 - 8.27HYSD
parallel ribs
specimen 1 14.50 11.50 3.60 - 46.82
specimen 2 17.5 6.25 4.35 - 35.74specimen 3 29.5 9.25 7.33 + 8.27
HYSD
diamond ribs
specimen 1 20.79 19.9 5.17 - 23.63specimen 2 22 2.79 5.47 -19.20
specimen 3 40 21.5 9.94 + 46.82
TABLE 5: OBSERVATION ON PULL-OUT TEST
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Table 6: Usable Bond Strength of Mild Steel, HYSD Parallel
and HYSD Diamond Bar (For Optimum Among 3 Categories) Type of Specimen Load (kN) Ultimate Load
(kN)
Usable Bond Strength
(N/mm2)
Variation in Usable Bond
Strength
(%) 0.025mm FE slip
0.25 mm LE slip
MS rebar (S3) 25 25 29 6.21 ̲H
HYSD parallel rib rebar (S3)
29.5 9.25 110.05 7.33 + 18.03
HYSD diamond rib rebar (S3)
40 21.5 108 9.94 +60.06
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Figure 3: Load vs Slip behaviour of Mild Steel Rebars
0 0.02 0.04 0.06 0.08 0.1 0.120
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10
15
20
25
30
35
40
Specimen 1(mm)Specimen 2(mm)Specimen 3(mm)
Slip at free end (mm)
Load
(KN
)
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0 1 2 3 4 5 6 70.00
10.00
20.00
30.00
40.00
50.00
60.00
Specimen 1 (mm)Specimen 2 (mm)Specimen 3 (mm)
Slip at loaded end(mm)
Load (
KN
)
0 0.01 0.02 0.03 0.04 0.05 0.060.00
10.00
20.00
30.00
40.00
50.00
60.00
Specimen 1(mm)Specimen 2(mm)Specimen 3(mm)
Slip at free end(mm)
Load (
KN
)
Figure 4: Load Vs Slip Behaviour of HYSD Parallel Rib Rebars
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Figure 5: Load Versus Slip Behaviour of HYSD Diamond Rib
Rebar
0 2 4 6 8 10 120
20
40
60
80
100
120
Specimen 1(mm)Specimen 2(mm)Specimen 3(mm)
Slip at loaded end(mm)
Load(K
N)
0 0.2 0.4 0.6 0.8 1 1.20
20
40
60
80
100
120
Specimen 1(mm)Specimen 2(mm)Specimen 3(mm)
Slip at free end(mm)
Load(K
N)
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1) Usable bond strength values of MS rebar is nearer to ultimate load value which means mild steel cannot withstand more load once the slip occurs.
2) Usable bond strength values of HYSD parallel ribs is higher than mild steel about 18.03 % with greater ultimate load. This is due to presence of parallel surface protrusions or surface lugs which provide better mechanical interlocking.
3) The value of ultimate load of HYSD diamond ribs is comparatively higher than MS and HYSD parallel ribs. Unlike HYSD parallel bars the HYSD diamond ribs have criss-cross rib pattern which ensures better mechanical interlocking.
4) Usable bond strength of HYSD diamond ribs is 60.06 % and 35.60 % greater than MS rebar and HYSD parallel rib configuration bars respectively.
CONCLUSIONS
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REFERENCES• Abrams Duff A.,”Test of Bond between steel and concrete”, bulletin no. 71, University of
Illinois.• Ahmed K. Siddiqi Z.A and Yousaf M., (2007),” Slippage of Steel in High and Normal
Strength Concrete”, Pakistan Journal Engineering and Applied Science, Vol. 1, PP.31-39.• ASTM A944-10, “Standard test Method for Comparing Bond Strength of Steel Reinforcing
Bars to Concrete Using Beam-End Specimens”.• IS 2770:1967 Part 1,”Methods of Testing Bond in Reinforced Concrete Pull-out Test”, Part
1.• IS 456-2000 Plain and reinforced concrete code of practice, Bureau of Indian standard.• Experimental and Analytical Studies of the Bond Behaviour of Deformed Bars in High
Strength Concrete. 4th International Symposium on the Utilization of High Strength/ High Performance Concrete, pp.1115-1124, v. 3, Paris. 1996b.
• Belaid.F, Arligue.G, Francois.R (2011),’Effect of Bars Properties on Bond Strength of Galvanized Reinforcement’, Journal of Materials in Civil Engineering,13,pp.454-458.
• Anil K. Kar (2011),” A Rebar Durable Concrete Construction”, The Master Builder, pp.224-236, July, 2011.
• Anil K. Kar and Haji Sheikh Mohammed, M.S., (2013), “Performance of Concrete Flexural Elements Reinforced with C-Bars”, The Master Builder, Vol. 14,No. 7.pp 194-200
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Thank You
