EXPERIMENTAL STUDY ON ANCHORAGE BOND IN HIGH STRENGTH REINFORCED CONCRETE BEAMS

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International Journal of Civil Engineering and Technology (IJCIET)
Volume 8, Issue 1, January 2017, pp. 63–71, Article ID: IJCIET_08_01_007
Available online at http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=1
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication
EXPERIMENTAL STUDY ON ANCHORAGE BOND IN
HIGH STRENGTH REINFORCED CONCRETE BEAMS
Esraa Kamal Jaafar
Assistant Lecturer, Civil Engineering Department,
College of Engineering, Al-Mystansiriya University, Iraq
ABSTRACT
This paper discuses experimentally the effect of steel bar diameter and embedment length on
the bond stresses, bond stress versus slip relation, failure pattern and load versus deflection
response of high strength reinforced concrete beams with dimensions (100 mm width x200 mm
height x1100 length). Four beams specimens were provided with three embedment lengths (80
mm), (100 mm) and (120 mm) in addition to two different bar diameters (10mm) and (16mm). The
test results concluded that the bond stresses and the relative displacement decrease with increasing
the embedment length and bar diameter.
Key words: Bond Stress, slip, high strength concrete, embedded length, bar diameter.
Cite this Article: Esraa Kamal Jaafar, Experimental Study on Anchorage Bond in High Strength
Reinforced Concrete Beams. International Journal of Civil Engineering and Technology, 8(1),
2017, pp. 63–71.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=1
1. INTRODUCTION
Due to importance of bonding failure in concrete structures, several investigations have been developed to
enhance the bond strength between steel bar and concrete. Most of the studies that dealt with the effect of
development length on bond characteristics concluded that increasing the development length impact
positively on the bond characteristics (1-6)
.
The effect of bar diameter has been studied by [Mohammad N.S Hadi](7)
[Kazim Turk et.al](8)
,
[Soroushain P. and Choik. ](9)
and [Al-Aukaily A. F.], these investigations concluded that the bond strength
decreased with increasing bar diameter.
The increasing of concrete compressive strength have a beneficial effect in improving the bond
characteristics and this is what has already been proven by [A. Forough – Asl et.al](11)
, [Kafeel Ahmed ](12)
, [Khodaie and Nahmat](13)
and [ M. Veera Reddy](14)
.
In recent decades, studies on the bond characteristic between steel bars and new type of concrete has
emerged [Forough – Asl et.al](11)
and [M. Mazloom and K. Momeni](15)
studied the bond between
reinforcement bars and self-compacting concrete. They concluded that bonding strength was increased
when using self-compacting concrete in comparison with normal strength concrete.
Also, the bond between reinforcement bars and reactive powder concrete was studied by [Mahesh
Maroliya](16)
, [Deng Zong - Cai](17)
and [Lee M. et.al](18)
. The improvement of bond characteristics is clear
when using reactive powder concrete.

Esraa Kamal Jaafar
Figure 1 Experimental Detail of Tested Beams
2. EXPERIMENTED PROGRAM
The Experimented program of this study includes casting and examining four high strength reinforced
concrete beams with dimensions (100 mm width x 200 mm height x 1100 length) to study the effect of
development length and steel bar diameter on the bond characteristics between reinforcement steel and
concrete, in addition to three specimens of cube, cylinders and prisms to evaluate the compressive strength,
modulus of rupture and modulus of elasticity for concrete mix. The beams are tested under two points
loads with (210mm) distance between them. The section dimensions, steel bars distribution and testing set
up are shown in Figure (1) and Table (1).
Table 1 Experimental Details of Tested Beams
3. MATERIALS PROPERTIES
3.1. Cement
The physical and chemical properties of cement used in this work are listed in Table (2) and Table (3), the
obtained results confirm ASTM C-150(19)
standards. The cement was stored in a dry place to avoid the
exposure to moisture.
Table 2 Physical Properties of Cement
Property Results
Fineness using Blain air permeability apparatus (m2/kg) 386
Safety (soundness) using autoclave method (%) 0.013
Compressive strength for cement paste cube (70.7mm) at : (3days) in
(N/mm2) or (MPa)
21.6
Compressive strength for cement paste cube (70.7mm) at : (7days) in
(N/mm2) or (MPa)
25.6
Specimen
Conf.
Dimensions (mm) Flexural Reinforcement Shear
ReinforcementWidth Height Length Tension
Reinforcement
Compression
Reinforcement
B1 100 200 1100 2Ø10 2Ø10 Ø8@60mm
B2 100 200 1100 2Ø10 2Ø10 Ø8@60mm
B3 100 200 1100 2Ø10 2Ø10 Ø8@60mm
B4 100 200 1100 2Ø16 2Ø16 Ø8@60mm

Experimental Study on Anchorage Bond in High Strength Reinforced Concrete Beams
Table 3 Chemical Properties of Cement
Components Results
SiO2 19.93
Al2O3 5.42
Fe2O3 3.48
CaO 62.59
MgO 1.86
SO3 2.05
Insoluble Residue 1.19
Loss On Ignition 3.47
Tricalcium aluminates 8.34 (From X.Ray diffraction)
Lime Saturation Factor 0.81
3.2. Coarse Aggregate
The maximum size of coarse aggregate used in this study is (14 mm). Table (4) illustrates the grading of
coarse aggregate which is confirm the ASTM C33M(20)
limits.
Table 4 Grading of Coarse Aggregate
No. Sieve size (mm)
Present work of coarse
aggregate (% passing)
ASTM C33M(20)
(% Passing)
1 25 100 100
2 12.5 95.15 95-100
3 4.75 53.23 25-60
4 2.36 4.4 0-5
3.3. Fine Aggregate
Table (5) illustrates the grading of the fine aggregate with maximum size (4.75 mm), the test results
confirm the ASTM C33M (20)
limits.
Table 5 Grading of Fine Aggregate
3.4. Steel Reinforcement
Three sizes of bars were used in this study, ∅8 mm, 10 mm and 16 mm. The strength properties of these
bars are shown in Table (6), the test results confirm ASTM A615(21)
.
No. Sieve size (mm)
Present work of fine
aggregate (% passing)
ASTM C33M(20)
(% Passing)
1 9.5 100 100
2 4.75 96.33 95-100
3 2.36 89.22 80-100
4 1.18 63.19 50-85
5 0.6 55.23 25-60
6 0.3 27.29 5-30
7 0.15 9.48 0-10

Esraa Kamal Jaafar
Table 6 Steel Bars Properties
∆
(mm)
UltimateStrength(Fu)
(MPa)
Yield Strength (fy)
(MPa)
Diameter
(mm)
10.35914118mm
10.866349110mm
11.568850616mm
3.5. Super-Plasticizer
Gelinium 51 was used as a super plasticizer material, Table (7) illustrates the typical properties of
Gelinium 51.
Table 7 Specifications of Gelinium 51
No. Main action Concrete super plasticizer
1 Color Light brown
2 pH. Value 6.6
3 Form Viscous liquid
4 Chlorides Free of chlorides
5 Relative density 1.08 – 1.15 gm/cm3 @ 25°C
6 Viscosity 128 ± 30 cps @ 20°C
7 Transport Not classified as dangerous
8 Labeling No hazard label required
4. MECHANICAL PROPERTIES OF CONCRETE
The concrete compressive strength, modulus of elasticity and modulus of rupture test were performed
according to ASTM C39(22)
, ASTM C469(23)
and ASTM C78(24)
respectively. Table (8) includes the
mechanical properties of concrete.
Table 8 Mechanical Properties of Concrete
Beam Configuration Compressive Strength
(MPa)
Modulus of Elasticity
(MPa x103
)
Modulus of Rupture
(MPa)
B1 62.8 34.3 9.80
B2 61.25 34.8 8.86
B3 69.0 36.4 10.00
B4 67.5 35.4 9.92
5. RESULTS AND DISCUSSIONS
5.1. Failure Pattern and Load – Deflection Behavior
As mentioned in Figures (2), (3), (4) and (5), the beams are not affected significantly by load application at
the early stages of loading. The small deflections give an indication on high stiffness of tested beams. This
behavior extends until initiation of cracks at the middle third of the beams under points loads. This stage of
load – deflection curve is approximately linear called an elastic stage.
After that, the stiffness of beams start to decrease as a result of propagation of cracks, the values of
deflections readings are larger than previous stage until yielding of steel bars. This stage of load- deflection

curve is also approximately linear, the lack of bond between steel bars and concrete is more characterized
at this stage. So, it is a non-elastic stage.
The later stage can be called a failure stage, which the deflection reading increase rapidly more than
previous stages until failure by bond between steel bars and concrete, see Figures (6), (7), (8) and (9).
Figure 2 Load-deflection Curve of Beam (B1)
0
5
10
15
20
25
30
35
0 1 2 3 4 5
Load(KN(
Deflection (mm(
0
5
10
15
20
25
30
35
40
0 1 2 3 4 5 6
Load(KN(
Deflection (mm(
0
10
20
30
40
50
60
0 5 10 15
Load(KN(
Deflection (mm(

Esraa Kamal Jaafar
Figure 6 Failure Mode of Beam (B1)
0
10
20
30
40
50
60
0 2 4 6
Load(KN(
Deflection (mm(

5.2. Bond Stresses Characteristics
As indicted in Table (9), the bond stresses decreased from 13.78 MPa to 13.23 MPa and from 13.78 MPa
to 12.56 MPa when the development length was increased from 80 mm to 100 mm and from 80 mm to 120
mm respectively. The same trend can be seen when the diameter of embedded bars increased from 10 mm
to 16 mm, the bond stress was decreased from 12.56 MPa to 11.29 MPa. In two cases (increasing the
development length and diameter), the mentioned decrease in bond stresses is attributed to increase the
frictional area between the steel bar and concrete.
Table 9 Bond Stresses between Steel Bar and Concrete
5.3. Bond Stress – Slip Relationship
The relative slip between steel bar and concrete measured by using dial gauge with accuracy (0.002).
Figures (6) and (7) show a bond stress versus slip response in beams specimens with different bars
diameters and development lengths. The obtained results significantly show that the initial stage of each
curve has same slop which gives an indication that bond stress at this stage is negligible and the chemical
bonding between steel bars and concrete is sufficient to carry the applied stresses. This stage of bond
stress-slip curve is approximately linear called linear elastic stage and the stiffness is still appearing high.
With increasing the load, the stress in bar is increased with initiation relative displacement between
steel bar and concrete. The chemical bonding between steel bar and concrete start to disappear and the
interlocking between ribs and surrounding concrete becomes an important parameter in resisting the bond
stresses. The micro cracks start to develop at the contact between ribs and concrete. The crushing of
surrounding concrete around the ribs has obtained at the advanced stage of loading.
The relative displacement between steel bar and concrete start to increase until failure by pulling out
due to an increase the diameter of hole around the steel bar.
The using of large diameter of steel bar negatively affect the amount of relative displacement between
steel bar and concrete because the number of interlocking ribs with concrete are few compared with small
diameters one with constant development length. The effect of increasing the development length causes
an evident decrease in the amount of slip, this reduction is attributed to increase the frictional area which
decrease the bond stress between steel and concrete.
B4B3B2B1Specimens No.
16101010Diameter (mm)
12012010080Development Length (mm)
11.2912.5613.2313.78Bond Stress (MPa)

Esraa Kamal Jaafar
0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040
Slip (mm)
0
5
10
15
BondStress(Mpa)
Bar diameter (mm)
db=16
db=10
0.000 0.010 0.020 0.030
Slip (mm)
0
5
10
15
BondStress(MPa)
Development length (mm)
ld=12db
ld=10db
ld=8db
Figure 10 Bond Stress-slip Curves of different Figure 11 Bond Stress-slip Curves of different
Bar Diameters Development Lengths
6. CONCLUSIONS
The test results led to the following conclusions:
1 – Increasing embedment length has a significant effect on decreasing the bond stresses.
2 - Increasing bar diameter leads to a decrease in the bond stress.
3 – In the first stage of loading, the chemical bonding between steel bar and concrete is sufficient to carry
the applied stresses.
4 – Due to increasing the frictional contact area, the slip between steel bar and concrete decreased when
increasing the embedment length.
5 – The slip between steel bar and concrete decreased when increasing the bar diameter.
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