International Journal of Civil Engineering and Technology (IJCIET)
Volume 10, Issue 1, January 2019, pp.297–306, Article ID: IJCIET_10_01_028
Available online at http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=1
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
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EFFECT OF CONSTRUCTION JOINT ON
STRUCTURAL PERFORMANCE OF
REINFORCED SELF-COMPACTING
CONCRETE BEAMS
Murtada A. Ismael
University of Diyala, College of Engineering, Department of Civil Engineering, Iraq
Yahyia M. Hameed
University of Diyala, College of Engineering, Department of Architecture, Iraq
Haitham J. Abd
University of Baghdad, Department of Reconstruction and Projects, Iraq
ABSTRACT
This paper presents the effect of construction joints on the performance of
reinforced self-compacting concrete slender beams. The experimental program
included casting and testing four beams with dimensions of 125×150×1000 mm. The
first beam is without construction joint as a reference specimen, the second beam is of
horizontal construction joint at mid-depth of the beam, the third beam is of vertical
construction joint at mid-span (maximum bending moment point) and the fourth beam
is of vertical construction joint on fourth-span (maximum shear region). The test
results showed that the effect of construction joint on the ultimate load was more
significant than that on the first crack load, also, the results showed that the beam of
horizontal construction joint gave better structural performance as compared with the
other cases of the construction joint, in which the first crack load decreased 6.7% and
the ultimate load decreased 26.7%as compared with the reference beam. Also the
results showed that the beam with vertical construction joint on the fourth-span
represented the less efficiency case, in which the first crack load decreased 16.7% and
ultimate load decreased 56.2% as compared with the reference beam. Furthermore
the load-deflection becomes less stiff with presence construction joint especially
beyond the first crack load.
Key words: Beams, Structural performance, Construction joint, self-compacting
concrete.
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Cite this Article: Murtada A. Ismael, Yahyia M. Hameed and Haitham J. Abd, Effect
of Construction Joint On Structural Performance of Reinforced Self-Compacting
Concrete Beams, International Journal of Civil Engineering and Technology (IJCIET),
10 (1), 2019, pp. 297–306.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=1
1. INTRODUCTION
Construction joints are define as the places of stopping in the process of concrete casting in
the buildings and the structures and they are practically required when it is not possible to
complete the process of casting in one continuous operation due to many reasons related by
the amount of concrete that can be placed at one time which is governed by batching and
mixing capacity, crew size, and the amount of time available. Correctly located and properly
executed construction joints provide limits for successive concrete placements, without
adversely affecting the structure [1].On the other hand, in recent years, self-compacting
concrete (SCC) has been became an excellent alternative to conventional concrete in many
fields due to its special properties such as its ability to flow and fill the formwork under its
own weight without the need to use external vibrators, easy placement of concrete in
restricted sections and congested reinforcement areas without segregation, reduction in site
manpower and faster construction [2]. At the same time, As compared with conventional
concrete, SCC consists of lesser amount and smaller maximum size of coarse aggregate,
therefore, it is expected that the structural performance of SCC beams is different from that of
CC beams, where the interlock mechanism of coarse aggregate is weaker which is the
important factor in shear transfer and redistribution the internal stress in the concrete beams.
Most of the previous contributions which studied the effect of construction joint focused
on its impact on the mechanical properties of conventional concrete such as studying the
effect of construction joints on the shear strength of unreinforced concrete prisms which
presented by Clark and Gill [3], studying the effect of construction joints on the modulus of
rupture which presented by Issa et al [4],studying the effect of construction joint on splitting
tensile strength of concrete which is presented by Gergeset al [5], Rathi and, Kolase [6]
studied the effect on the strength of concrete, while the behavior of beams made of
conventional concrete presented by Jabir et al [7] and Abass [8].
All the previous studies did not study the effect of construction joint on self-compacting
concrete reinforced beams, therefore this research investigate the effect of construction joints
on the performance of reinforced self-compacting concrete beams.
2. EXPERIMENTAL PROGRAM
The experimental program consists of casting and testing four reinforced concrete slender
beams. The first beam is without construction joint as a reference specimen, the second beam
is of horizontal construction joint at mid-depth of the beam, the third beam is of vertical
construction joint at mid-span (maximum bending moment point) and the fourth beam is of
vertical construction joint on fourth-span (maximum shear region).All the beams made of
self-compacting concrete of about 32MPa compressive strength, and have the same
dimensions (1000mm length, 120mm width and 150mm height). Figure (1) shows the layout
and cross sections of these beams and Table (1) lists the details of type and location of
construction joint of each beam.
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Effect of Construction Joint On Structural Performance of Reinforced Self-Compacting Concrete
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Figure (1) Layout and cross-sections of the beams
Table (1) Type and location of construction joint of each beam
Beam designation
Type and location of construction joint
B1
B2
B3
B4
Without construction joint (reference )
Horizontal at mid depth
Vertical at mid-span
Vertical at fourth-span
3. CONSTITUENT MATERIALS
3.1. Self-compacting concrete
The ingredients of SCC used in this research include: Ordinary Portland cement Type I
conform to the requirements of the Iraqi specification No.5/1984 [9], crashed gravel as coarse
aggregate of maximum size 14 mm conform to the requirements of the Iraqi specification
No.45/1984 [10], Natural sand conform to the requirements of the Iraqi specification
No.45/1984 [10], Lime stone powder with particle size of less than 0.125 mm (Sieve No.200)
satisfies EFNARC 2002 recommendations [2], high range water reducers (S.P.) complies with
ASTM C494 type A[11] and tap water. The components of SCC used in this research and it
proportions per cubic meter are listed in Table (2).
Table 2 Quantities of SCC ingredients per cubic meter
Cement
(kg)
Limestone
powder (kg)
Water
(liter)
Sand
(kg)
Gravel
(kg)
400
134
192
821
767
Super plasticizer
(liter)
2.2
3.2. Steel reinforcement
All the beams are longitudinally reinforced by two deformed bars of 12mm diameter of 482
MPa yield stress as flexural reinforcement, 6mm@50mmof 392MPa yield stressas shear
reinforcement (stirrup), also to fix the stirrups 4mm smooth bars were used at top of beam.
The test results of the bars (ϕ12mm) and (ϕ6mm) satisfy ASTM A615 requirements [12].
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4. MIXING
The concrete mixing for SSC achieved using a titling horizontal rotary mixer machine. The
procedure of SCC mixing was as follows: firstly, the fine aggregate, cement and limestone
powder were mixed for one minute before adding half of the mixing water. Then, the mixture
was mixed for two minutes. The coarse aggregate was added and then the remaining quantity
of water with superplasticizer. Mixing was continued for two minutes to achieve uniform
distribution through the concrete mix.
5. FRESH SCC TESTS
In order to verify from being the concrete of the mixes is SCC, the four standard tests (Slump
flow test, T50 cm slump flow test, V-funnel test, and L-box fresh test) of SCC were carried
out on each batch and the results were compared with the standard limitations mentioned in
EFNARC [2]. Table (3) shows the results of these tests. It can be noted that the results of
these tests satisfy the requirements of EFNARC [2]. Figure (2) shows the photographs of
these tests.
Table (3) Results of fresh SCC for slump flow, T50, V-funnel and L-box tests
Mix name
SCC
Limits of EFNARC [2]
Slump flow
(mm)
680
650-800
T50
(sec)
4
2-5
V-funnel
(sec)
10
6-12
L-box
(H2/H1)
0.88
0.8-1
Figure (2) V-funnel, slump flow and L-box tests of fresh concrete
6. CASTING AND CURING
After mixing, the fresh SCC poured in timber molds of the beams. For the beam without
construction joint (reference specimen) the casting process was achieved in one stage, while
for the beams of construction joint, the casting process was achieved in two stages, in the first
stage a part of beam was casted and in the next day, the remaining part of beam has been
completed to construct the construction joint. Figure (3) shows the stages of the beam casting.
After 24 hours from the completion of the casting process of all stages, the beam specimens
were de-moulded, and immersions in a tank of water for 28 day according to ASTM C 192/C
192M-02 [13].
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Figure (3) beams casting stages (a) beam of vertical construction joint at mid-span (b)
reference and horizontal construction joint at mid-depth of the beam (c) beam is of
vertical construction joint on fourth-span
7. COMPRESSIVE STRENGTH OF HARDENED SCC
For each batch of SCC, cylinders of 150×300mm and prisms of (100×100×500mm) were
casted with the beams to determine the mechanical properties of SCC. The compressive
strength (fc') tests were carried out according to ASTM C39 [14]. Flexural strength (fr)
(modulus of rupture) tests were carried out according to ASTM C78 [15], while the indirect
tensile strength (fct) (splitting tensile strength) tests were carried according to ASTM C496
[16]. Table (4) lists the mechanical properties of SCC of each part of the beams.
Table (4) Mechanical properties of SCC of each part of the beams
Beam
B1
B2
B3
B4
Part
Full
Lower layer
Upper layer
First part
Second part
First part
Second part
f'c
32.2
32.2
32.8
32.2
32.8
32.2
32.8
fr
4.2
4.2
4.3
4.2
4.3
4.2
4.3
fct
3.8
3.8
3.9
3.8
3.9
3.8
3.9
8. TEST SETUP
The beams were lifted from the curing water tank at the age of 28 days after casting, left to
dry, and then painted with white colour so that cracks can be easily detected. The beams were
tested under two points loading using a universal hydraulic machine of 2000kN capacityas
shown in Figure (4). The beam specimens were tested as simply supported using rigid
supports with 900mm clear span and loading distance of 315mm from the support, in order to
provide a shear span to effective depth ratio equal to 2.5. The loads were applied in successive
increments up to failure. A dial gauge of 0.001 mm accuracy was attached firmly at the center
of the bottom face of the beam to record midspan deflection. The load that produced the first
crack and the ultimate strength were recorded. Crack patterns were marked on the beams.
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Figure (4) Testing setup
9. RESULTS AND DISCUSSION
9. 1. Failure modes and crack patterns
Figures (5) to (8) show the crack patterns at the failure for the tested beams. For the beam
B1which is a reference specimen (without construction joint), the first crack initiated from the
bottom of the beam in the mid-span where the maximum bending moment occurred, just the
tensile stresses exceeded the concrete rupture modulus. As the applied loading increased, the
first cracks widened and propagated vertically upward. Moreover, other flexural cracks also
developed and separated along the beams’ length. Diagonal cracks were noticed in the shear
zone, some of these cracks connected with the flexural cracking resulting in shear-flexural
cracks; finally, failure occurredas some of the shear-flexural cracks expanded and extended
deeply in the compressive zone towards the point load
The beam B2 of horizontal construction joint showed similar behavior to that of beam B1
in early stages of loading but as the flexural cracks reached the down level of the upper layer,
some of flexural crack continue to extend in the upper layer and some of new flexural cracks
formed in the upper layer and before the failure, sliding between the two layers occurred in
the shear zone resulting in failure.
Beam B3 which has a vertical construction joint at mid span also exhibited similar
behavior of beam B1, but just before the failure, the construction joint begun to expand
resulting in early failure as compared with B1.
The initial cracks of beam B4 which has vertical construction joint at the fourth span also
begun in the mid span of the tension region but as soon as the cracks extended to shear zone
under increasing loads, main crack formed in the construction joint leading to very early
failure as compared with the others beams.
Figure (5) Crack Patterns at failure of beam B1
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Figure (6) Crack Patterns at failure of beam B2
Figure (7) Crack Patterns at failure of beam B3
Figure (8) Crack Patterns at failure of beam B4
9.2. First crack load and ultimate load
Table (5) shows the first crack and ultimate load of the tested. Generally, it can be noted that
the effect of construction joint on the ultimate load is more significant than that on the first
crack load, and the beam with horizontal construction joint gave better performance in terms
of first crack load and ultimate strength as compared with the others beams, also, the beam
with vertical construction joint on the fourth span represented the less efficiency case in terms
of first crack and ultimate strength.
Table (5) Results of the tested beams
Beam
B1
B2
B3
B4
Type and
location of
construction
joint
Reference
(without)
Horizontal at
mid depth
Vertical at mid
span
Vertical at
fourth span
First
crack
load
(kN)
Decreasing
percentage
(%)*
Ultimate
load (kN)
Decreasing
percentage*
(%)
Ultimate
deflection
(mm)
Decreasing
percentage
(%)*
30
-
124.8
-
8.4
-
28
6.7
91.5
26.7
7.6
9.5
20
33.4
77.4
38.0
7.2
14.3
25
16.7
54.7
56.2
4.9
41.7
* As compared with B1
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However, presence horizontal construction joint in the mid depth of the beam B2 led to
decrease the first crack load 6.7% and the ultimate load 26.7%as compared with that of the
reference beam (B1). Also, the test results showed that presence vertical construction joint on
the mid span of the beam made the first crack load decrease with percentage of 33.4%, while
the decrease in ultimate load was 38% as compared with the reference beam (B1).
Furthermore, presence vertical construction joint on the fourth of span of the beam (B4)
reduced the first crack load of about 16.7% and ultimate load of about 56.2% as compared
with reference beam (B1).
Figure (9) shows load-deflection of the tested beams, it can be noted that generally
presence of construction joint in the beam made the beam less stiffer after first crack load as
compared with the beam without construction joint and before the first crack the effect is very
little. Also, Table (5) shows that presence horizontal construction joint in the mid depth of the
beam (B2) reduced the ultimate deflection of about 9.5%, while presence vertical construction
joint on the mid span of the beam made the ultimate deflection decrease with percentage of
14.3% and presence vertical construction joint on the third of span of the beam (B4) reduced
the ultimate load of about 41.7% as compared with reference beam (B1).
Figure (9) Load-deflection curves of the tested beams
The structural behavior efficiency of the beam of the horizontal construction joint (B2)
can be attributed to that presence of shear reinforcement provide a good bond between the
upper and lower layers and to some extent resisted the sliding or separation between the two
layers, this lead to good resistance against the loading but at higher loads no longer resist the
horizontal shear, thereforesliding occurred in the shear areas and accelerated the failure
compared to the reference beam.
On the other hand, for the beam of the vertical construction joint in the mid-span (B3), the
position of the construction joint is in the region of maximum bending moment and zero
shear. Thus, the presence of the construction joint does not pose any effect on the shear
resistance. Also, the bending moment will cause compression stress at the top of the beam
cross-section and tension stress on the bottom beam cross-section. Presence the construction
joint does not affect on theresistance of the beamagainst compression stress, and the tension
stress on the bottom of the beam cross-section resists by flexural reinforcement to a some
extent, but after the occurrence the first crack and as a result of higher loads, the construction
joint form a weakness region that lead to failure.
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For the beam with vertical construction joint on the fourth-span (B4) which represented
the less efficiency case, the position of the construction joint represents the area of the highest
shear stress and about half the maximum bending moment, so the shear stress is the risk in
this case. After spreading the cracks to the shear zone, the construction joint caused an early
weakness in the shear strength of the beam. The presence of shear reinforcement does not
improve this weakness as the construction joint is located between the stirrups resulting in an
early failure compared to the other cases.
10. CONCLUSIONS
Based on the results of the experimental work of this study, it can be concluded that:

The effect of construction joint on the ultimate load was more significant than that on the first
crack load.

The beam of horizontal construction joint gave better performance in terms of first crack load,
ultimate strength and load-deflection relationship. However, the first crack load decreased of
about 6.7% as compared with that of the reference beam, while the ultimate load decreased of
about 26.7%.

Presence vertical construction joint on the mid span of the beam made the first crack load
decrease with percentage of 33.4%, while the reduction in ultimate load was 37.9% as
compared with the reference beam.

Presence vertical construction joint on the fourth span represented the less efficiency case
comparing with the other beams of construction joint .However, the first crack load decreased
with percentage 16.7% and ultimate load decreased with percentage 56.2% as compared with
reference beam.

Generally, presence construction joint in the beam made the beam less stiffer after first crack
load as compared with the beam without construction joint and before the first crack the effect
is very little.

Presence horizontal construction joint in the mid depth of the beam reduced the ultimate
deflection of about 9.5% as compared with the reference beam, while presence vertical
construction joint on the mid span of the beam made the ultimate deflection decrease with
percentage of 14.3% and presence vertical construction joint on the third of span of the beam
reduced the ultimate load of about 41.7%.
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