International Journal of Civil Engineering and Technology (IJCIET)
Volume 10, Issue 08, August 2019, pp. 61-72, Article ID: IJCIET_10_08_006
Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=10&IType=8
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication
Ahmed M. El-Kholy*
Lecturer of Structural Engineering, Faculty of Engineering, Fayoum University, Kiman Fares,
Fayoum, Egypt.
Mohamed M. Masaoud
MSc Student, Faculty of Engineering, Fayoum University, Kiman Fares, Fayoum, Egypt
Magdy A. Abd El-Aziz
Professor of Properties and Strength of Materials, Faculty of Engineering, Fayoum University,
Kiman Fares, Fayoum, Egypt
* Corresponding author, e-mail address: amk00@fayoum.edu.eg
ABSTRACT
Strengthening slender reinforced concrete (RC) columns is a challenge because their sensitivity to overall buckling and the combination of the bending and compressive stresses. This paper presents experimental study for strengthening twenty long RC columns using enhanced ferrocement jackets. The column specimens have slenderness ratio of 17.6 and two different cross-sections (square and rectangular).
The utilized expanded metal mesh layers have different weights, lengths and numbers for each jacket. The twenty strengthened specimens and four reference non-jacketed specimens were tested under concentric compression loading. The results demonstrated the effectiveness of the ferrocement jacket in improving the column capacity, increasing the stiffness, and reducing the lateral deformation. The significance of the jackets is more evident for long RC columns with larger crosssection area, and for jackets with larger volume fraction of metal mesh layers at the middle-third of the column height.
Key words : Slender RC column; ferrocement jacket; strengthening; expanded metal mesh
Cite this Article: Ahmed M. El-Kholy, Mohamed M. Masaoud, Magdy A. Abd El-
Aziz, Enhanced Ferrocement Jackets for Strengthening Long Reinforced Concrete
Column. International Journal of Civil Engineering and Technology , 10(8), 2019, pp.
61-72 . http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=8 http://www.iaeme.com/IJCIET/index.asp 61 editor@iaeme.com

Ahmed M. El-Kholy, Mohamed M. Masaoud and Magdy A. Abd El-Aziz
Reinforced concrete (RC) long columns are aesthetic and efficient structural members to transfer the structure loads to the foundation. Many of the wonderful RC buildings, halls, and special structures in the world would not be impressive enough without the slender columns.
The RC column is categorized as long if its slenderness ratio λ (the height divided by the width for rectangular columns and by the diameter for circular columns) exceeds 15 and 12 for rectangular and circular columns, respectively, according to the Egyptian code for design and construction of concrete structures [1]. The long columns are sensitive to overall buckling at high compression loads and therefore their capacity is governed by not only the compressive stress but also the bending stress unlike the short columns. This characteristic of the long columns has significant impact on the typical jacketing procedure that increases the column confinement in the transverse direction to improve the concrete core effectiveness in order to sustain higher compressive stress. The typical composites confinement jacket for RC columns was investigated through numerous researches unlike the limited researches for studying the strengthening of slender columns. Nevertheless, the researches for strengthening long RC columns emphasized important observations such as the strengthening effectiveness is reduced with the increase of slenderness ratio, strengthening effectiveness is reduced with the increase of eccentricity of loading (if any), and the confinement jacket is not useful enough for slender columns. These observations were highlighted by Tarkhan [2], Youcef et al. [3], Gaidosova and Bilcik [4], and Pan et al. [5]. The composites confinement jacket types of RC columns are ferrocement jacket [6-8] and Carbon Fiber-Reinforced Polymer CFRP jacket [8-10]. The most important merit of CFRP jacket is that it does not increase the cross section area of the column. Nevertheless, it is not popular in the developing countries because of its high cost. The construction procedure and the cost of ferrocement jacket are appropriate enough to the construction environment in the developing countries. The metal meshes, either expanded metal mesh (EMM) or welded wire mesh (WWM) that are used with the cement mortar to form the ferrocement, is available in the markets of these countries. These metal meshes could be used not only as external confinement but also used as internal confinement reinforcement (instead of or combined with ties) as proposed by Razvi and Saatccioglu [11] and El-Kholy et al. [12].
The significant researches for strengthening slender RC columns ( λ >15) are summarized in the following lines. Tarkhan [2] strengthened six rectangular column specimens ( λ =15.8) with ferrocement jackets comprising EMM with huge steel area (4.7 Kg/m
2
) and installed with different mesh orientations. The reference column specimen and the strengthened six specimens were tested under axial compression loading and recorded high increment in the ultimate load of the strengthened columns especially for those comprising EMM oriented in the vertical direction. Malhorta [13] strengthened six square columns specimens ( λ =3, 7 and15) with ferrocement jackets comprising one or two WWM layers. Three reference specimens and the six strengthened specimens were tested under axial compression loading.
Significant improvements in the ultimate load were recorded for the jacketed specimens. Pan et al. [5] confined six elliptical modified rectangular column specimens ( λ ranges from 4.5 to
17.5) with FRP wraps. The specimens were tested under concentric compression loading to distinguish between the behavior of the short and slender columns. It was concluded that the strengthening effectiveness is decreased with the increase of the slenderness ratio. Challenge full scale testing of eight rectangular column specimens with λ =27 was conducted by
Gajdosova and Bilcik [4]. The axially loaded specimens comprised two references and six specimens strengthened with CFRP. The results demonstrated that mounting the CFRP strips longitudinally is effective for strengthening slender RC columns unlike confinement in the transverse direction. Another challenge of testing six square column specimens (three http://www.iaeme.com/IJCIET/index.asp 62 editor@iaeme.com

Enhanced Ferrocement Jackets for Strengthening Long Reinforced Concrete Columns references and three confined with CFRP) with λ =16, 19 and 27 was conducted by Youcef et al. [3]. The specimens were tested under eccentric compression loading.
This paper presents enhanced ferrocement jackets for square and rectangular RC long columns with slenderness ratio of 17.6. The jackets comprise EMM layers with different weights, lengths, and numbers to investigate the optimum ferrocement jacket for slender square and rectangular RC columns.
Twenty-four RC long column specimens with height of 2200 mm and slenderness ratio λ of
17.6 were tested under concentric compression loading. The specimens were divided into two groups according to the cross-section shape. Group1 represents the square cross-section with dimensions 125×125 mm, whereas group2 specimens have rectangular cross-section with dimensions 125×190 mm. Every group comprises two (one pair) reference non-jacketed column specimens and ten (five pairs) jacketed column specimens. The experiment plan and the configurations of the column specimens are given in Table 1. Except the EMM testing, all materials and specimens testing was conducted in the concrete research and material properties laboratory at Fayoum University. EMM testing was conducted in the material properties laboratory of the American University at Cairo.
Table 1 The experimental plan and details of the RC specimens and ferrocement jackets
Reinforcement Ferrocement jacket (EMM layers and remarks) ties i
SE i SF1N i
SF1
1/3
N i SF1N-D i
SF1K i SF
1/3
K i RE i RF1N i
RF2N i
RF1
1/3
N i
RF1K i RF
1/3
K
----
Thin
----
1
----
0.30 non-jacketed (reference)
-----
Thin 1+1/3 0.60 (0.40) 1/3 layer at column center
Thin 1 0.30 spiral
Thick 1
Thick 1/3
0.64 ----
0.64 (0.21) 1/3 layer at column center
---- ---- ----
Thin 1 0.30 non-jacketed (reference)
-----
Thin 2 0.60 -----
Thin 1+1/3 0.60 (0.40) 1/3 layer at column center
Thick 1
Thick 1/3
0.64
0.64 (0.21)
----
1/3 layer at column center i =specimen repetition= 1, 2 x Ø y indicates x bars (or ties) of diameter y mm
/m indicates per longitudinal meter values in parentheses represent the average value on the total height
Portland cement type1 (CEM1) of grade 42.5N conforming Egyptian Standards (ES) 4756-
1/2013 [14] was used. Local basalt was used as coarse aggregate. The basalt was well graded with maximum size of 14 mm, specific gravity of 2.6, crushing strength of 20%, absorption percentage of 2%, Chlorides content of 0.018%, and Sulphates content of 0.21%. The used http://www.iaeme.com/IJCIET/index.asp 63 editor@iaeme.com

Ahmed M. El-Kholy, Mohamed M. Masaoud and Magdy A. Abd El-Aziz fine aggregate was natural siliceous sand with fineness modulus of 2.12, specific gravity of
2.5, bulk density of 1650 Kg/m3, percentage of clay and other fine materials of 1.1%, absorption percentage of 1.9%, Chlorides content of 0.04%, and Sulphates content of 0.31%.
Physical and chemical results of both coarse and fine aggregates conform ES 1109/2008 [15].
High grade (360/520 MPa) tensile steel and mild steel (grade 280/450 MPa) were used for longitudinal and transverse reinforcements, respectively. Tests conducted on the reinforcement steels show that they conform ES 262-1/2015 [16] and ES 262-2/2015 [17] for grades 280/450 and 360/520, respectively. For the utilized thin EMM, the dimensions of the diamond opening and the strand cross-section were 30×20 and 1.2×0.6 mm, respectively, whereas the corresponding dimensions of the used thick EMM were 32×16 and 1.5×0.9 mm, respectively. The thin and thick EMM types weighted 0.48 Kg and 1.00 Kg per square meter, respectively. The average specific gravity was 6.7 for the two types. Two strands were excluded from the thick EMM, and were tested under uniaxial tension. The results were shown in Figure 1. The average yield and ultimate stresses were 148 and 276 MPa. The concrete compressive strength was 25 MPa after 28 days for standard 150 mm cubes. The concrete-mix ratios were 350 kg/m
3
cement, 175 kg/m
3
tap water, 1222 kg/m
3
basalt, and 611
Kg/m
3
sand. Silica fume was used to produce high strength mortar for the ferrocement jacket.
The mortar compressive strength was 47 MPa after 28 days for standard 70 mm cubes. The mortar mix weight-ratios were 2, 0.5 and 0.1 for sand, water and silica fume, respectively, compared with the cement weight. The specifications of all used materials were consistent with provisions of the Egyptian code for design and construction of concrete structures (ECP
203/2018) [1].
Figure 1 Elongation of the EMM strand
The program comprises three phases to prepare, preload and strengthen the column specimens.
Table 1 shows that all the column specimens contain vertical reinforcement (grade 360/520) of four corner bars with 10 mm diameter. The rectangular columns have additional two middle bars. Also, all the specimens have typical transverse reinforcement (grade 280/450) of five square ties (8 mm diameter) per longitudinal meter. The volumetric ratio of the lateral reinforcement is equal to 0.61% compared with the concrete volume. The ends of the vertical bars were bent horizontally and two confining ties of 8 mm diameter were added at the end of each column specimen to secure the specimen ends similar to the configurations adopted by
El-kholy and Dahish [18]. http://www.iaeme.com/IJCIET/index.asp 64 editor@iaeme.com

Enhanced Ferrocement Jackets for Strengthening Long Reinforced Concrete Columns
Figure 2-a shows the wooden forms that were prepared to cast the specimens. The inner surfaces of the forms were overlaid by a release agent and then the steel reinforcement cages were aligned in the forms (Figure 2-b) with clear cover of 15 mm.
The components of the concrete (with the ratios given in section 3) were mixed using electrical mixer. The fresh concrete was poured into the specimens forms (Figure 2-c).
Electrical vibrator was used to consolidate the concrete. The sides of the forms were removed after 24 hours and the specimens were cured for 28 days using the wet burlap (Figures 2-d, 2e and 2-f).
The twenty-four column specimens were preloaded with concentric compression load equal to 60% of the ultimate load of the reference specimen in each group. Figure 2-g illustrates the preloading phase. The reason of the preloading phase is to simulate the practical field. It is worth mentioning that the twelve specimens of each group are identical in terms of the dimensions, reinforcement and preloading up to this second phase.
Electrical angle grinder with carbon disc was used to partially abrase the side surfaces for ten specimens of each group to increase their roughness to be ready for jacketing the specimens with interlocking between the original concrete and the ferrocement jacket. The remaining two specimens in each group (which are in their original form without grinding) will be labeled as reference specimens. The EMM layers of the ferrocement jackets were prepared according to the type, number and length specified in Table 1 for each pair of the five strengthened specimens pairs in each group. The EMM layer was wrapped around the roughened surfaces of the columns with adequate overlapping. Electric drill was used to install fasteners acting as shear connectors between the original concrete and the ferrocement jacket. Figure 2-h illustrates the EMM layers wrapped and connected around the roughened surface of the concrete specimens.
High strength cement mortar was prepared according to the ratios given in section 3.
Powerful adhesive (addibond 65 [19]) was used to produce adhesive slurry for bonding the fresh mortar to the original concrete. The mortar was added to the roughened specimen using trowel and adequate pressure to densfiy the mortar in the jacket as shown in Figure 2-i. The finish of the jacket surface was done using the trowel, lath and the spirit level to ensure the straightness and the horizontality of the surfaces as shown in Figure 2-j. The final crosssection of the RC specimens increased 20 mm from the four sides (Figure 2-j). After 24 hours, the twenty strengthened column specimens were cured using wet burlap (as shown in
Figure 2-k) for 28 days. http://www.iaeme.com/IJCIET/index.asp 65 editor@iaeme.com

Ahmed M. El-Kholy, Mohamed M. Masaoud and Magdy A. Abd El-Aziz
Figure 2 The process of preparing, preloading and strengthening the specimens http://www.iaeme.com/IJCIET/index.asp 66 editor@iaeme.com

Enhanced Ferrocement Jackets for Strengthening Long Reinforced Concrete Columns
(INSTRUMENTATION AND
TEST SETUP)
All the twenty-four specimens were loaded with axial compression (till failure) using 100 kN capacity loading frame as shown in Figure 3. Two rigid steel plates and clamps were used at the ends to distribute the load and confine the stressed loading ends of the column specimen.
Three displacement transducers were used to monitor the axial and the lateral deflection in two perpendicular directions at the column mid-height as illustrated in Figure 3. Two strain gages were used to monitor the lateral strain on the concrete surface at the mid-height.
Figure 3 Test setup
Table 2 shows the average results for the six pairs of each group. The ultimate load, axial displacement, lateral displacement and energy absorption are listed in Table 2 for every pair.
Also, their increment percentages compared with the reference pair are given in the table.
Figure 4 illustrates the load-axial displacement histories for the two tested groups. Figure 5 shows the percent increment in the ultimate load for jacket specimens compared with the non-jacketed specimens. Figure 6 illustrates the failure modes and the cracks for the tested specimens. Figures 7 and 8 show the percentage increment in axial displacement and percentage decrement in lateral displacement, respectively, for jacketed specimens compared with non-jacketed specimens. Similarly, Figure 9 shows the strain absorption results.
Figure 5 demonstrates that all jacketed specimens sustained higher load capacity (compared with the reference specimens) except SF1N-D due to the existence of large number of EMM overlaps in the spiral wrapping that interrupts the jacket continuity. Also, the result of SF1N-
D confirms the low effectiveness of the confinement jacket for slender columns. It could be argued that the higher cross-section area and the higher minor second moment of inertia of the rectangular columns (about 1.4 times those of the square specimens) increased the ultimate load improvement of the rectangular column specimens compared with the square specimens as evident from the comparison between Figures 5-b and 5-a. http://www.iaeme.com/IJCIET/index.asp 67 editor@iaeme.com

Ahmed M. El-Kholy, Mohamed M. Masaoud and Magdy A. Abd El-Aziz
Table 2 The results of strengthened column specimens compared with reference specimens
Group
1
2
Specimen
ID
Ultimate load kN ±% i SE 441.13 ---- i
SF1N 467.47 5.97 i
SF1
1/3
N 450.03 2.02 i SF1N-D 439.56 -0.36 i SF1K 573.38 29.98 i SF
1/3
K 568.15 28.79 i RE i
RF1N
514.81 ----
637.28 23.79 i RF2N 787.66 53.00 i RF1
1/3
N 627.7 21.93 i RF1K i RF
1/3
K
751.45
726.29
45.97
41.08
Axial displacement Lateral displacement Energy absorption mm ±% mm ±% kN.mm ±%
11.75
11.50
11.25
11.50
12.00
11.75
12.00
12.25
12.25
12.50
12.75
11.75
----
-2.13
-4.26
-2.13
2.13
0.00
----
2.08
2.08
4.17
6.25
-2.08
10.50
9.50
12.00
9.50
8.50
8.00
11.00
6.00
1.00
3.00
1.00
2.75
----
-9.52
14.29
-9.52
-19.05
-23.80
----
-45.45
-90.90
-72.70
-90.90
-75.00
2591
2687
2531
2527
3440
3337
3088
3903
4824
3923
4790
4266
±% indicates percentage of increment (+) or decrement (-) in value with respect to non-jacketed specimen
----
3.71
-2.32
-2.47
32.77
28.79
----
26.39
56.22
27.04
55.12
38.15
It is noticeable that the strength improvement is minor for square jacketed columns with thin EMM as shown in Figure 5-a. The two reasons behind this observation are the small cross-section of the square column specimens and the low volume fraction of the thin EMM.
For the square specimens jacketed with thick EMM and for all the rectangular column specimens strengthened with either thin or thick EMM, the improvement in the ultimate load was significant. The average improvements in the strength were 29%, 23% and 44% for the square specimens jacketed with thick EMM, rectangular specimens jacketed with thin EMM, and rectangular specimens jacketed with thick EMM, respectively. The capacity improvement for the thick EMM jacket is approximately twice that for thin EMM. It is worth mentioning that the volume fraction of thick EMM is also approximately twice that of the thin layer as Table 1 shows. The improvement percentages for thick layer and one-third thick layer jackets are close in each studied group. Therefore, one-third thick layer installed at the middle-third of the column specimen is more reliable (than complete layer) in terms of the cost and construction time. A glance to Figure 5-b shows that the two thin EMM layer jacket was slightly more efficient than the one thick EMM layer jacket although the volume fraction of two thin EMM layers is smaller than that of one thick layer. The reason behind this observation might be that the number of layers (not only the volume fraction) is an important parameter to improve the jacket efficiency. However, the ease of construction for the onethird thick EMM jacket still overrides the small additional gain of using two thin EMM layers.
The square jacketed column specimens with thin EMM layers and the reference non-jacketed specimens exhibited clear buckling at the mid-height of the column (level 1) as shown in
Figure 6. It is worth to remind that the improvement in the strength of these jacketed specimens as concluded and interpreted in section 6.1. The increase of the volume fraction reduces the deformation, and the failure still occurs in the middle-third of the column (level
2) but might be not in the exact mid-height. Also, using one-third EMM layer jacket reduces the deformation but moves the failure section out of the middle-third of the specimen. The failure occurs in the weak two-thirds height where only one EMM layer is installed. http://www.iaeme.com/IJCIET/index.asp 68 editor@iaeme.com

Enhanced Ferrocement Jackets for Strengthening Long Reinforced Concrete Columns
Figure 7 shows that the rectangular specimens exhibited insignificant increment in the axial displacement whereas the square specimens and those with one-third height thick EMM did not show any gain in the axial displacement.
Figure 4 Load–vertical displacement histories
Figure 5 Percent increment in ultimate load with respect to non-jacketed specimen
Figure 6 The failure modes and crack patterns of tested specimens
Figure 8-a shows that the reduction in lateral deformation was minor for the square specimens jacketed with thin EMM layer. For square specimens jacketed with thick EMM
(either whole or one-third layer), the reduction was significant (about 20%). On the other hand, Figure 8-b shows that the reduction in lateral deformation was evident and effective for all jacketed rectangular column specimens because of their original higher stiffness
(compared with square column specimens). Also, it is noticeable that the reduction in lateral http://www.iaeme.com/IJCIET/index.asp 69 editor@iaeme.com

Ahmed M. El-Kholy, Mohamed M. Masaoud and Magdy A. Abd El-Aziz displacement for the rectangular specimens jacketed with thick EMM layer (or two thin layers) was approximately double that of the specimens jacketed with one thin EMM layer.
Based on the preceding discussions of the displacement results, the improvement in ductility is insignificant for all specimens because there is no noticeable increase in the axial displacement. However, the improvement in the stiffness of the columns is noticeable in
Figure 4. The more ultimate load is sustained, the more improvement in the stiffness is. The stiffness improvement was higher for the specimens (square or rectangular) jacketed with two thin EMM layers or one thick EMM layer, and moderate for the rectangular specimens jacketed with thin EMM layer.
Figure 7 Percent increment in axial displacement with respect to non-jacketed specimen
Figure 8 Percent decrement in lateral displacement with respect to non-jacketed specimen
Figure 9 Percent increment in energy absorption with respect to non-jacketed specimen
Figure 9 shows the increment in the absorbed energy for the jacketed column specimens compared with reference specimens. The absorbed energy was calculated by estimating the area under the load-displacement curve. The area was approximated to triangle shape. Figure
4, Figure 7 and Table 2 show that all jacketed column specimens fail at close displacements http://www.iaeme.com/IJCIET/index.asp 70 editor@iaeme.com

Enhanced Ferrocement Jackets for Strengthening Long Reinforced Concrete Columns but different ultimate loads. Therefore, the ultimate load increment will govern that of the energy absorption. There was no increment in the energy absorption for the square column specimens jacketed with thin EMM layer. The increment became significant (average 29%) for square and rectangular column specimens jacketed with thick and thin EMM layer. The improvement in energy absorption was approximately doubled (average 50%) for rectangular specimens jacketed with two thin or one thick EMM layer.
Twenty RC long columns strengthened with ferrocement jackets and four non-jacketed reference specimens were tested under axial compression. All the twenty-four specimens are slender columns with 2200 mm height and slenderness ratio of 17.6. The ferrocement jackets comprise high strength cement mortar and EMM layers with different weights. The weight of the used thick mesh is approximately double that of the other used thin EMM. The EMM layers were used with the complete height of the columns or with only one-third height of the column specimens or wrapped spirally on the whole column specimen. The following conclusions are summarized.
1) The square column specimens sustained smaller ultimate load and exhibited more lateral deformation compared with the rectangular specimens (with the same width) because of their relative smaller cross-section area and moment of inertia.
2) The jackets of the square column specimens should comprise thick EMM with larger weight compared with rectangular column (with the same width) in order to obtain significant increment in the ultimate load and reduction of the lateral deformation.
3) The larger cross-section area of the column (and larger aspect ratio for the same width) increases the strengthening effectiveness (capacity and stiffness).
4) Spiral EMM ferrocement jacket is not effective for slender columns because it is explicit confinement jacket with no continuity (of EMM strands) in the vertical direction.
5) Increasing the surface weight of the EMM (volume fraction of EMM compared with the mortar volume) and also the number of layers increases the strengthening effectiveness (load capacity and stiffness).
6) The improvement in load capacity is proportional to the volume fraction of the used EMM layers.
7) The use of one-third height thick EMM layer at the center of the ferrocement jacket is considered as enhanced reliable jacket because of the low average volume fraction of the onethird height EMM (economic cost), ease of construction, and close effectiveness (capacity and stiffness) to the jackets with a complete height thick layer or two thin layers.
[1] Egyptian Code Committee: Egyptian code for design and construction of concrete structures (ECP 203-2017). Housing and Building National Research Center (HBRC),
Cairo (2018).
[2] Tarkhan, M.A.: Strengthening of loaded reinforced concrete columns using ferrocement jackets. IJIRSET. 4(12), 12154-12161 (2015).
[3] Youcef, S.Y.; Amziane, S.; Chemrouk, M.: CFRP confinement effectiveness on the behavior of reinforced concrete columns with respect to buckling instability. Constr.
Build. Mater. 81, 81–92 (2015). http://dx.doi.org/10.1016/j.conbuildmat.2015.02.006
[4] Gajdosova, K.; Bilcik, J.: Full-scale testing of CFRP-strengthened slender Reinforced concrete columns. J. Compos. Constr. (ASCE). 17, 239-248 (2013). http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000329
http://www.iaeme.com/IJCIET/index.asp 71 editor@iaeme.com

Ahmed M. El-Kholy, Mohamed M. Masaoud and Magdy A. Abd El-Aziz
[5] Pan, J.L.; Xu, T.; Hu, Z.J.: Experimental investigation of load carrying capacity of the slender reinforced concrete columns wrapped with FRP. Constr. Build. Mater. 21, 1991–
1996 (2007). https://doi.org/10.1016/j.conbuildmat.2006.05.050
[6] Kaish, A.B.M.A.; Jamil, M.; Raman, S.N.; Zain, M.F.M.; Alam, M.R.: An approach to improve conventional square ferrocement jacket for strengthening application of short square RC column. Mater Struct. 49, 1025–1037 (2016).
[7] Mourad, S.M.; Shannag, M.J.: Repair and strengthening of reinforced concrete square columns using ferrocement jackets. Cem. Concr. Compos. 34(2), 288-294 (2012).
[8] Yaqub, M.; Bailey, C.G.; Nedwell, P.; Khan, Q.U.Z.; Javed, I.: Strength and stiffness of post-heated columns repaired with ferrocement and fibre reinforced polymer jackets.
Compos Part B-Eng. 44(1), 200–211 (2013). https://doi.org/10.1016/j.compositesb.2012.05.041
[9] Chikh, N.; Benzaid, R.; Mesbah, H.: An experimental investigation of circular RC columns with various slenderness confined with CFRP sheets. Arab J Sci Eng. 37, 315-
323 (2012).
[10] Siddiqui, N.A.; Alsayed, S.H.; Al-Salloum, Y.A.; Iqbal, R.A.; Iqbal, R.A.; Abbas, H.:
Experimental investigation of slender circular RC columns strengthened with FRP composites. Constr. Build. Mater. http://dx.doi.org/10.1016/j.conbuildmat.2014.07.053
69, 323–334 (2014).
[11] Razvi, S.R.; Saatcioglu, M.: Confinement of reinforced concrete columns with welded wire fabric. ACI Struct J. 86(5), 615–623 (1989).
[12] El-Kholy, A.M.; Abd El-Mola, S.; Abd El-Aziz, M.A.; Shaheen, A.A.: Effectiveness of combined confinement with metal meshes and ties for preloaded and post-heated RC short columns. Arab J Sci Eng. 43, 1875–1891 (2018). https://doi.org/10.1007/s13369-017-
2782-x
[13] Malhotra, J.: Behavior of RCC columns confined with ferrocement. Master of Eng.
Thesis. Thapar University, Patiala, India (2013).
[14] Egyptian Standards-Building Materials Committee: Cement Part1: Composition, specifications and conformity criteria for common cements (ES 4756-1). Egyptian
Organization for Standards and Quality (EOS), Cairo (2013).
[15] Egyptian Standards-Building Materials Committee: Aggregates for concrete (ES 1109).
Egyptian Organization for Standards and Quality (EOS), Cairo (2008).
[16] Egyptian Standards-Ferrous Products Committee: Steel for the reinforcement of concrete
Part1: Plain bars (ES 262-1). Egyptian Organization for Standards and Quality (EOS),
Cairo (2015).
[17] Egyptian Standards-Ferrous Products Committee: Steel for the reinforcement of concrete
Part2: Ribbed bars (ES 262-2). Egyptian Organization for Standards and Quality (EOS),
Cairo (2015).
[18] El-Kholy, A.M.; Dahish, H.A.: Improved confinement of reinforced concrete columns.
Ain Shams Eng J. 7, 717-728 (2016). http://dx.doi.org/10.1016/j.asej.2015.06.002
[19] Chemicals for Modern Buildings CMB. Technical data sheet of powerful multi-use adhesive for mortar and concrete; Addibond 65. Cairo (Egypt): CMB; 2019. http://www.iaeme.com/IJCIET/index.asp 72 editor@iaeme.com