Effect of Using Ferro-Cement on the Mechanical Properties of ...

13 th International Conference on
AEROSPACE SCIENCES & AVIATION TECHNOLOGY,
ASAT- 13, May 26 – 28, 2009, E-Mail: asat@mtc.edu.eg
Military Technical College, Kobry Elkobbah, Cairo, Egypt
Tel : +(202) 24025292 – 24036138, Fax: +(202) 22621908
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Paper: ASAT-13-MS-24
<strong>Effect</strong> <strong>of</strong> <strong>Using</strong> <strong>Ferro</strong>-<strong>Cement</strong> on the Mechanical Properties <strong>of</strong>
Reinforced Concrete Slabs Subjected to Dynamic Loads
Essam Eltehawy *
Abstract: This paper presents an experimental investigation performed on reinforced concrete
slabs, where plain cement mortar reinforced with welded steel mesh, known as <strong>Ferro</strong> cement
is applied.
The aim <strong>of</strong> this study is to observe the influence <strong>of</strong> using <strong>Ferro</strong>cement in enhancement the
mechanical properties <strong>of</strong> reinforced concrete slabs subjected to impact, penetration and fire.
The paper provides comparison between the performance <strong>of</strong> using the new technique, as a
strengthening material <strong>of</strong> reinforced concrete slabs and the existing reinforced concrete slabs.
The testing program included impact load testing, projectile impact test using projectile with a
diameter <strong>of</strong> 12.5 mm and subjecting the slabs to high flames <strong>of</strong> fire reaching 700 C o degrees
for 30 minutes.
The main findings showed that the use <strong>of</strong> the <strong>Ferro</strong>cement as a reinforcement to concrete
slabs enhanced the perforation resistance and reduce the heat transfer through the thinner
thickness <strong>of</strong> the steel mesh reinforced cement matrix.
1. Introduction
For structures protection, reinforced concrete is commonly used. However, concrete structures
subjected to dynamic loads due to explosion will respond differently than statically loaded
structure and the structure now is subjected to a combination <strong>of</strong> blast and fragments loads.
During blast and fragment impacts form small charges, the structure will shake, vibrate,
severe crushing <strong>of</strong> concrete occurs and crater forms in the front <strong>of</strong> the concrete. On the other
hand, if a large charge is used, large penetration will occur and will result in scabbing to the
back side <strong>of</strong> the wall or perforation with risk <strong>of</strong> injury for people inside the structure [1-5].
Thus, the strengthening <strong>of</strong> reinforced concrete slabs using ferrocement layers attached onto
the surface <strong>of</strong> the slabs are utilized in this paper to enhance the slabs resistance due to
different cases <strong>of</strong> dynamic loads [6]. Generally, ferrocement is considered as composite
material and it consists <strong>of</strong> cement mortar reinforced with layers <strong>of</strong> wire mesh with small
openings diameter [7]. Figure (1) illustrates different shapes <strong>of</strong> wire meshes that can be used
in ferrocement reinforcement. The early use <strong>of</strong> the ferrocement was mainly for repairing
purposes due to its flexibility to fit onto any surface. However, the use <strong>of</strong> ferrocement
expanded steel mesh reinforcement to be used as a strengthening material. There are many
advantages for the use <strong>of</strong> ferrocement that include toughness, crack resistance, ease <strong>of</strong>
application as well as its cheap price [8].
* Egyptian Armed Forces, Egypt

Paper: ASAT-13-MS-24
This paper mainly focuses on reducing the effect <strong>of</strong> direct weapons on the concrete structures.
Generally speaking, weapon systems can be divided into conventional weapons, nuclear
weapons, biological weapons and chemical weapons. The main concern <strong>of</strong> this paper is to
study the effect <strong>of</strong> conventional weapons attacks on reinforced concrete structure especially
those generating both blast waves and fragments [9]. The conventional weapons are divided
into direct and indirect projectiles. The damage <strong>of</strong> direct projectile without explosive is
caused by the mass and velocity <strong>of</strong> the projectile. For direct projectiles with explosive such as
grenades, bombs, torpedoes, missiles, and reboots, the damage is caused not only by the
primary kinetic energy for the projectile but also by the shock wave due to the explosion.
Furthermore, fragments are produced from the projectile case, which will fly towards the
target.
This paper is utilizing the technique <strong>of</strong> using ferrocement as a strengthening and repair
materials for existing reinforced concrete slabs [10], which depends on experimental
measurement <strong>of</strong> the depth <strong>of</strong> penetration. The depth <strong>of</strong> penetration is a function <strong>of</strong> the velocity
and mass <strong>of</strong> the projectile as well as the stiffness <strong>of</strong> the targets material. For concrete the latter
parameter is normally related to the compressive strength [11-14]. Finally, the objective <strong>of</strong>
this paper is to determine the effect <strong>of</strong> using different numbers <strong>of</strong> layers <strong>of</strong> ferrocement on the
behavior <strong>of</strong> reinforced concrete slabs subjected to dynamic loads that generates a combination
<strong>of</strong> blast wave and fragment impacts.
Fig. (1) Different types <strong>of</strong> wire meshes used in ferrocement reinforcement.
2. Experimental Program
The experimental program is divided into different stages
Specimens' Preparation
<strong>Ferro</strong>cement slabs Tests
Impact Penetration
Fire Fire & Penetration
2.1. Materials
The concrete was designed according to the American concrete institute (ACI) method to give
an average strength <strong>of</strong> 33.5 MPa after 28 days. Water/cement ratio was constant (W/C =
0.45). <strong>Cement</strong>, used was ordinary Portland cement with a density <strong>of</strong> 3150 kg/m
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3 and its
nominal content was 400 kg/m 3 . Fine aggregate was siliceous sand with a specific gravity <strong>of</strong>

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Paper: ASAT-13-MS-24
2650 kg/m 3 . Coarse aggregate was crushed dolomite stone <strong>of</strong> specific gravity 2550 kg/m 3 and
with maximum particle size 6.3 mm, the mix proportions by weight for 1 m 3 <strong>of</strong> concrete are
shown in Table (1).
Table (1) Mix proportions <strong>of</strong> concrete.
Material <strong>Cement</strong>
(kg)
Sand
(kg)
Crushed dolomite
(kg)
Water
(kg)
Kg/m 3 400 918 918 180
2.2. Specimen
Two classes <strong>of</strong> target specimens were considered, first control slab specimens and the other
was <strong>Ferro</strong>cement slab specimens, all specimens are square shaped with dimensions 55 x 55
centimeter and the depth is different according to the number <strong>of</strong> layers.
2.2.1. Control Specimens
The control slabs were mortar cement reinforced with hot rolled steel bars <strong>of</strong> diameter 10 mm
in two perpendicular directions with spacing <strong>of</strong> 15 cm between the bars, and the total depth <strong>of</strong>
the slabs was 10 cm &14 cm, Fig. (2).
2.2.2. <strong>Ferro</strong>cement Specimens
<strong>Ferro</strong>cement slabs were mortar cement reinforced with different numbers <strong>of</strong> expanded metal
sheet (style ½”- #16 from (LOUCON METAL LTD.), Fig. (3).
Fig. (2) Control specimens' preparation.

2.3. Tests Procedures
Fig. (3) <strong>Ferro</strong>cement technique specimens' preparation.
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Paper: ASAT-13-MS-24
2.3.1. Impact Test
The following Table (2) presents the slabs that have been tested under impact load. The
following slabs were tested at Carleton University civil laboratory to measure the penetration
depth under drop impact load. The slabs were installed on the test facility and they were tested
by using a weight to stroke the slabs. The weight was dropped under its own weight which
was 335.5kg. Figure (4) Shows the impact test.
Table (2) Slabs to be tested under drop impact load.
Slab Dimension(cm) Reinforcement Concrete dim. <strong>Ferro</strong>cement
SI-1 55×55×10 4�10 D 55×55×10 ---------------
SI-2 55×55×14 4�10 D 55×55×14 ---------------
SI-3 55×55×14 4�10 D 55×55×10 2 layers U,D*
SI-4 55×55×14 4�10 D 55×55×10 2 layers U,D**
D = Down layer, U = Upper layer
* 2 layers <strong>of</strong> ferrocement each layer contains 2 meshes
** 2 layers <strong>of</strong> ferrocement each layer contains 4 meshes
2.3.2. Penetration Test
Table (3) presents the slabs which have been tested under penetration by means <strong>of</strong> gun shots.
The following slabs were tested at CANMET explosives laboratories to measure the
penetration depth under gun shots. Four to five shots were executed on the following slabs,
one on each corner and one in the center on the slabs. Figure (5) shows the penetration test.

Fig. (4) Impact Test
Table (3) Slabs to be tested under penetration.
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Paper: ASAT-13-MS-24
Slab Dimension(cm) Reinforcement Concrete dim. <strong>Ferro</strong>cement
SP-1 55×55×10 4�10 U,D 55×55×10 ---------------
SP-2 55×55×14 4�10 U,D 55×55×14 ---------------
SP-3 55×55×14 4�10 U,D 55×55×10 2 layers U,D*
SP-4 55×55×14 4�10 U,D 55×55×10 2 layers U,D**
U = .Upper layer, D = Down layer
*. … 2 layers <strong>of</strong> ferrocement each layer contains 2 meshes
** …2 layers <strong>of</strong> ferrocement each layer contains 4 meshes
2.3.3. Fire Test
Table (4) represents the slabs, which have been tested under fire load. The following slabs
were tested at Carleton University civil laboratory to measure the slabs fire resistance. Figure
(6) shows the fire test.
Table (4) Slabs to be tested under fire.
Slab Dimension(cm) Reinforcement Concrete dim. <strong>Ferro</strong>cement
SF-1 55×55×2.5 ---------------- ----------------- 2 mesh
SF-2 55×55×2.5 ---------------- ------------------ 4 mesh

Fig. (5) Penetration test.
Fig. (6) Fire test.
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Paper: ASAT-13-MS-24
2.3.4. Fire and Penetration Test
A penetration test was applied to the above mentioned slabs that were subjected to the fire
test. Table (5) shows the slabs that were used in the fire and penetration test. Figure (7) Shows
the preparation <strong>of</strong> burned slabs for the penetration test.

Table (5) Slabs to be tested under fire and penetration test.
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Paper: ASAT-13-MS-24
slab Dimension(cm) Reinforcement Concrete dim. <strong>Ferro</strong>cement
SFP-1 55×55×12 4�10 U,D 55×55×10 2 layer U,D* f
SFP-2 55×55×12 4�10 U,D 55×55×10 2 layer U,D** f
S#P-1 55×55×12 4�10 U,D 55×55×10 2 layer U,D*
S#P-2 55×55×12 4�10 U,D 55×55×10 2 layer U,D**
U = Upper layer; D = Down layer
* f 2 layers <strong>of</strong> ferrocement each layer contains 2 meshes and subjected to fire.
** f …2 layers <strong>of</strong> ferrocement each layer contains 4 meshes and subjected to fire.
* 2 layer <strong>of</strong> ferrocement each layer contains 2 meshes.
** 2 layer <strong>of</strong> ferrocement each layer contains 4 meshes.
Fig. (7) Burned slabs ready for penetration test.
3. Results
The response <strong>of</strong> the specimens was examined and recorded.
3.1. Impact
The result <strong>of</strong> impact test was listed in Table (6), and presented as shown in Figs. (8) & (9).
Table (6) Impact test results.
Slab No. <strong>of</strong> blows to failure Max. deflection (mm) Total absorbed energy(J)
SI-1 2 95 2450
SI-2 3 86 3880
SI-3 4 98 5000
SI-4 5 94 6150

Fig. (8) Slabs subjected to impact test.
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Paper: ASAT-13-MS-24
3.2. Penetration
The result <strong>of</strong> penetration test according to velocity <strong>of</strong> projectile (bullet) and the case <strong>of</strong>
penetration was listed in Table (7), and presented as shown in Fig. (10).
Table (7) Penetration test results.
Velocity m/sec Slab SP-1 Slab SP-2 Slab SP-3 Slab SP-4
930 ------------- P ------------ P,P”
640 ------------- S,S P”,S, S,C,C P”, S,C
575 ------------- ------------ S,C ------------
512 P S S,C S,S,C,C
450 S S,S ------------ S,C
P………Projectile penetrated the slabs
P”……..Projectile penetrated the slabs and the cover is lodged
S………Projectile stopped by the slabs
C……...Projectile lodged in the slabs

Energy (J)
Deflection (mm)
Deflection (mm)
7000
6000
5000
4000
3000
2000
1000
0
120
100
80
60
40
20
120
100
80
60
40
20
0
Absorbed Energy by Different Types
<strong>of</strong> Slabs
SI-1 SI-2 SI-3 SI-4
Slabs
Time-Deflection curves for SI-1
0
0 0.2 0.4 0.6 0.8 1
Time (s)
Time-Deflection Curves for SI-3
SI1-2
SI1-1
SI3-1
SI3-2
SI3-3
SI3-4
0 0.2 0.4 0.6
Time (s)
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deflection (mm)
Deflection (mm)
Deflection (mm)
100
80
60
40
20
0
100
80
60
40
20
120
100
80
60
40
20
0
Fig. (9) Impact test results.
Paper: ASAT-13-MS-24
Deflection-Energy curves
Slab SI-1
Slab SI-2
Slab SI-3
Slab SI-4
0 2000 4000 6000 8000
Energy (J)
Time-Deflection Curves for SI-2
0
0 0.2 0.4 0.6
Time (s)
Time-Deflection curves for SI-4
0 0.2 0.4 0.6 0.8 1 1.2
Time (s)
SI2-1
SI2-2
SI2-3
SI4-1
SI4-2
SI4-3
SI4-4
SI4-5

Fig. (10) Slab subjected to penetration test.
3.3. Fire
The result <strong>of</strong> fire test was listed in Table (8), and presented as shown in Fig. (11)
Table (8) Fire test results.
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Paper: ASAT-13-MS-24
Slab
Weight (lb)
Before After
Length (cm) Width (cm)
Thickness
(cm)
SF1 42.5 1b 40.9 55.0 55.0 2.45
SF2 43.0 1b 41.0 55.5 55.0 2.55
Fig. (11) Slabs after fire test.
3.4. Fire-Penetration
The result <strong>of</strong> penetration-Fire test according to velocity <strong>of</strong> projectile (bullet) and the slab after
burning and before, the results were listed in Table (9), and presented as shown in Fig. (12)

Table (9) Fire-penetration test results.
Velocity m/sec SFP-1 SFP-2 S#P-1 S#P-2
512 P S,C S,C S,C
P ----The projectile is passing through the slabs.
S ----The projectile is stooped by the slabs.
C ----The projectile is lodged in the slabs.
4. Conclusions
`
Fig. (12) Slabs after fire-penetration test.
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Paper: ASAT-13-MS-24
4.1. Impact
� In general, the ferrocement layers showed good stiffness, ductility and impact
resistance.
� The impact resistance <strong>of</strong> the ferrocement was improved with higher ratio <strong>of</strong> volume
fraction.
� The drop load depth can be a reasonable indicator <strong>of</strong> cumulative damage in the case <strong>of</strong>
drop impact test.
� The thickness <strong>of</strong> the slabs increases the absorbed energy
� The impact resistance <strong>of</strong> ferrocement is improved with increase in number <strong>of</strong>
meshes/layer
4.2. Penetration
� Within the scope <strong>of</strong> this experimental investigation, there are two modes <strong>of</strong> failure
observed (perforation and scabbing) the mode depends on the thickness <strong>of</strong> the slabs
� <strong>Ferro</strong>cement would effectively resist the impact effects caused by a bullet impact.

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Paper: ASAT-13-MS-24
� In perforation mode, increasing volume fraction does not significantly improve impact
resistance. However, the spalling area is smaller compared to slabs with fewer
numbers <strong>of</strong> meshes or without meshes.
� The advantages <strong>of</strong> using ferrocement can clearly be seen, when slabs fail in scabbing
mode. It was observed that not only the missile perforation was prevented, but also
the damage in front and in back face was reduced significantly.
� In scabbing mode, ferrocement layer catches the bullet and no concrete flies.
4.3. Fire
� The ferrocement layers can resist fire and crack propagation at 700C o for 30 minutes
� Increasing in volume fraction increased the fire resistance effect slabs.
4.4. Fire-Penetration
� The same advantages <strong>of</strong> ferrocement in penetration are as in fire-penetration.
� <strong>Ferro</strong>cement slabs, fire tested, with 2 meshes lays showed less resistance to
penetration compared to non-fire tested slabs. Increasing the volume fraction might
cancel that observation.
5. Recommendations
� <strong>Using</strong> different types <strong>of</strong> meshes.
� <strong>Using</strong> different thickness <strong>of</strong> ferrocement layer.
� <strong>Using</strong> different types <strong>of</strong> weapons.
� Compare the resistance <strong>of</strong> ferrocement to fire with different materials used in this field
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