1. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May - June (2013), © IAEME
176
EFFECT OF CORROSION ON CONCRETE REINFORCEMENT
MECHANICAL AND PHYSICAL PROPERTIES
Sanad A.M.1
and Hassan H.A.2
(Construction & Building Department, College of Engineering & Technology,
Arab Academy for Science, Technology & Maritime Transport, Cairo, Egypt)
ABSTRACT
Corrosion of concrete reinforcement is a major factor affecting the deterioration of
RC structures. During corrosion, steel undergoes several phases of chemical reactions with
consequent variation in steel section geometry and mechanical properties. At ultimate
corrosion stage, the effective cross section area of steel is reduced with equivalent decrease in
load carrying capacity leading to unsafe structures. During initial phase of corrosion,
chemical reactions generate new products which irregularly increase bars’ diameters. The
resulted products induce additional stresses on the structural member, causing cracking and
spalling of the concrete cover. Corrosion cracking increases further corrosion rate by loss of
protective cover and direct exposure to corrosive environment. A comprehensive
experimental program was conducted to evaluate the effect of several degrees of corrosion on
the mechanical and physical properties of concrete reinforcement bars. Three types of carbon
steel bars were used: plain, deformed, and epoxy-coated deformed bars. The results showed
clearly the effect of corrosion on increasing the rate of deterioration of RC members’
strength.
Keywords: Steel corrosion, Reinforced Concrete Deterioration, Mechanical Properties.
1. INTRODUCTION
Recently the aspects of concrete durability and performance have become a major
subject of discussion especially when the concrete is subjected to severe environment.
Corrosion of steel bars is the main factor influencing both the concrete durability and strength
[1]. The corrosion products of the steel reinforcement can expand four to five times its
original volume, developing high pressures within the concrete, which cause cracking and
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2. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May - June (2013), © IAEME
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spalling of the concrete cover and expose the rebar to further corrosion activity. The potential
consequences of the corrosion problem can be summed up in the continuous reduction in
strength, stiffness, durability and designed life time of concrete structural elements reinforced
with conventional steel. According to the ASTM [2], corrosion is defined as “the chemical or
electrochemical reaction between a material, usually a metal, and its environment that
produces a deterioration of the material and its properties”. Corrosion reduces the ribs height
of the deformed bar which causes reduction in the contact area between the ribs and the
concrete leading to reduction in the bond strength. Corrosion may also affect the rib face
angle in the advanced stages; moreover, ribs of deformed bars are eventually lost at high level
of corrosion. Corrosion of reinforced bars is usually associated with the increase of the crack
width [3]. The increase of the corrosion products around the bar leads to increase of bursting
force and tension cracking of the surrounding concrete, as the corrosion increases, the crack
width becomes wider and the bond strength decreases [4].
Rapid deterioration of reinforced concrete buildings in Alexandria, Egypt has become
a major problem for sea front buildings’ dwellers, where the disaster exceeds the value of
money and extends to human lives. In the last decade many reinforced concrete buildings
collapsed with a majority located in coastal cities. Over eighty percent of these collapses
were at Alexandria and Damietta which are located at the north coast of Egypt facing the salt
attack of the Mediterranean Sea. This high percentage highlights the importance of
investigating the common factors that lead to the collapse of those buildings [1].
2. RESEARCH SCOPE AND OBJECTIVES
The main objective of this paper is to study the rate of reinforcement corrosion for
three different types of steel embedded in four types of concrete. The effect of corrosion on
the mechanical & physical properties of the embedded reinforcement is also investigated and
the study is conducted at four phases of corrosion; un-corroded bars, pre-cracking, cracking
and severely corroded bars. A comprehensive experimental program was implemented to
identify the effect of four parameters; the water/cement ratio, concrete strength, type of steel
reinforcement and coating material. The tested mechanical properties included the loss of the
tensile strength and steel bars’ ductility; where, the measurement of physical properties
included the mass and rib height loss of the bars.
3. EXPERIMENTAL PROGRAM
The effect of steel corrosion on the durability of seafront reinforced concrete
structures was investigated experimentally at AASTMT Labs where the four types of
concretes considered had variable water/cement ratios and variable ultimate strengths as
shown in Table 1. The effect of corrosion in regular carbon steel bars was evaluated for Plain
bars, un-coated deformed bars and epoxy coated deformed bars. The bars diameter was
16mm and used to reinforce a 100mm diameter by 200mm height concrete cylinder. The
specimen was reinforced with a single bar located in the center as shown in Fig. 1.

3. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May
Table 1:
Mixture
Type
Concrete Density
(kN/m3
)
30MPa,
w/c=0.32
23.1
44MPa,
w/c=0.32
23.3
60MPa,
w/c=0.32
23.3
44MPa,
w/c=0.52
24.2
Figure 1.
Different dosages of super plasticizers were added to the mixtures having low water
cement ratios (w/c=0.32) to obtain
mixture with high water cement ratio (w/c=0.52). This technique was used to investigate
separately the effect of concrete strength and the effect of water cement ratio without any
other variable that might affect the mechanical properties of the concrete. The tested
mechanical and physical properties of the used steel bars before corrosion initiation are
shown in Table 2.
nternational Journal of Civil Engineering and Technology (IJCIET), ISSN 0976
6316(Online) Volume 4, Issue 3, May - June (2013), © IAEME
178
Table 1: Test results for concrete specimens
Slump
(mm)
Test Type
Average Stress of
three samples (after
56 days) (MPa)
29
Compressive Strength 33.74
Splitting Tensile Strength
30
Compressive Strength 48.58
Splitting Tensile Strength
33
Compressive Strength 62.90
Splitting Tensile Strength
32
Compressive Strength 49.88
Splitting Tensile Strength
Figure 1. cylinderical concrete specimens
Different dosages of super plasticizers were added to the mixtures having low water
cement ratios (w/c=0.32) to obtain approximately the same slump range as the 44MPa
mixture with high water cement ratio (w/c=0.52). This technique was used to investigate
separately the effect of concrete strength and the effect of water cement ratio without any
fect the mechanical properties of the concrete. The tested
mechanical and physical properties of the used steel bars before corrosion initiation are
nternational Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
June (2013), © IAEME
Average Stress of
three samples (after
56 days) (MPa)
33.74
3.69
48.58
4.60
62.90
4.40
49.88
3.98
Different dosages of super plasticizers were added to the mixtures having low water
approximately the same slump range as the 44MPa
mixture with high water cement ratio (w/c=0.52). This technique was used to investigate
separately the effect of concrete strength and the effect of water cement ratio without any
fect the mechanical properties of the concrete. The tested
mechanical and physical properties of the used steel bars before corrosion initiation are

4. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May
Table 2: Tested mechanical and physical properties of steel bars
16mm un coated
plain steel bars
Steel Grade
Code PL
Effective diameter
Yield stress (MPa)
Tensile strength (MPa)
Elongation percentage
4. ACCELERATED CORROSION
Accelerated corrosion tests are used to obtain qualitative information on corrosion
behavior in a relative short period compared to the field corrosion test. Accelerated corrosion
tests have been used successfully to determine the susceptibility of the reinforcing and other
forms of structural steel to localized attacks such as pitting corrosion, stress corrosion and
other forms of corrosion [5]. Before testing, all concrete samples were
months and specimens tested at end of this period were defined as zero corrosion samples and
served as the control specimens. The rest of specimens were placed in fiber tank with
dimension 165x85 cm containing an electrolytic solution
weight of water]. A steel mesh was placed in the bottom of tank to carry the specimens and
connected to 12V power supply through a single steel bar as shown schematically in Fig. 2.
The direction of electrical current was ar
while the specimens’ bars served as anodes.
Based on the crack width; three corrosion phases were defined; Pre
considered when the electrical current measurement started to increase but
was visible. Cracking stage considered when the first crack appeared on the concrete
specimen regardless its width, and severe corrosion stage considered when any crack width
reached 4mm. The accelerated corrosion test was terminated when al
took place for all steel types.
Figure 2: schematic diagram showing the accelerated corrosion set
nternational Journal of Civil Engineering and Technology (IJCIET), ISSN 0976
6316(Online) Volume 4, Issue 3, May - June (2013), © IAEME
179
Tested mechanical and physical properties of steel bars
16mm un coated
plain steel bars
16mm un coated
deformed steel bars
16mm epoxy coated
deformed steel bars
24/35 40/60 40/60
PL-UC DF-UC DF
16 15.75 15.85
250 564.5 546.5
360 676 658
21.9 13 12.5
CORROSION SET-UP
Accelerated corrosion tests are used to obtain qualitative information on corrosion
behavior in a relative short period compared to the field corrosion test. Accelerated corrosion
have been used successfully to determine the susceptibility of the reinforcing and other
forms of structural steel to localized attacks such as pitting corrosion, stress corrosion and
other forms of corrosion [5]. Before testing, all concrete samples were set for curing for 2
months and specimens tested at end of this period were defined as zero corrosion samples and
served as the control specimens. The rest of specimens were placed in fiber tank with
dimension 165x85 cm containing an electrolytic solution [5% sodium chloride NaCl by the
weight of water]. A steel mesh was placed in the bottom of tank to carry the specimens and
connected to 12V power supply through a single steel bar as shown schematically in Fig. 2.
The direction of electrical current was arranged so that the single steel bar served as cathode,
while the specimens’ bars served as anodes.
Based on the crack width; three corrosion phases were defined; Pre-cracking stage
considered when the electrical current measurement started to increase but before any crack
was visible. Cracking stage considered when the first crack appeared on the concrete
width, and severe corrosion stage considered when any crack width
The accelerated corrosion test was terminated when all stages of corrosion
chematic diagram showing the accelerated corrosion set-up
nternational Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
June (2013), © IAEME
16mm epoxy coated
deformed steel bars
40/60
DF-C
15.85
546.5
658
12.5
Accelerated corrosion tests are used to obtain qualitative information on corrosion
behavior in a relative short period compared to the field corrosion test. Accelerated corrosion
have been used successfully to determine the susceptibility of the reinforcing and other
forms of structural steel to localized attacks such as pitting corrosion, stress corrosion and
set for curing for 2
months and specimens tested at end of this period were defined as zero corrosion samples and
served as the control specimens. The rest of specimens were placed in fiber tank with
[5% sodium chloride NaCl by the
weight of water]. A steel mesh was placed in the bottom of tank to carry the specimens and
connected to 12V power supply through a single steel bar as shown schematically in Fig. 2.
ranged so that the single steel bar served as cathode,
cracking stage
before any crack
was visible. Cracking stage considered when the first crack appeared on the concrete
width, and severe corrosion stage considered when any crack width
l stages of corrosion

5. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May - June (2013), © IAEME
180
5. EXPERIMENTAL PROGRAM RESULTS
The results of this research are divided into two parts; the first concerning the effect of
corrosion on the mechanical properties of the reinforcing bars including the yield stress, the
tensile strength and the ductility. The second part shows the effect of corrosion on the
physical properties including the mass, the rib height, and the cross-sectional area of the bars.
5.1 Effect of Corrosion on the Bars’ Mechanical Properties
The corroded bars were removed from the samples, after performing a pull-out test
for concrete-reinforcement bond strength. Then, theywere subjected to axial tensile test to
study the effect of corrosion on the tensile strength and ductility of the bars. The stress-strain
curves were plotted for each concrete and steel type at different degrees of corrosion. Figs. 3
to 5 show an example of stress-strain behaviors for the bars embedded in the 44MPa, 0.52
water/cement ratio concrete cylinders.The tensile stress was calculated by dividing the tensile
load by the average cross sectional area of bar, taken as the average between the area of the
corroded embedded part and the un-corroded area of the protruding part. The strain was
calculated by dividing the extension values taken from the machine LVDT by the bar initial
length.From the figures, it can be seen that corrosion affects the steel mechanical properties
negatively. At zero corrosion stage, all bars showed large ductility and high yield stress.
However, these ductility regions start to disappear as the corrosion propagated from pre-
cracking to severe corrosion stage and all bars failed at lower extensions due to large decrease
in ductility.Nearly all steel grades showed similarreduction in ductility values.
Figure 3: stress-strain curve for un-coated plain bars
0
50
100
150
200
250
300
350
400
0 0.05 0.1 0.15 0.2 0.25
Tensilestress(Mpa)
Strain (mm/mm)
Zero corrosion
Pre-cracking
Cracking
Severe corrosion

6. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May - June (2013), © IAEME
181
Figure 4: stress-strain curve for un-coated deformed bars
Figure 5: Stress-strain curve for epoxy-coated deformed bars
A clear reduction in yield stress and ultimate stress is also observed in all specimens.
As corrosion propagates, the safety factor used in the designing process is drastically reduced
due to the decrease in yield stress and the over-all advantage of structural ductility also
disappears, leading to sudden failure without signs of large deformation in the structure.
Corrosion of steel over whelms its advantages when the effective cross section is reduced, the
ultimate stress is decreased and the ability for large elongation at yield limit is lost.
0
100
200
300
400
500
600
700
800
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14
Tensilestress(Mpa)
Strain (mm/mm)
Zero corrosion
Pre-cracking
Cracking
Severe corrosion
0
100
200
300
400
500
600
700
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09
Tensilestress(Mpa)
Strain (mm/mm)
Zero corrosion
Pre-cracking
Cracking
Severe corrosion

7. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May - June (2013), © IAEME
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5.2 Effect of Corrosion on the Bars’ Physical Properties
The effect of corrosion on steel bars physical properties was studied including the
mass and rib loss for each type of steel at different degrees of corrosion. The mass loss was
obtained as the difference between the mass of the corroded bar, after removal of the loose
corrosion products, and its mass before corrosion. The ribs height were measured after the
corrosion took place, and the rib profile loss was obtained as the difference between the rib
height of the corroded bar and its height before corrosion. Tables 3 and 4 show the mass and
rib profile loss of steel bars at different corrosion stages respectively.
Table 3: Mass loss of steel bars at different degrees of corrosion
Concrete
Type
Steel Type
Mass loss as a percentage of zero corrosion
mass (%)
Pre-cracking Cracking Severe Corrosion
30MPa,
w/c=0.32
Plain (St37) 0.8 2.6 3.5
Deformed Uncoated (St60) 1.2 2.9 4.2
Deformed Coated (St60) 1.6 2.4 3.6
44MPa,
w/c=0.32
Plain (St37) 0.4 0.6 2.9
Deformed Uncoated (St60) 1 1.2 3.6
Deformed Coated (St60) 1 1.1 3.3
60MPa,
w/c=0.32
Plain (St37) 0.4 1.2 2.2
Deformed Uncoated (St60) 0.5 1.7 2.9
Deformed Coated (St60) 0.4 1.7 2.6
44MPa,
w/c=0.52
Plain (St37) 0.6 2.6 3.7
Deformed Uncoated (St60) 0.4 1.6 4.2
Deformed Coated (St60) 0.5 2.9 4.1
From Table 3, the un-coated deformed bars have the greatest mass loss while the plain
bars have the least mass loss in all concrete mixes. The epoxy coated bars have less mass loss
compared to the uncoated deformed bars which proves the efficiency of the epoxy coating in
corrosion protection. The epoxy coating is well known for its good protection for steel bars
against corrosion. The epoxy coating in this research was applied to the whole length of the
bar but its ends were left un-coated as practiced in the construction field. Therefore the
corrosion is concentrated in the uncoated end leading to specific core rupture across the
diameter. Figs. 3 and 4 show the difference in crack propagation between the un-coated and
epoxy coated deformed bars respectively. The comparison between the un-coated deformed
bars and plain bars, showed that the plain bars have less mass loss than the deformed ones.
This can be related to the high surface area of deformed bars. The plain bars had also less
mass loss than the deformed coated ones. The plain bars are steel 37, while the deformed bars
are steel 60, therefore the difference in corrosion rate can be attributed to the difference in

8. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May - June (2013), © IAEME
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chemical composition between the two types of steel, showing that steel 37 is more resistant
to corrosion than steel 60. The uncoated bars also showed uniform corrosion along the total
bar length, while the epoxy coated bars showed concentrated corrosion at un-coated end
leading to localized stresses at the bottom third of the concrete cylinder.
Table 4: Rib and diameter loss of steel bars at different degrees of corrosion
Concrete
Type
Steel Type
Rib profile loss as a percentage of zero corrosion
rib height (%)
Pre-cracking Cracking
Severe
Corrosion
30MPa,
w/c=0.32
Plain St37(diameter loss)* 8.7 16.1 18.8
Deformed Uncoated St60 69.2 98.56 (131.2)**
Deformed Coated St60 81.2 92.1 (122.1)**
44MPa,
w/c=0.32
Plain ST37 (diameter loss)* 6.1 7.5 17.1
Deformed Uncoated St60 38.7 69.6 (121.9)**
Deformed Coated St60 43.6 66 (116.9)**
60MPa,
w/c=0.32
Plain ST37 (diameter loss)* 6 11.1 14.7
Deformed Uncoated St60 47.2 84.7 (108.4)**
Deformed Coated St60 40.8 83.6 (103.9)**
44MPa,
w/c=0.52
Plain ST37 (diameter loss)* 7.6 16 19.1
Deformed Uncoated St60 63.9 81.8 (132.1)**
Deformed Coated St60 63.1 94.2 (130.9)**
*For plain bars with no ribs, the percentages were calculated from the total cross-sectional
area of the bar.
**Results exceeding the 100% indicate that the corrosion causes total loss in the ribs and
extends to the inner bar diameter.
Figure 6 Crack propagation in concrete
cylinders reinforced with uncoated
defromed bars
Figure 7 Crack propagation in concrete
cylinders reinforced with epoxy coated
defromed bars

9. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 3, May - June (2013), © IAEME
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Concerning the rib height loss, Table 4 indicates that un-coated deformed bars exhibit
the maximum rib loss when compared to the plain and epoxy coated deformed bars. From the
previous two tables, it can be concluded that the rate of corrosion increases in case of un-
coated deformed bars. This can be attributed to the greater surface area of deformed bars
compared to the plain bars and their greater conductivity when compared to the epoxy coated
bars, where the epoxy acts as a barrier to chloride penetration.
6. CONCLUSION
The purpose of this research is to study the effect corrosion on reinforced concrete
structures especially those near the sea side and structures located in salt-laden environments.
The influence of corrosion on the mechanical and physical properties of steel bars was
investigated. This paper includes results from experimental program performed with four
concrete mixes and three types of steel bars. All concrete mixes were reinforced by three
different carbon steel types: Plain, deformed, and epoxy-coated deformed bars. The
experimental results of steel bars tensile tests, showed that all bars demonstrate large ductility
at yielding regions before corrosion. However, these regions starts to disappear as the
corrosion propagated from pre-cracking to severe corrosion. At advanced corrosion stages;
corrosion reduces the cross-sectional area of steel bars, and affect the height of ribs of
deformed bars. Corrosion causes high loss of steel ductility, large reduction of yield and
ultimate stresses. When combined with reduction of effective cross-sectional area of steel,
corrosion leads to serious deterioration of load carrying of reinforced concrete members.
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[3] Bertolini, L., (2004), “Corrosion of Steel in Concrete,” ISBN: 3-527-30800-8.
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