Chapter Two

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CHAPTER TWO

LITERATURE REVIEW

2.1 General

Steel-reinforced concrete is widely used in construction of buildings,

bridges, decks, etc. The corrosion of the steel reinforcing bars in the concrete

limits the life of concrete structures. Corrosion occurs in the steel regardless

of the inherent capacity of concrete to protect the steel from corrosion;

imposed by the loss of the alkalinity in the concrete or the diffusion of

aggressive ions (such as chloride and sulfate ions) [26]. However, there are

many ways to prevent the penetration of an aggressive ions into the concrete.

Among these methods the use of chemical admixtures.

There are many researches and papers had been published in this field,

therefore, the literature review concerned with the present work can be

divided into three categories that depend on the researches subjects which

included: a) corrosion of steel-reinforced concrete in aggressive

environments, b) effect of reinforcement corrosion on mechanical properties

of concrete, and c) corrosion prevention and remedial of the reinforcement

concrete.

Chapter Two Literature Review

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2.2 Corrosion of Steel in Concrete in Aggressive Environments

Sayed and Sherbini 1984 [27], investigated the factors responsible for

the premature cracking of the reinforced concrete using chemical analysis of

concrete and Microscopic inspection. They found that: a) the presence of a

high concentration of carbonates in the matrix, b) transgranular cracking

emanating from pitting had occurred in the reinforcing steel, c) high

concentration of aggressive ions (carbonates) in addition to calcareous

contaminants had forced the cracking of the concrete as well as the

transgranular cracking of the embedded reinforcing steel.

Cigna, et al. 1993 [28], studied the corrosion behavior of steel

embedded in concrete specimens in the atmosphere and in artificial sea water

using polarization resistance (Rp), corrosion potential, electrical resistivity

and polarization curves. It has been shown that: a) corrosion potential values

strongly depend on the environment and are not necessarily related to the

corrosion behavior; very low potentials do not always indicate a situation of

corrosion risk, b) the type of aggregate used have a great influence on the

corrosivity of the concrete.

Al-Amoudi and Maslehuddin 1993 [29], investigated the effect of

chloride, sulfate and chloride-sulfate solutions on corrosion of steel embedded

in cement paste by measuring corrosion potentials and corrosion current

density using D.C. linear polarization resistance technique. The results

indicated that a) the corrosion activity was very minimal in specimens

immersed in pure sulfate solution, b) the reinforcement corrosion activity was

found to be higher in specimens immersed in chloride-sulfate solution as

compared to those immersed in pure chloride solution, and c) the corrosion

rate of steel was observed to be doubled when the sulfate concentration in

15.7% Cl- solution is increased from 0.55 to 2.1%.


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Rasheeduzzafar, et al. 1994 [30], studied the effect of magnesium-

sodium sulfate environment on the performance of the plain and blended

cements and elucidated the sulfate attack mechanisms on these cements in the

mixed magnesium and sodium sulfate environment for exposure time of two

years. They found that a) the deterioration was observed in all cements, b) the

deterioration is more pronounced in the blast-furnace-slag (BFS) and silica-

fume (SF) cements and it significantly exceeds that observed in plain and fly-

ash-(FA-) blended cements, c) XRD and SEM analyses indicated that the

greater deterioration in BFS- and SF-blended cements may be attributable to

the depletion of the hydrated calcium hydroxide, and d) in the absence of

Ca(OH)2, magnesium ions react more directly and extensively with the

cementitious calcium silicate hydrate to generate gypsum (SO4- containing)

and noncementitious magnesium silicate hydrate resulting in aggravated

deterioration.

Gonzalez, et al. 1995 [31], conducted a study about average local

attack (pits) of reinforcement in chloride-contaminated concrete using natural

corrosion tests and accelerated tests. It was found that the maximum

penetration of localized attack on steel embedded in concrete containing

chlorides is equivalent to about 4-8 times the average general penetration.

Dehwah, et al. 2002 [32], studied the influence of sulfate concentration

and the effect of cation type associated with sulfate ions, namely Na+ and

Mg2+

, on chloride-induced reinforcement corrosion in Portland cement

concretes (with tri calcium aluminates C3A varying from 3.6% to 9.65% by

weight of cement) exposed to mixed chloride and sulfate solutions (with fixed

NaCl at 5% and varying sulfate concentration to represent that noted in the

sulfate-bearing soil and ground water) for a period of 1200 days.

Reinforcement corrosion was evaluated by measuring corrosion potentials and

corrosion current density at regular intervals. The results indicated that the


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presence of sulfate ions in the chloride solution did not influence the time to

initiation of chloride-induced reinforcement corrosion, but the rate of

corrosion increased with increasing sulfate concentration. Furthermore, the

rate of chloride-induced reinforcement corrosion in concrete specimens

exposed to sodium chloride plus magnesium sulfate solutions was found more

pronounced than that observed in the concrete specimens exposed to sodium

sulfate solution.

ZIVICA 2003 [33], studied the common action of carbonation and

chloride causing corrosion of steel reinforcement. The results obtained

showed that: a) carbonation of concrete foregoing the action of chloride

solutions may intensify the process of corrosion of steel reinforcement in

converse sequence of the action of mentioned media and b) at the same time

the sodium chloride solution had been shown as a more aggressive medium

opposite to the calcium and magnesium chloride solutions.

Morris, et al. 2004 [34], conducted a study that based on a correlation

of electrochemical parameters such as corrosion potential (𝐸𝑐𝑜𝑟𝑟) and current

density (𝑖 𝑐𝑜𝑟𝑟) together with concrete resistivity (𝜌) and chloride

concentration data. A relationship between chloride values for rebar corrosion

initiation and resistivity values (indicative of concrete quality) was proposed.

The results showed that: when the electrical resistivity of concrete increases

from 2 to 100 kΩ cm, the value of the chloride threshold (Cl th) increases from

0.44 to 2.32 % relative to the weight of cement.

Garce´s, et al. 2005 [35], studied corrosion rate of corrugated steel

bars and measured at different pH values in solutions simulating chloride

environments. Hydrochloric acid solutions of different pHs were prepared in

order to compare the steel corrosion rates in these solutions with those

observed in ferrous chloride solutions of the same pH. A comparison of


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polarization resistance measurements (Rp) with gravimetrically weight loss

determined was presented. Additionally, a comparison was made between

measurements of AC impedance with those of the Rp method. The results

indicated that the corrosion rate in the studied media follows the general trend

found in other media of similar pH values: corrosion increases in acidic

solutions, remains rather stable for pH range 3–11 and decreases significantly

in highly alkaline solutions.

Poursaee, et al. 2010 [36], had investigated the effect of three different

deicing salts (NaCl, MgCl2, and CaCl2) on the corrosion of steel rebar and

their impact on the durability of the mortar using accelerator corrosion

technique. The results showed that CaCl2 has the most negative effect on the

steel and, in high concentrations, on the integrity of the mortar. While MgCl2

also deteriorates the mortar if used in high concentration, moreover, NaCl has

no apparent effect on mortar durability even in high concentration.

Zhang, et al. 2010 [37], had investigated the corrosion behavior of

steel rebar in simulated pore solutions and gangue-blended cement mortar.

The simulated pore solutions were based on the pore solution composition of

gangue-blended cement. The corrosion behavior of steel rebar in gangue-

blended cement is different from that in simulated solutions. The gangue

cementitious mortar surrounding steel rebar provides stable passivity

environments for steel, leading to a decrease in ion diffusion coefficients.

Alternating current impedance (ACI) analysis results indicated that the

indicator Rc for concrete resistivity is higher for gangue mortar than for

ordinary Portland cement (OPC), which improves its corrosion potential. The

results from energy dispersive X-ray analysis showed more aluminates and

silicates at the rebar interface for gangue-blended cement. These aluminates

improve the chloride binding capacity of hydrates in mortar, and increase the

corrosion protection of steel rebar.


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2.3 Effect of Corrosion on Mechanical Properties of Concrete

Almusallam 2001 [38], conducted a study to assess the effect of degree

of corrosion of reinforcing steel bars of 6 and 12 mm in diameter on their

mechanical properties. The reinforced concrete specimens were corroded and

then removed and tested in tension. The results indicated that the level of

reinforcement corrosion does not influence the tensile strength of steel bars,

calculated on the area of cross-section. However, when the nominal diameter

is utilized in the calculation, the tensile strength is less than the values stated

in the ASTM A 615 requirement of 600 MPa when the degree of corrosion

was 11 and 24% for 6 and 12 mm diameter steel bars, respectively.

Furthermore, reinforcing steel bars with more than 12% corrosion indicates a

brittle failure.

Fang, et al. 2004 [39], evaluate the effects of corrosion on bond and

bond–slip behavior, for a series of specimens with varying reinforcement

corrosion levels between 0% and 9%, and for specimens with and without

stirrups that provide confinement. Pullout tests were carried out to specimens

with both smooth and deformed bars. The tests were included the ultimate

bond strength and free end slip for various degrees of corrosion under pullout

loads. It has been shown that: a) for deformed bars without confinement, bond

strength decreased rapidly as the corrosion level increased; bond strength at

9% corrosion was only one third of that of noncorroded specimens, b) for

deformed bars with confinement, corrosion had no substantial influence on

the bond strength, c) for smooth bar without confinement, there is a change in

effect of the corrosion on the bond strength at a certain level; that is, when

corrosion level was low, bond strength increased as corrosion level increased,

with the ultimate bond strength as much as 2.5 times that of noncorroded,

while bond strength decreased rapidly at higher corrosion levels. The break

point was for corrosion levels of around 2–4%, and d) for smooth bar with


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confinement, bond strength increased as corrosion level increased, up to a

relatively high degree of corrosion. The increase in bond strength could be

observed even at a corrosion level of more than 5%.

Kilinc, et al. 2005 [40], had investigated effects of sulfates on strength

of Portland cement mortars the specimens were subjected to flexural and

compressive strength tests at the ages of 7, 28 and 90 days. The results

showed that the effect of magnesium sulfate was more pronounced when the

concentration of the salt exceeds 6 %. The strength of mortars decreased as

the concentration of the sodium sulfate increased.

Guneyisi, et al. 2005 [41], studied the steel reinforcement corrosion,

electrical resistivity, and compressive strength of concretes having two

different water-cement ratios (0.65 and 0.45) using plain and blended Portland

cements (300 and 400 kg/m3) and subjected to three different curing

procedures (uncontrolled, controlled, and wet curing). An accelerated

impressed voltage setup has been used to investigate the effect of using plain

or blended cements on the resistance of concrete against damage caused by

corrosion of the embedded reinforcement. The resistivity of the cover

concrete had been measured non-destructively by placing electrodes on

concrete surface. The results indicated that: a) the wet curing was essential to

achieve higher strength and durability characteristics for both plain and

especially blended cement concretes, b) the concretes, which received

inadequate (uncontrolled) curing, exhibited poor performance in terms of

strength and corrosion resistance.

Abosrra, et al. 2011 [42], had investigated corrosion of steel bars

embedded in concrete of different compressive strengths (20, 30, and 46

MPa) in a 3% NaCl solution by weight for 1, 7 and 15 days by applying an

external current of 0.4A using portable power supply in order to accelerate the


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chemical reactions. Corrosion rate was measured using polarization technique

and "Pull-out" tests of reinforced concrete specimens were then conducted to

assess the corroded steel/concrete bond characteristics. It was found that the

corrosion rate of steel bars and bond strength between corroded steel/concrete

are dependent on concrete strength and accelerated corrosion period. As

concrete strength increased from 20 to 46 MPa, corrosion rate of embedded

steel decreased. They observed in first day of corrosion acceleration a slight

increase in steel/concrete bond strength, whereas severe corrosion after 7 and

15 days of corrosion acceleration significantly reduced steel/concrete bond

strength and presence of localized corrosion pits and severe grooves of steel

bars after 7 and 15 days, respectively were observed.

Apostolopoulos, et al. 2013 [43], had investigated the effects of

chloride-induced corrosion, in terms of mechanical properties and pit

depths on steel bars embedded in concrete (embedded samples) and directly

exposed (bare samples), immersed in a salt spray chamber. The results

indicate that: for the same level of mass loss, degradation of the ‘‘embedded

samples’’ was found to be much more severe than that of the ‘‘bare samples’’,

in terms of losses in yield strength and uniform elongation, and b) analysis of

the statistical significance of the pit depth and area values measured, based on

a methodology developed using advanced imaging analysis, indicate that

degradation of the steel bars embedded in concrete produced a more severe

pitting corrosion in terms of depth of pitting, compared to the steel samples

directly exposed to the same corrosive medium, for the same (on average)

mass loss.

2.4 Corrosion Prevention and Remedial of Steel in Concrete

Mor and Mehta, 1984 [44], carried out a preliminary investigation to

clarify the effect of HRWRA admixtures on cement hydration. Concrete


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mixtures of constant w/c ratio were made with ASTM Type I Portland cement

and two types of HRWRA, namely a naphthalene formaldehyde condensate

and melamine formaldehyde condensate. The amount of HRWRA in concrete

was 1, 2 or 3 percent by weight of cement. They concluded that the test at 7

and 28 days give compressive strength higher by 5 to 10 %, compared with

the reference concrete. However, test on the 7-month age specimens showed

that the strength advantage had disappeared. All specimens were partially

submerged in Cl-+SO4

= solution at concentration identical to those present in

severe aggressive environment. Results indicated that, under the action of

aggressive solution, HRWRA concrete showed considerable improvement in

compressive strength, splitting tensile strength, electrodynamics modulus of

elasticity and electrical resistance at all ages compared to reference concrete.

Lukas 1987 [45], discussed the influence of HRWRA concrete on

chloride diffusion. Concrete mixes with cement content of 350 kg/m3 and w/c

ratio of 0.49, slump of 214 mm was prepared. HRWRA concrete was also

prepared using 1.57% Melment L10 HRWRA with the same composition as

the reference concrete. After one day preliminary storage in their moulds, the

samples were stored in a water bath for 7 days and then in the open air until

exposure to chloride solution to one side of the specimens by partial

submersion. The concentration of the solution was 3% by mass of sodium

chloride. Results indicated that the penetrated chloride content decreases with

reduction in w/c ratio. They also concluded that HRWRA concrete has a

smaller tendency to absorb chloride than reference concrete of the same w/c

ratio.

Dhir, et al. 1987 [46], studied the effect of a HRWRA on the durability

potential of normal-workability concrete, 75±10 mm slump. The rate of

carbonation and the chloride ion diffusion were also studied to examine the

corrosion risk of embedded steel in concrete. The investigation was based on


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cement-reduced concrete mixes covering a range of 28 days strength from 20

to 65 N/mm². CONPLAST 337 admixture was used as a HRWRA at an

optimum dosage of 1.5% by weight of cement. They found that the rate of

carbonation and chloride ion diffusion were lower for the HRWRA concrete

than the corresponding reference concrete for equal workability and strength.

This means that the use of a HRWRA admixture can effectively minimize a

corrosion risk of embedded steel in concrete.

Lee, et al. 2000 [47], conducted an experimental study on the

simulation of corrosion in large-scale reinforced concrete columns and their

repair using carbon fiber reinforced polymer (CFRP) sheets. Seven columns

were subjected to an accelerated corrosion regime, wrapped using CFRP

sheets, then tested to structural failure and (or) subjected to further post-repair

accelerated corrosion, monitoring, and testing. Accelerated corrosion was

achieved by adding sodium chloride to the mixing water, applying a current to

the reinforcement cage, and subjecting the specimens to cyclic wetting and

drying. Results showed that: a) the CFRP repair greatly improved the strength

of the repaired member and retarded the rate of post-repair corrosion, and b)

subjecting the repaired column to extensive, post-repair corrosion resulted in

no loss of strength or stiffness and only a slight reduction in the ductility of

the repaired member.

Al-Hubboubi 2001 [48], had investigated the effectiveness of the

HRWRA with respect to electrochemical behavior of embedded reinforcing

steel in concrete. Reference concrete containing 550 kg/m3 cement, w/c = 0.39

and slump of 100 mm was prepared. 5.5% Melment L10 by weight of cement

was used to prepare HRWRA concrete. The specimens were partially

submerged in Cl- +SO4

- - solution. The strength development and initial

surface absorption were investigated for reference and HRWRA concrete. The

A.C electrical resistance, half-cell potentials and corrosion currents were


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examined. Results demonstrated that the incorporation of HRWRA led to a

considerable improvement in strength and great reduction in initial surface

absorption and corrosion activity after 180 - 240 days of exposure.

Memon, et al. 2002 [49], had investigated the effects of mineral and

chemical admixtures namely fly ash, ground granulated blast furnace slag,

silica fume and superplasticizers on the porosity, pore size distribution and

compressive strength development of high-strength concrete in seawater

curing condition exposed to tidal zone. In this study, three levels of cement

replacement (0%, 30% and 70% by weight) were used. They found that: a)

the pore size distribution of high-strength concrete was significantly finer and

the mean volume pore radii (MVPR) at the age of 6 months were reduced

about three times compared to normal Portland cement (NPC) concrete, b)

both concrete mixes (30% and 70%) exhibited better performance than the

NPC concrete in seawater exposed to tidal zone, and c) high-strength concrete

produced would withstand severe seawater exposure without serious

deterioration.

Sun, et al. 2004 [50], studied the influences of the types, amount and

adding approaches of mineral admixtures on pH values, electrical resistance

of concrete, anodic polarization potential and mass loss ratio of steel bars in

concrete subjected to 50 immersion–drying cycles were. The testing results

showed that: a) the addition of mineral admixtures reduced the pH values of

the binder pastes in green high performance concrete (GHPC), especially

when two or three types of mineral admixtures were added at the same time

(double- or triple adding approaches), whereas the final pH values were still

above the critical breakage pH value of passivation film on the steel bar

surface (11.5), b) double- and triple-adding approaches also greatly increased

the electrical resistance of concrete, which led to a delay in the initial time of

corrosion and a decrease in the corrosion rate of steel bars, and c) fly ash can


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reduce the corrosion of steel bars when a large amount of fly-ash replacement

was used.

Lawrence, et al. 2005 [51], studied the effect of different kinds of

mineral admixtures on the compressive strength of mortars made with up to

75% of crushed quartz, limestone filler or fly ash of different fineness. They

found that: a) for short hydration times (1 to 2 days), the nature of mineral

admixture is not a significant parameter, as mortars containing the same

amount of different kinds of admixtures having equivalent fineness present

similar strengths, b) for long hydration times (up to 6 months), the excess

strength due to fly ash pozzolanic activity is quantified by the difference

between the strengths of mortars containing the same proportions of inert and

pozzolanic admixtures with the same fineness. In the case of inert mineral

admixtures, the increase in strength with the fineness of mineral admixtures

cannot be explained by the filler effect, but can be attributed to the physical

effect of heterogeneous nucleation.

Prabakar, et al. 2009 [52], conducted an experimental study to

evaluate the effect of Sodium Nitrate as a corrosion inhibitor in concrete with

1%, 2%, 3%, and 4% by weight of cement. Durability properties such as

Rapid Chloride Penetration Test (RCPT) were studied. Compressive strength,

flexural and split tensile strengths were also studied. The results showed that:

a) durability properties enhanced and further with increase in corrosion

inhibitor dosage. Concrete with 4% Sodium Nitrate had got 1.8 times better

performance as compared to normal concrete, and b) the mechanical

properties of concrete also enhanced with adding of Sodium Nitrate.

Hassan, et al. 2009 [53], had investigated the corrosion of steel

reinforcement embedded in full-scale self-consolidating concrete (SCC)

beams was compared to normal concrete (NC). Beams containing epoxy- and


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non-epoxy-coated stirrups were monitored under an accelerated corrosion

test. The corrosion performance of NC/SCC beams was evaluated based on

the results of current measurement, half-cell potential tests, chloride ion

content, mass loss and bar diameter degradation. The investigation also

included the effect of admixture type and the size of specimen on corrosion

performance. In general, SCC beams showed superior performance compared

to their NC counterparts in terms of corrosion cracking, corrosion

development rate, half-cell potential values, rebar mass loss and rebar

diameter reduction. They found that: a) SCC beams showed localized

corrosion with concrete spalling due to non-uniform concrete properties along

the length, which was a result of the casting technique, b) difference between

SCC and NC mixes in terms of corrosion was more pronounced in large-scale

beams, and c) types of admixture used in SCC have no influence on corrosion

performance.

Al-Mehthel, et al. 2009 [54], conducted a study to evaluate the

improvement in corrosion-resistance of chloride-contaminated silica fume

cement concrete due to the use of corrosion inhibitors. Three proprietary and

one generic corrosion inhibitors were evaluated for their performance in

inhibiting reinforcement corrosion in the silica fume cement concrete

specimens contaminated with 0.4%, 1%, and 2% chloride concentration, by

weight of cement. Potentials corrosion and accelerated corrosion methods

were used. It has been shown that: a) the extent of corrosion increased with

increasing chloride contamination in the concrete specimens, b) incorporation

of inhibitor decreased the rate of reinforcement corrosion. The rate of

reinforcement corrosion in the concrete specimens incorporating an organic

inhibitor that was added to the concrete during mixing was the least followed

by that in the concrete specimens on which a penetrating corrosion inhibitor


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was applied, and c) the accelerated impressed current technique was noted to

be suitable for quickly screening the performance of corrosion inhibitors.

Xie, et al. 2012 [55], investigated rehabilitation of corrosion-damaged

reinforced concrete (RC) beams with carbon fiber reinforced polymer

(CFRP), which focus on the effectiveness of CFRP-repaired methods and the

effects of CFRP amount on flexural behavior of the beams. A modified

retrofit method based on substrate repairs was developed, which is bonding

CFRP after replacing V-notch of substrate concrete with polymer mortar. To

compare the modified method with two common retrofit methods, which are

respectively bonding directly CFRP and bonding CFRP after replacing

damaged concrete, four-point bending experiments were conducted on a

series of corrosion-damaged RC beams with CFRP. Important factors were

considered in the experimental study, including the number of CFRP layers

and corrosion level denoted by the mass loss rate of tensile steel. The results

show that: a) the modified retrofit method could provide better load carrying

capacity for the beams having more than 15% mass loss of tensile steel, b) the

simple method of directly bonding CFRP was suitable for the beams having

less than 15% mass loss of tensile steel, and c) by optimizing the amount of

CFRP, it is possible to balance strength recovery with control of failure mode.


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2.5 Concluding Remarks

From the review of above previous literature works concerned with

reinforcement concrete, the following remarks can be summarized as follow:

1. Intensive electrochemical investigations concerned with corrosion of

embedded steel in concrete exposed to corrosive environments such as

chloride, sulfate, and acidic solutions.

2. In the review of the previous work on monitoring of reinforcement

corrosion in concrete, most of the researchers using half-cell potential

method, accelerated corrosion technique, linear polarization resistance

measurements, x–ray diffraction, and scanning electron microscopy.

3. Limited studies were carried out to study the effect of polymeric

compounds on corrosion activity of embedded steel in concrete structures.

4. The research work concerned with the use of plastocrete-N polymer was

restricted for improving compressive strength only. While the present

study aimed to justify the use of such polymeric material as corrosion

inhibitor for steel reinforcement.

Chapter Two

Documents

corrosion of steel

corrosion behavior of

corrosion potentials

corrosion rate of steel

reinforcement concrete

concrete specimens

concrete limits

c corrosion prevention