Page 1 of 8

Journal for Studies in Management and Planning

Available at

http://edupediapublications.org/journals/index.php/JSMaP/

e-I SSN: 2395-0463

Vol ume 02 I s s ue 9

September 2016

Available online: http://edupediapublications.org/journals/index.php/JSMaP/ P a g e | 152

Service Life Estimation of Reinforced Cement

Concrete Structure Induced By Chloride Ions

1M. MADHUBABU, 13FF1D8710, madhu19862000@gmail.com

Mandava Institute of Engineering and Technology,

Vidya Nagar, Krishna District, Jaggayyapet, Andhra Pradesh, 521175

2Mr. D. Aditya Sairam, M-Tech. Associate Professor

Abs tract:

Concrete is the most versatile and unique material

for building industry. The service life of the concrete

sometimes reduced due to deterioration caused by

the various environmental factors. The rate of

deterioration may have very high when the steel used

in concrete starts corroding. The Corrosion induced

deterioration in reinforced cement concrete structure

is a common and recurring problem in the world. A

durable concrete can provides an excellent service to

maintain its expected strength and service life. In the

past several decades, the research approach had been

limited to the strength of concrete, but due to the

emerged harsh environment, in recent years, research

has been focused towards the durability and long- term performance of concrete structures.

This study aims to formulate a method to

determine the service life estimation of Reinforced

Cement Concrete (RCC) structures based on the

experimental data generated by conducting various

durability tests using different grades of concrete

with and without mineral and chemical admixtures.

The scope of the work involves studying the

durability properties such as chloride diffusion,

Rapid Chloride Penetration Test (RCPT), Water

Permeability, Resistivity and Accelerated corrosion

test for different grades of concretes with and

without mineral admixtures to formulate a

relationship among the durability parameters for

estimating the service life of reinforced concrete.

This study also covers the effect of concrete cover

thickness, concrete surface coatings, corrosion

resistance steel and corrosion inhibitors on

durability. Durability properties have been studied

for concrete grades varying from M25 to M75 with

mineral admixtures such ash fly ash and Ground

Granulated Blast Furnace Slag (GGBS) in

comparison with control concretes of similar grades.

Corrosion Inhibitors such as Calcium Nitrate,

Sodium Nitrite and Monoethanolammine were used

by adding 1 to 4 % by mass of cement in M40 grade

concrete and the effect on durability on concretes

were studied. Accelerated corrosion initiation time

study was carried out on concrete specimens and the

effect of concrete cover thickness also conducted

using different size cylindrical moulds and re-bars to

give a clear cover thickness of 29.5 mm, 40 mm, 46

mm, 59 mm, and 70 mm. From the results of

durability study, the constitutional relationship

among RCPT, Chloride Diffusion, Water

Permeability, Resistivity and Accelerated Corrosion

Initiation Time has been formulated. From this co- relation, an equation has been obtained which helps

to estimate the service life of reinforced cement

concrete structures made with materials of similar to

what has been used in the study. Based on this

experimental results and co-relationship between

durability properties, a model has been developed

using MATLAB program to estimate the service life

of reinforced concrete structure. The model has been

validated with the experimental results carryout on

concretes especially for validation and found very

good.

Keywords

Corrosion, Reinforced Cement Concrete (RCC),

Rapid Chloride Penetration Test (RCPT), Ground

Granulated Blast Furnace Slag (GGBS), reinforced

concrete structure.

1. Introduction

During the past several decades, concrete

structures had suffered from safety and serviceability

problems due to deterioration of concrete.

Generally concrete is a very durable material, the

environmental factors such as weathering action,

chemical attack, abrasion and other deterioration

process may change the properties of concrete with

time when rebar is embedded into the concrete.

The deterioration of Reinforced Cement Concrete

(RCC) Structures is due to the corrosion of steel used

in concrete. Corrosion of reinforcing steel results in

the build-up of voluminous corrosion products

generates internal stresses which lead to cracking and

spalling of the cover concrete. The main causes of

Page 2 of 8

Journal for Studies in Management and Planning

Available at

http://edupediapublications.org/journals/index.php/JSMaP/

e-I SSN: 2395-0463

Vol ume 02 I s s ue 9

September 2016

Available online: http://edupediapublications.org/journals/index.php/JSMaP/ P a g e | 153

rebar corrosion are due to ingress of chloride ions or

diffusion of CO2 gas from atmosphere. A lowering

of the pH by penetration of free chloride ions though

the concrete cover to the steel, or by the carbonation

of the concrete cover due to penetration of

atmospheric carbon dioxide, can cause breakdown of

the passive layer.

In general, good quality concrete provides an

excellent protection for steel reinforcement. The steel

used in concrete are remains in passive state due to

high alkalinity of concrete. The time to initiate

corrosion is determined largely by the amount and

the quality of concrete, cover thickness as well as

permeability of concrete. Once de-passivation

occurs, corrosion propagation is governed by anodic,

cathodic and/or electrolytic properties of corrosion

cell. The rate of chloride diffusion is influence in

concrete with w/b, ratio and the properties of paste

such as type of cement, mix ratio and percentage of

supplementary cementing material, temperature and

humidity.

Objective and Scope of Res earch:

The Main Objectives of this thesis are to:

i. Study the various durability properties such

as chloride diffusion, RCPT, permeability, resistivity

and corrosion initiation time of different types and

grades of concretes with and without mineral

admixtures.

ii. Study the effect of concrete cover thickness

in different types and grades of concrete on corrosion

initiation time.

iii. Study the effect of corrosion inhibitors in

concrete, coating over concrete surface and use of

corrosion resistance steel in concrete on durability.

iv. Formulation of co-relation among durability

properties obtained from the study to determine the

service life estimation of Reinforced Cement

Concrete (RCC) structures induced by chloride

ingress.

v. Development of a software model using

MATLAB program to estimate the service life of

RCC structure induced by chloride ion.

An extensive literature survey has been made to

review the current knowledge on the service life

prediction of reinforced cement concrete structures

affected by chloride ions. Literature review also done

for the tests method followed by various researchers

to study the durability properties of concrete

structures and the method followed for service life

prediction.

The materials used in this study are Ordinary

Portland Cement (OPC), Portland Puzzolana Cement

(PPC), river sand and coarse aggregate, fly ash,

GGBS, superplasticizer, corrosion inhibitors and

water. The following concrete mixes were designed

and the details of mixes used in this study are as

follows;

 Control concretes; M25, M35, M40, M60 and

M75.

 Concrete with fly ash; M25 and M35 with

18%, 25% and 35% fly ash and M40, M60

and M75 with 30 % fly ash.

 Concrete with GGBS; M40, M60 and M75

with 40% GGBS.

 Concrete with Corrosion Inhibitors (CI) such

as Sodium Nitrite,

 Calcium Nitrate and Monoethanolammine;

M40 with 1, 2, 3 and 4%.

Test specimens of size 150 mm cubes were

prepared for determining the compressive strength,

and to measure water permeability and resistivity

values. Cylindrical specimens of size 100 mm dia.

and 200 high were prepared and sliced as 50 mm

thick after curing for RCPT and chloride diffusion

tests.

To study the effect of concrete cover thickness on

corrosion initiation time, high strength deformed bars

(TMT) of 8, 10, 16, 20 and 32 mm diameters were

used. Concrete cylinders of size 75 mm dia. 150 mm

height, 100 mm dia. 200 mm height and 150 mm dia.

300 mm height were used to have concrete cover

thickness of 29.5, 40, 46, 59 and 70 mm. The effect

concrete surface coating by using epoxy has been

studied by polarization study.

Co-relation of durability properties were

formulated with each other. The co-relation between

the durability properties gives an equation and helps

to estimate the service life of reinforced cement

concrete structures. Based on this, a software model

was developed using MATLAB program to predict

the service life. This model has been validated by

comparing the output obtained from the model with

the experimental results conducted in the laboratory.

2. Material and Methods Used

The materials used in the present study are

cement, fine aggregate, coarse aggregate, fly ash,

ground granulated blast furnace slag, super

plasticizer and water. In these, the cement used was

the commercially available 53-grade Ordinary

Portland Cement (IS: 12269-1987). The preliminary

test was done for the concrete ingredients as per the

respective standards. Table 3.1 presents the materials

tested for various parameters by appropriate test

method.

Table 1 Test carried out on Raw Materials

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e-I SSN: 2395-0463

Vol ume 02 I s s ue 9

September 2016

Available online: http://edupediapublications.org/journals/index.php/JSMaP/ P a g e | 154

The properties of cement are tabulated in Table 2.

The fine aggregate used was the river sand and the

coarse aggregate used was the crushed granite

aggregate conforming to IS-383-1970. The properties

of aggregates are given in Table 2. The class - F type

fly ash was obtained from Ennore thermal power

plant and Ground Granulated Blast Furnace Slag was

obtained from Vizag steel plant though Andhra

cements.

Table 2 Physical and Engineering Properties of Raw

Materials

The naphthalene-based superplasticizer was used

and the water used was the ordinary potable ground

water. The concrete mixes were designed as per IS- 10262-1982. The mix proportions are given based on

the total binder content (cement + mineral

admixture) and also water content has been given

based on the w/b ratio (binder = cement + mineral

admixture).

The following experiment studies have been

carried out to determine the mechanical and

durability characteristics of different grade of

concretes with and without mineral admixtures such

as fly ash and GGBS, chemical admixtures and

corrosion inhibitors. The durability properties studied

are as follows:

 Chloride Diffusion Values (Dc)

 Rapid Chloride Iron Penetration Test (RCPT)

 Concrete Resistivity (Rc)

 Water permeability (Wc)

 Accelerated Corrosion test (Lp)

3. Results and Discussion

Experiment were conducted to evaluate the

different durability properties of different types and

grades of concretes made with and without mineral

and chemical admixtures. The durability tests

conducted were of Rapid Chloride ion Penetration

Test (RCPT), Chloride diffusion, Water

Permeability, Resistivity and corrosion initiation

time, etc. ach durability parameter was co-related

with another parameter and for all the properties

were inter linked for estimating the service life of

Reinforced Cement Concrete (RCC) structures

induced particularly with chloride ions. The study

focused to estimate the service life of RCC structures

for a given durability property.

Durability properties such as RCPT and

diffusivity values were found to be decreased when

the strength of concrete increases. From the Fick’s

second law of diffusion, the corrosion initiation

period extended when the diffusivity of concrete

decreases. The polarization test results show that the

corrosion initiation period is directly proportional to

the concrete grade and cover thickness. The

corrosion initiation time has been enhanced for the

coated specimens. It was observed that the service

life of concrete structures against rebar corrosion

may be extended by using higher grade of concrete,

larger cover thickness and concrete surface coating.

In general, it was observed that when the RCPT

value was high, the chloride diffusion and water

permeability rates were also high. At the same time,

the concrete resistivity and corrosion initiation period

were less. Similarly, when the RCPT value was less,

the rate of chloride diffusion and water permeability

values were also less, and the concrete resistivity and

corrosion initiation period were high. The chloride

diffusion and water permeability values were directly

proportional to RCPT value. The concrete resistivity

and corrosion initiation time values were indirectly

proportional to RCPT value.