ANTI CORROSIVE ACTIVITY OF FLY ASH BLENDED ...€¢ Lower percentage of C3A resulting in low heat of...

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International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 8, August 2017, pp. 637–648, Article ID: IJCIET_08_08_065

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ISSN Print: 0976-6308 and ISSN Online: 0976-6316

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ANTI CORROSIVE ACTIVITY OF FLY ASH

BLENDED CEMENT CONCRETES

Ch. Chandramouli

Civil Engineering Department, AITAM, Tekkali, Andhra Pradesh, India

S. Ramlal


B.Govinda Rajulu


ABSTRACT

Concrete occupies a unique position among modern construction materials. It is

the only material manufactured at construction sites. It gives considerable freedom to

the architect to mould the structural element to any shape or form a freedom that is

not possible with other materials. Of course, concrete has limitations it cannot on its

own flow past obstructions into nooks and crannies. Though compaction, often using

vibration, is essential for achieving strength and durability of concrete. As concrete is

produced and placed at construction sites, under conditions far from ideal, we do

often end up with pleasant results rock pockets, sand streaks and a host of

workmanship related problems.

Fly ash blended concrete has evolved as an innovative technology, capable of

achieving the status of being an outstanding advancement in the sphere of concrete

technology. As so many construction companies are using the fly ash in their projects,

this boomed in every mind to what extent the fly ash can be used and so research is

going on this. The utilization of fly ash will reduce the dumping of fly ash as well as

decrease the construction cost also.

In reality many of the concrete structures exposed to sever environmental

condition exposed to sea water in case of marine structures and sever aggressive

conditions in case of fertilizer industry where the durability of concrete structure is

important. In this aspect our project is aimed to test the fly ash blended concrete in

corrosion and the same concrete cubes were tested for compressive strengths cured in

different chemicals and this is compared with normal curing.

Key words: Fly ash, Fly ash blended concrete, Durability of Concrete, Compressive

Strength.

Ch. Chandramouli, S. Ramlal and B.Govinda Rajulu


Cite this Article: Ch. Chandramouli, S. Ramlal and B.Govinda Rajulu, Anti

Corrosive Activity of Fly Ash Blended Cement Concretes, International Journal of

Civil Engineering and Technology, 8(8), 2017, pp. 637–648.

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=8

1. INTRODUCTION

One of the major problems of durability of reinforced concrete is the rebar corrosion. Rebar

corrosion occurs when the concrete fails to give adequate protection to the embedded steel.

The problem gets compounded since the rebar corrosion damages the surrounding concrete

during the process of corrosion reaction. It is a common opinion that rebar corrosion takes

place mainly because of the failure of concrete to protect if from aggressive environment. The

protection methods include, coating of steel, larger cover thickness, better quality concrete,

corrosion inhibitors, and catholic protection.

Portland cement concrete has been the construction material par excellence for decades

for its mechanical strength and cost effectiveness, not to mention its properties in general that

make it particularly well suited to building. Nonetheless, the destruction of natural quarries

entailed in obtaining the prime materials involved, the energy intensity of Portland cement

manufacture and the environmental impact of gas emissions (essentially Co2 and Nox), etc.,

have prompted a search for alternative materials. Moreover, the use of conventional concrete

is notoriously subject to durability issues, foremost among which are the problems generated

by curing at high temperatures (construction during the summer months, thermal treatment

during precasting, etc.,) or expansive reactions (aggregate – alkali reaction, formation of

thaumasite, etc.). etc.

The service life of a reinforced concrete member with regard to corrosion can be modeled

in a simple way as shown in fig.1. This model consists essentially two parts – one the

“Initiation period” and the other the “propagation period”.

Initiation period is influenced by the quality and thickness of cover concrete. The main

parameter that qualifies the cover of concrete is the diffusion characteristic with regard to

chloride ion. An accelerated laboratory test method developed at SERC where the concrete

specimen containing rebar is subjected to polarization under a constant voltage in a sodium

chloride solution. Using this method many specimens were evaluated for its corrosion

resistance under two grades of concrete.

2. EXPERIMENTAL PROGRAMME

To increase the quality of concrete, cement is the main parameter in terms of strength and

resistance. The experimental programme was divided into the following three phases.

• Identification of best cement

• Fly ash

• Tests on hardened concrete

2.1. Cement

In a first approach Grade 53 cements of different brands (namely C-1, C-11, C-111, C-IV and

C-V) were tested as per IS: 4031-1968. The strength development was slightly lower as even

required by IS: 12269-1987. Beside compressive strength the hardening behavior and speed

were investigated by measuring the heat development of a cement paste in a thermos

container, which enabled semi-adiabatic conditions.

Anti Corrosive Activity of Fly Ash Blended Cement Concretes


For the test a cement paste consisting of 200gms cement and 70ml water was mixed in a

plastic beaker. Immediately after mixing, the beaker was placed in a thermos container and

equipped with a thermo-wire. The temperature gain was recorded over about 22hrs.

The only alternative to a grade 53 was special cement, which is used for the production of

prestressed concrete elements (Railway sleepers) because of its high and consistent quality.

The special cement of different brands was represented as SC-I and SC-II.

The one day compressive strength of special cement was 20-25Mpa which is considerably

higher than tested for the common grade 53 cements and matched at 7days. The BIS

requirements are greater than 27Mpa with 28-30 Mpa.

2.1.1. Physical Properties of Sleeper Cement

Tests are carried out as per IS: 4031-1968)

Normal Consistency – 29.5%

1. Specific Gravity – 3.15

2. Setting time (a) initial – 130 min

(b)final – 220 min

3. Fineness - 3700 gm/mm² Blains

Note: Finally the best one even from the special cements is selected from the temperature

curves for the investigated cements.

2.1.2. Advantages of Sleeper Cement

• Its negligible chloride content protects against corrosion.

• High fineness enhances workability with proper water cement ratio, ensuring water

cement ratio, density, and compactness, smooth, waterproofed and durable concrete.

• Lower percentage of C3A resulting in low heat of hydration, reduces cracks and hence

leading to greater durability.

2.2. Aggregates

Locally available river sand of specific gravity 2.53 with fineness modulus of 2.91

conforming to zone II. The fines content in river sand affects the performance of SPs and

crushed quarried granite stones of specific gravity 3.01 for 20mm aggregate and 2.96 of

10mm aggregate were used as fine and coarse aggregates respectively in all concrete mixes

throughout the investigation.

SIEVE ANALYSIS OF FINE AGGREGATES

Sieve Size

in mm

Weight of sand

retained on each

sieve (grams)

Cumulative

Weight retained

(grams)

% Cumulative

weight retained

(ΣF)

% cumulative

weight passing

4.75 0 0 0 0

2.36 2 2 1 99

1.18 11 13 6.5 93.5

0.6 26 39 19.5 80.5

0.3 83 122 61 39

0.15 62 184 92 8

PAN 14 198 99 1

Table 1 Sieve Analysis of Fine Aggregates



Figure 1 Sieve Analysis of Fine Aggregates

SIEVE ANALYSIS OF COARSE AGGREGATES

For 10 mm size Aggregates

Sieve Size

in mm

Weight of sand

retained on each

sieve (grams)

Cumulative

Weight retained

(grams)

% Cumulative

weight retained

(ΣF)

% cumulative

weight passing

20 0 0 0 100

10 114 114 5.7 94.3

4.75 1886 2000 100 0

2.36 0 0 0 0

PAN 0 0 0 0

Table 2 Sieve Analysis of Coarse Aggregates for 10 mm size Aggregates

Figure 2 Sieve Analysis of Coarse Aggregates for 10 mm size Aggregates

We

igh

t o

f S

an

d R

eta

ine

d

Sieve Size

SIEVE ANALYSIS OF FINE AGGREGATES

% cumulative weight

passing

% Cumulative weight

retained (ΣF)

Cumulative Weight

retained (grams)

Weight of sand retained

on each sieve (gms)

We

igh

t R

eta

ine

d

Sieve Sizes

SIEVE ANALYSIS OF COARSE AGGREGATES for

10 mm Size Aggregates

% cumulative weight

passing

% Cumulative weight

retained (ΣF)

Cumulative Weight

retained (grams)

Weight of sand retained

on each sieve (gms)



SIEVE ANALYSIS OF COARSE AGGREGATES

For 20 mm size Aggregates

Sieve Size

in mm

Weight of sand

retained on each

sieve (grams)

Cumulative

Weight retained

(grams)

% Cumulative

weight retained

(ΣF)

% cumulative

weight passing

25 0 0 0 100

20 404 404 20.2 79.8

10 1596 2000 100 0

4.36 0 0 0 0

PAN 0 0 0 0

Table 3 Sieve Analysis of Coarse Aggregates for 20 mm size Aggregates

Figure 3 Sieve Analysis of Coarse Aggregates for 20 mm size Aggregates

2.3. Fly ash

Fly ash from the nearby thermal power plant was collected and was replaced with the cement

at the time of making the concrete in different percentage of replacements.

Fly ash is the most widely used pozzolanic material all over the world. Fly ash has almost

become a common ingredient in concrete, particularly for making high strength and high

performance concrete. In INDIA fly ash was used in s’RIHAND dam construction replacing

cement up to 15%.

One of the important characteristics of fly ash is the spherical form of the particles this

shape of particles improves the flow ability and reduces the water demand.

We

igh

t R

eta

ine

d

Sieve Size

SIEVE ANALYSIS OF COARSE AGGREGATES for 20 mm Size

Aggregates

% cumulative weight passing

% Cumulative weight retained

(ΣF)

Cumulative Weight retained

(grams)

Weight of sand retained on

each sieve (gms)



2.3.1. Advantages of Fly Ash:

• Lower the heat of hydration and thermal shrinkage

• Increases the water tightness

• Reduces the alkali aggregate reaction

• Improves the resistance to attack by sulphates soils and sea water

• Improves extensibility

• Lowers susceptibility to dissolution and leaching

• Improves workability

• Lowers the cost

3. EXPERIMENTAL PROCEDURE

The performance of different steel bars kept under different grades of blended concretes was

assessed in the laboratory for its corrosion resistance property using the accelerated corrosion

test method.

The experimental set up essentially consists of a non-metallic container, in which water

mixed with 3.5% NaCl solution is to be poured to the required level. In this container, the

cylindrical concrete specimen with rebar is to be placed centrally and around this a stainless

steel plate is kept. The rebar of the concrete cylinder is connected through an electrical lead to

a D.C. Power supply to the anode terminal (+ Ve) and the stainless steel plate to the cathode

terminal (- Ve). This set up forms an electrochemical cell with rebar acting as anode and

stainless steel plate as cathode. Fig.2 shows a schematic view of polarization test setup.

Number of such cells can be made and connected to a D.C. power pack of multichannel

system. A constant voltage of about 3.0 V was applied from the D.C. Power pack.

Since chloride ions are negative ions, these will be attracted towards rebar which is

serving as anode by migration through the concrete. For this applied voltage, there will be

current response which can be measured using an ammeter and the current response will

depend on the total resistance of the cell system. This applied voltage was kept constant and

as the time increases, the chloride migration will increase and once sufficient chloride, equal

to the critical chloride content for the type of steel rebar used reaches the steel surface,

depassivation will occur and this will get reflected in a sudden increase in the current

response. As the experiment continues, the current will increase indicating the activity of

corrosion. This phenomenon will be distinctly predominant in the specimens with high % of

fly ash replacement of concrete specimens.

On the other hand, the concrete specimens with replacement of fly ash will have high

resistance and initially the current response will be considerably low.

As the time goes, the current may increase only slightly and will remain fairly constant at

a low level depending on the dosage of fly ash content.

This is an indication that the dosage of fly ash increases the migration of chloride ions

even under an externally applied electrical field. It is generally experienced that the

polarization test will normally require a period of 40 – 50 days by which time the rebar

embedded in blended concrete specimens would undergo sufficient corrosion.

On completion of the polarization test, the concrete cylinders were taken out and the

weight loss of the rebar was determined. As this test simulates a real condition of a structure

exposed to marine environment, the test results can be considered meaningful for a

performance evaluation with regard to controlling corrosion.



Figure 4 polarization Set up

Figure 5 Details of Concrete Test Specimen

4. MIX DESIGN

Present work of the studies was carried out for grade of concrete M25 the mix design can be

carried out according to the IS 10262:1982.

Mix proportions as follows:

Water in

ltrs Cement in kgs

Fine aggregate in

kgs Coarse aggregate in kgs

191.58 383.16 572.10 1282.16

0.5 1 1.49 3.35

Table 4 M25 Grade Concrete Mix proportions.



5. ANALYSIS OF RESULTS

COMPRESSIVE STRENGTHS OF M25 GRADE HARDENED CONCRETE IN NORMAL WATER

Sl.No Curing

Condition Description 7 days 28 days 90 days

1 Normal water

Conventional Concrete 16.3 26.67 26.74

10% replacement of Fly ash 12.11 24.63 26.8




Table 5 M25 Grade Concrete Compressive Strengths of replacement of fly ash in Normal Water

Figure 6 M25 Grade Concrete Compressive Strengths of replacement of fly ash in Normal water

COMPRESSIVE STRENGTHS OF M25 GRADE HARDENED CONCRETE IN SEA WATER

Sl.No Curing Condition Description 7 days 28 days 90 days

1 Sea water

Conventional Concrete 14.5 24.22 26

10% replacement of Fly ash 11.2 24.22 26




Table 6 M25 Grade Concrete Compressive Strengths of replacement of fly ash in Sea Water

Com

pre

ssiv

e S

tren

gth

s in

Mp

a

Replacement of Fly Ash

COMPRESSIVE STRENGTHS OF M25 GRADE

HARDENED CONCRETE IN NORMAL WATER

7 days

28 days

90 days



Figure 7 M25 Grade Concrete Compressive Strengths of replacement of fly ash in Sea water

COMPARISION OF COMPRESSIVE STRENGTHS OF M25 GRADE CONCRETE IN NORMAL & SEA

WATER

7 days 28 days 90 days

Normal

water

Sea

water

Normal

water

Sea

water

Normal

water

Sea

water

Conventional Concrete 16.3 14.5 26.67 24.22 26.74 26

10% replacement of Fly ash 12.11 11.2 24.63 24.22 26.8 26

20% replacement of Fly ash 9.16 8.26 25.71 25.13 26.92 26.23



Table 7 Comparison of Compressive Strengths of M25 Grade Concrete in Normal & Seawater

Figure 8 Comparison of Compressive Strengths of M25 Grade Concrete in Normal & Seawater

Com

pre

ssiv

e st

ren

gth

s in

Mp

a

Replacement of Fly Ash

COMPRESSIVE STRENGTHS OF M25 GRADE

HARDENED CONCRETE IN SEA WATER

7 days

28 days

90 days

Com

pre

ssiv

e sr

ength

s in

Mp

a

Duration

COMPARISION OF COMPRESSIVE STRENGTHS OF M25

GRADE CONCRETE IN NORMAL WATER & SEA WATER

Conventional Concrete

10% replacement of

Flyash

20% replacement of

Flyash

30% replacement of

Flyash

40% replacement of

Flyash



CURRENT VALUES IN mA

Time in

Days

Conventional

Concrete

10% Flyash

Replacement

20% Flyash

Replacement

30% Flyash

Replacement

40% Flyash

Replacement

1 2 2.9 3.3 4.1 3.7

3 2 2.9 3.3 4.1 3.7

4 2 2.9 3.3 4.1 3.7

5 2 2.9 3.3 4.1 3.7

7 2 2.9 3.3 4.1 3.7

9 2 2.9 3.3 4.1 3.7

12 3 2.9 3.3 4.1 3.7

15 4 3.4 3.3 4.1 3.7

17 4.5 3.4 3.9 4.1 3.7

23 5 4.6 5.6 4.1 4.3

27 9 5.3 7.7 4.1 5.8

30 9 8.1 7.7 4.1 7.3

33 9 8.1 7.7 4.1 7.3

38 9 8.1 7.7 4.1 7.3

42 9 8.1 7.7 4.1 7.3

45 9 8.1 7.7 4.1 7.3

47 9 8.1 7.7 4.1 7.3

49 9 8.1 7.7 4.1 7.3

52 9 8.1 7.7 4.1 7.3

56 9 8.1 7.7 4.8 7.3

59 9 8.1 7.7 4.8 7.3

63 9 8.1 7.7 4.8 7.3

65 9 8.1 7.7 4.8 7.3

68 9 8.1 7.7 4.8 7.3

70 9 8.1 7.7 4.8 7.3

Table 8 Comparison various % of Fly ash Replacement with Current values in mA

Figure 9 Comparison various % of Fly ash Replacement with Current values in mA

Cu

rren

t in

mA

Time in Days

Comparision Various % of Flyash Replacement with Current Values in mA

CURRENT VALUES IN mA

Conventional Concrete

CURRENT VALUES IN mA 10%

Flyash Replacement


Flyash Replacement


Flyash Replacement


Flyash Replacement



6. CONCLUSIONS

The following conclusions made from the results of compressive strengths and from the

analysis of graphs

1. From the results obtained and graphs represents that increase in the percentage of

replacement of fly ash is a grade of concrete, the initiation time of corrosion is

increases. The initiation time is also increases with increase in a grade of concrete.

2. From the results obtained and graphs represents that the controlled concrete the

initiation time of corrosion starts at the age of 10 days.

3. From the results obtained and graphs represents that the fly ash blended concrete the

initiation time of corrosion starts at the age of 52 days for M25 grade concrete 30%

replacement of fly ash.

4. From the observations as the percentage of fly ash replaced increases then the

compressive strengths decreases at the initial days. It is clearly observed that the

controlled concrete gives higher strengths than the fly ash blended concrete in normal

curing in the initial days (up to 28 days). Whereas the compressive strength is more in

fly ash blended concrete at 90 days.

5. For longer duration, 0 to 30% replacement of fly ash blended concrete gives higher

compressive strength in sea water curing but 40% replacement gives lesser strength.

7. FURTHER SCOPE OF STUDY

• The grade of cement used in the present study is IRST-40. The study can be further

investigation with 43 and 33 grades of ordinary Portland cement.

• In the present study HT fly ash of field-3 is used. This can be further investigation

with HT fly ash of different field.

• In the present study M25 grade concrete is considered. This can be further

investigation with other cements and other grades of concrete also.

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Issue 6, June (2014), pp. 99-107

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