FRACTURE BEHAVIOUR OF CONCRETE WITH RICE ... - RJEAS

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Research Journal in Engi
neeri
ng and Applied Sciences 2(2
)
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Rjeas

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132


FRACTURE BEHAVIOUR OF CONCRETE WITH RICE HUSK ASH
REPLACEMENT UNDER UNIAXIAL COMPRESSIVE LOADING



Akinwonmi, Ademola Samuel
and
Seckley, Emmanuel

Department of Mechanical Engineering,

University of Mines and Technology,

Tarkwa, Ghana

Corresponding Author
:

Akinwonmi, Ademola Samuel

__________________________________________________________
__________
_______________
_______

RHA serves as partial replacement to cement in order to provide an economic use of the by product, reduce
RHA waste deposit and consequen
tly produce strong and durable concrete at a cheaper cost. This paper
therefore presents the fracture behaviour of concrete made from Ordinary Portland Cement with Rice
-
Husk Ash
(RHA) made from a rice paddy replacement up to the age of 28 days. Six differe
nt replacement percentages of
cement by RHA, (i.e. 0%, 10%, 15%, 20%, 25% and 30%) were used for the concrete specimens. The results
are compared with those of concrete without RHA (i.e. 0% RHA and 100% OPC). The weight was measured for
each sample specime
n for each RHA % level (0, 10, 15, 20, 25, and 30) and for the number of days for setting
of the concrete block cubes (7, 14, 21 and 28). Compressive test was carried out by applying a constant uniform
pressure through the testing machine on the cubes of t
he concrete blocks until failure occurs. Results show that
the more Rice Husk Ash used in the concrete mix, the lighter the finished concrete becomes, the higher the days
of setting of the concrete, the more the compressive force needed to break the block
, also, the higher the
replacement level of the Rice Husk Ash up to 30 %, the stronger the block. The significance of the study is that
RHA therefore provides a positive effect on the mechanical strength of concrete mix, up to 30 % Rice Husk Ash
replacemen
t up to the age of about 28 days and reduction in utilization of cement, and expenditures. Further
experiment should be performed to test the mechanical strength of concrete mix, beyond 30 % Rice Husk Ash
replacement above the age of about 28 days.




©Emerging Academy Resources



KEYWORDS
:

Mechanical Strength; Concrete; Cracks; Rice Husk Ash; Compressive test; Failure

________________
______________________________________________
____________________
__
______
INTRODUCTION

Cement, as a binder, is the most expensive input in to
the production of sand Crete blocks (Hornbostel,
1991). Ordinary Portland cement is acknowledged as
the major co
nstruction material throughout the world.
The production rate is approximately 2.1 billion
tons/year, and is expected to grow exponentially to
about 3.5 billion tons/year by 2015 (Coutinho, S. J.,
2003). From 1880 to 1996, the world’s annual
consumption of

Portland cement rose from 2 million
tons to 1.3 billion tons. This is associated with major
environmental issues which include: cement
manufacturing is the third largest CO
2

producer and
this accounts for over 50 % of all industrial CO
2

emissions (for eve
ry ton of cement produced, 1.25
ton of CO
2

is released to the air); 1600 ton of natural
resources are consumed to produce 1 ton of cement
(Muga, et al., 2005). This calls for the use of
sustainable binders. One of the most promising
materials is rice husk
ash (RHA).


According to
(Stroven et. al, 1999) the use of rice
husk ash in concrete was patent in the year 1924 up
to 1972, and (Deepa et. al, 2006) reported that all the
researches were concentrated to utilize ash derived
from uncontrolled combustion. (
Nehdi et. al, 2003) in
their experiment also concluded that controlled
combustion influence the surface area of RHA, so
that time, temperature and environment to be
considered to produce ash of maximum reactivity.


Rice husk is an agricultural residue fr
om the rice
milling process. The chemical composition of rice
husk vary due to the differences in the type of paddy,
type of fertilizer used, crop year, climate and
geographical conditions (Chandrasekhar, et al.,
2003). The husk of the rice is removed in t
he farming
process before it is sold and consumed. It has been
found beneficial to burn this rice husk in kilns to
make various things. The rice husk ash is then used
as a substitute or admixture in cement. Therefore the
entire rice product is used in an e
fficient and
environmentally friendly approach. The produced
partially burnt husk from the milling plants when
used as a fuel also contributes to pollution and efforts
are being made to overcome this environmental issue
by utilizing this material as a supp
lementary
cementing material (Chandrasekhar, et al., 2006).
Disposal of rice husk ash is an important issue in
these countries which cultivate large quantities of
rice. Rice husk has a very low nutritional value and
as they take very long to decompose are
not
Research Journal in Engineering and Applied Sciences

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Fracture Behaviour Of Concrete With Rice Husk Ash Replacement Under Uniaxial Compressive Loading


133


appropriate for composting or manure. Burning the
husk under controlled temperature below 800 °C can
produce ash with silica mainly in amorphous form
(Zhang, and Malhotra,1996)
.
The 100 million tons of
rice husk produced globally begins to impact the
e
nvironment if not disposed of properly. One
effective method used today to rid the planet of rice
husk is to use it to fuel kilns. Burning the rice husk is
an efficient way to dispose of the rice cultivation by
-
product while producing other useful goods. T
he rice
husk ash is a highly siliceous material that can be
used as an admixture in concrete if the rice husk is
burnt in a specific manner. The presence of mineral
admixtures in concrete is known to impart significant
improvements in workability and durab
ility. The
characteristics of the ash are dependent on the
components, temperature and time of burning (Chao,
et al., 2008). During the burning process, the carbon
content is burnt off and all that remains is the silica
content. The silica must be kept at
a non
-
crystalline
state in order to produce an ash with high pozzolanic
activity. The presence of silica in this pozzolanic
material makes possible the use of rice husk ash to
replace part of cement (Chandrasekhar, et al., 2003).
The ash, which has no usef
ul application, is usually
dumped directly in the environment and causes
pollution and air contamination. The rice husk
thereby constitutes an environmental nuisance as they
form refuse heaps in the areas where they are
disposed.


The objective of this wo
rk is therefore to investigate
into the mechanical strength of concrete by mixing
with rice husk ash since the use of these by
-
products
is an environmental
-
friendly method of disposal of
large quantities of materials that would otherwise
pollute the land,
water and air. And to serve as a
partial replacement to cement which will provide an
economic use of the by


product and consequently
produce strong and durable concrete at a cheaper
cost.


MATERIALS AND METHODS


Ordinary Portland® Cement (OPC) conforming

to
ASTM C 150 type I was used for this study, its
chemical and physical properties are given in Table
1.


Production Of The Block Samples Using Ordinary
Portland Cement
(OPC)

For the purpose of this work, 150 mm x 250 mm x
450 mm hollow blocks were produc
ed. The quantities
of materials obtained from the mix design were
measured using a weighing balance. The cement,
RHA and sand were then mixed together to obtain a
homogeneous mixture. Measured volume of water
was then poured on to the mixture using bucket.

A
shovel was used to mix the mixture to get the
required workability. A steel hollow mould was used
to mould the blocks. The block samples were cured
by sprinkling water every 12 hours.


Production of Rice Husk Ash

The rice husk used in this work husk was

collected
from paddy field in Ibadan, Nigeria. It was then burnt
in the laboratory by using a ferro
-
cement with
incinerating temperature of about 700°C. The ash was
collected and ground in a mill for about 180 minutes.
X
-
Ray Diffraction analysis was perfo
rmed to
determine the silica form of the produced Rice Husk
Ash (RHA) powder samples using an X
-
ray
diffractometer. Figures 1
-

4 show the pictures of
RHA before grinding, when burnt, after grinding and
under electroscope respectively.


Figure 1. Rice Husk

before grinding




Figure 2. Burnt Rice Husk




Figure 3. Rice Husk Ash after grinding


Research Journal in Engineering and Applied Sciences

(I
SSN: 2276
-
8467)

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2
):
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Fracture Behaviour Of Concrete With Rice Husk Ash Replacement Under Uniaxial Compressive Loading


134



Figure 4. RHA Particles under Electroscope


Table 1. Chemical Composition of the

Raw Material
Used

Material

OPC

RHA


SiO
2

(%)


20.99


88.32




Al
2
O
3
(%)



6.1
9



0.46




Fe
2
O
3

(%)



3.86



0.67





CaO (%)



65.96



0.67




MgO (%)



0.22



0.44




Na
2
O
3

(%)



0.17



0.12





K
2
O (%)


0.6


2.91

Specific gravity


2.95

2.11




Mix Proportions of Concrete Block Mixed With
Rice Husk Ash
(RHA)

In this wo
rk, six batches of concrete were produced
with varying amounts of Rice Husk Ash substituted
for Ordinary Portland Cement. There was a control
group with no rice husk ash i.e. 0 % replacement,
then followed by 10% replacement, 15%
replacement, 20% replaceme
nt, 25% replacement and
30% replacement. This is important because it fits the
conditions of rural and developing countries, where
cement is expensive and rice cultivation is
predominant.


COMPRESSION TEST

The compression tests for the concrete cubes were
carried out at the Fracture Mechanics Laboratory of
Mechanical Engineering Department, University of
Ibadan, Nigeria. Standard test procedures were used
for the experiment. Before the commencement of the
test, all specimens were weighed and the results
rec
orded and at the time of each respective test. The
weight was measured for each sample specimen for
each RHA % level (0, 10, 15, 20, 25, and 30) and for
the number of days for setting of the concrete block
cubes (7, 14. 21, 28). A constant uniform pressure

was applied by the testing machine to the cubes of the
concrete blocks until failure occurs. Cracks were
initially noticed on the specimen and the cracks
propagated until failure was finally observed when
the cube no longer could resist the force applied
to it
without breaking apart. Results of the experiment are
shown on table 2.


RESULTS AND DISCUSSION

TABLE 2.
Results of the Experiment


Batch Number

% of Rice Husk Ash

Date Produced

Date Tested

Age
(Days)


Mass

(g)

Compressive
Strength
(MPa)

1

0

1/07/2010

8/07/2010

7

7650

79.5

1

0

1/07/2010

15/07/2010

14

7520

82.4

1

0

1/07/2010

22/07/2010

21

7330

87.7

1

0

1/07/2010

29/07/2010

28

7200

90.7

2

10

1/07/2010

8/07/2010

7

7580

87.5

2

10

1/07/2010

15/07/2010

14

7480

90.2

2

10

1/07/2010

22
/07/2010

21

7370

95.4

2

10

1/07/2010

29/07/2010

28

7220

101.2

3

15

1/07/2010

8/07/2010

7

7500

95.2

3

15

1/07/2010

15/07/2010

14

7300

108

3

15

1/07/2010

22/07/2010

21

7240

115.2

3

15

1/07/2010

29/07/2010

28

7200

120.5

4

20

1/07/2010

8/07/2010

7

7440

1
10.2

4

20

1/07/2010

15/07/2010

14

7220

114

4

20

1/07/2010

22/07/2010

21

7170

118.5

4

20

1/07/2010

29/07/2010

28

7140

130

5

25

1/07/2010

8/07/2010

7

7200

120.4

5

25

1/07/2010

15/07/2010

14

7180

125.2

5

25

1/07/2010

22/07/2010

21

7140

128.2

5

25

1/07/
2010

29/07/2010

28

7080

138.4

6

30

1/07/2010

8/07/2010

7

7000

140.5

6

30

1/07/2010

15/07/2010

14

7100

143.4

6

30

1/07/2010

22/07/2010

21

7050

147.5

6

30

1/07/2010

29/07/2010

28

7010

155.8

Research Journal in Engineering and Applied Sciences

(I
SSN: 2276
-
8467)

2
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2
):
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32
-
1
36

Fracture Behaviour Of Concrete With Rice Husk Ash Replacement Under Uniaxial Compressive Loading


135




Figure 5. Graph of Mass of Concrete against Rice
Husk Ash %
.



Figure 5. Graph of Mass of Concrete against Ric
e
Husk Ash %



Figure 6. Graph of Compressive Strength against
Number of Days for setting


X
-
ray diffractometer analysis showed that the Rice
Husk Ash was mainly in amorphous form. And RHA
had higher su
rface area as shown figure 4. The results
in table 1 show that as the number of days for setting
increases, the mass of the concrete blocks decreases
for all batches of concrete. As the percentage of RHA
increases, the mass of concrete reduces and the
comp
ressive strength increases. This is also evident
in figure 5. Fig. 6 also revealed that as the number
of days increases, the compressive strength increases.
The compressive strength for the concrete having
30% RHA is higher than the compressive strength
of
concrete having 0% RHA.

CONCLUSION

The more Rice Husk Ash that is used in the mix, the
lighter the finished concrete becomes. Replacement
up to 30% of c
ement with Rice Husk Ash causes
reduction in utilization of cement, and expenditures,
also can improv
e quality of concrete at the age of
more than 28 days.


According to this study, addition of pozzolanic
materials like rice husk ash to the concrete, can
improve the mechanical strength of concrete. The
specimens with silica extracted from Rice Husk Ash
s
howed higher compressive strength values when
compared with their equivalent mixture without Rice
Husk Ash for up to 30% replacement and the age of
28 days.


ACKNOWLEDGEMENT

The authors are grateful to Prof. I. A. Adetunde,
Dean, Faculty of Engineering, Un
iversity of Mines
and Technology, Tarkwa for his valuable advice in
this work.


REFERENCES

Chao, C.Y.H., Kwong, P.C.W., Wang, J.H., Cheung,
C.W. and Kendall. G., 2008 “Co
-
firing coal with rice
husk and bamboo and the impact on particulate
matters and asso
ciated polycyclic aromatic
hydrocarbon emissions.” Bioresource Technology
(99)
,

pg 83
-
93.


Chandrasekhar S, Satyanarayana K, Pramada P and
Majeed J. 2006 “Effect of calcinations temperature
and heating rate on the optical properties and
reactivity of rice

husk ash”.
Journal of Materials
Science
(Norwell); 41(1): pg 7926
-
7933.


Chandrasekhar, S., Satyanarayana, K., Pramada, P.
N., Raghavan, P., 2003 “Review processing,
properties and applications of reactive silica from rice
husk”

an overview. Journal of Ma
terials Science,
38: pp. 3159


3168.


Coutinho, S. J., 2003 “The combined benefits of CPF
and RHA in improving the durability of concrete
structures”. cement and concrete composites: 25(1):
2003, pg 51

59.


Deepa G. N., Jagadish, K.S., Alex Fraaij, 2006,

Reactive pozzolanas from rice husk ash: An

alternative to cement for rural housing”, Cement and
Concrete Research 36: 1062
-
1071.


Hornbostel, C., 1991 “
Construction materials: types,
uses, and applications”
, John Wiley & Sons Inc.,
USA, pg. 271.


Muga,

H., Betz, K., Walker, J., Pranger, C., Vidor,
A., 2005 “Development of appropriate and
sustainable construction materials”, Sustainable
Futures Institute, pg. 17.

Research Journal in Engineering and Applied Sciences

(I
SSN: 2276
-
8467)

2
(
2
):
1
32
-
1
36

Fracture Behaviour Of Concrete With Rice Husk Ash Replacement Under Uniaxial Compressive Loading


136


Nehdi M., Duquette, J. El Damatty
, A
. 2003,
“Performance of rice husk ash produced using a

new
technology as a mineral admixture in concrete”,
Cement and Concrete Research 33: 1203


1210.


Stroven, P., Bui, D.D., Sabuni, E. 1999, “Ash of
vegetable waste used for economic production of low
to high strength hydraulic binders”, Fuel 78: 153

159.


Zhang, M. H and Malhotra, V. M. 1996

“High
performance concrete incorporating rice husk ash as a
supplementary cementing material.”
ACI Materials
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(Detroit)
;

93 (6): pg 629
-
636.