Effect of Thermal Cycles on Compressive Strength of Different ...

<strong>Effect</strong> <strong>of</strong> <strong>Thermal</strong> <strong>Cycles</strong> on Compressive Strength <strong>of</strong> Different
Grades <strong>of</strong> Concrete
K . Chandramouli 1 , P. Srinivasa Rao 2 , T. Seshadri Sekhar 3 , N. Pannirselvam 4 and P. Sravana 2
1 NRI Institute <strong>of</strong> Technology, Visadala, Guntur, Andhra Pradesh, 2 Jawaharlal Nehru Technological University, College <strong>of</strong>
Engineering, Hyderabad, Andhra Pradesh, 3 Principal Chirala Engineering College, Chirala, Prakasam District, Andhra Pradesh
4 Vellore Institute <strong>of</strong> Technology University, Vellore, Tamilnadu
ss.tirumala@gmail.com
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Abstract -- Concrete in structures when exposed to high Objectives <strong>of</strong> the Study: The objectives <strong>of</strong> the current research
temperature gets stressed. This paper reports on the work is to study the compressive strength <strong>of</strong> concrete for
experimental study on the compressive strength <strong>of</strong> ordinary different grades <strong>of</strong> M20, M30, M40 and M50 with zero
grade <strong>of</strong> concrete such as M20, M30, M40 and M50 subjected to
thermal cycles <strong>of</strong> 28, 56, 90, and 180 for 50° C.
thermal cycles at a temperature <strong>of</strong> 50º C. The experimental
program on concrete specimens <strong>of</strong> size 100 x 100 x 100 mm cubes
were cast for testing compressive strength. The test specimens
II. MATERIALS AND METHODS
were demoulded after 24 hours <strong>of</strong> air cooling and kept for water Cement: Ordinary Portland cement available in local market
curing for 28 days. The decrease in compressive strength <strong>of</strong> <strong>of</strong> standard brand was used in the investigation. Cement used
ordinary concrete mixes in comparison with zero thermal cycles has been tested for various proportions as per IS 4031-1988
for 50° C are observed to be varied from 14 to 23 % for 28, 56, and found to be confirming to various specifications are IS
90, and 180 thermal cycles.
12269-1987. The specific gravity was 2.96 and fineness was
3200 cm 2 /gm. The cement confirms to 53 Grade.
Keywords: Concrete, Grade <strong>of</strong> concrete, <strong>Thermal</strong> cycle.
I. INTRODUCTION
CONCRETE is an organic material than the high temperature
and its duration decreases the concrete strength and its
durability. Fire resistance <strong>of</strong> concrete is affected by factors
like temperatures, duration and condition <strong>of</strong> the fire. The type
<strong>of</strong> materials used in the construction has porosity and moisture
content <strong>of</strong> concrete, its thermal properties and the size <strong>of</strong>
structural member and the type <strong>of</strong> construction determines the
fire resistivity <strong>of</strong> the material and increase in the size <strong>of</strong>
structural member increase the fire resistance. To determine
the resistance <strong>of</strong> the concrete samples exposed to high
temperatures and in order to determine the compressive
strength <strong>of</strong> concrete at elevated temperatures. The unstressed,
property test method is to provide property data <strong>of</strong> concrete at
room temperature after exposed to elevated temperatures
[1, 2].
Coarse aggregate: Crushed angular granite metal <strong>of</strong> 20 mm
size from a local source was used as coarse aggregate. The
specific gravity <strong>of</strong> 2.61 and fineness modulus 7.13 was used.
Fine aggregate: River sand was used as fine aggregate. The
specific gravity <strong>of</strong> 2.58 and fineness modulus 3.25 .
Preparation <strong>of</strong> Specimens: The present investigation is a study
on the compressive strength <strong>of</strong> ordinary concrete specimens
subjected to thermal cycles at a temperature <strong>of</strong> 50º C. This
was planned to be carried out through an experimental
program on concrete specimens <strong>of</strong> size 100 x 100 x 100 mm
cubes for compressive strength. The test specimens were
demoulded after 24 hours <strong>of</strong> air cooling and kept for water
curing for 28 days. The design mix proportions are given in
Table 1.
At high temperatures, Portland cement concretes undergo
important changes in their properties, due to the degradation
<strong>of</strong> its internal structure. The concrete structures could be
exposed to high temperatures due to different reasons. Mainly
during exposure to fire; another one could be when the
structure or its elements are a part <strong>of</strong> industrial installations [3,
4]. The adverse effects <strong>of</strong> long-term exposure <strong>of</strong> plain cement
mortars and concrete to hot weather conditions [5].
<strong>Thermal</strong> Cycle Procedure: One thermal cycle constitute a
heating period <strong>of</strong> 8 hours and subsequent cooling (in air
room temperature) period <strong>of</strong> 16 hours. The standard
specimens after curing period were placed in electric
ovens at 50º C for 0, 28, 56, 90 and 180 thermal cycles.
The specimens were removed from ovens and then
allowed to cool in air for 2 hours after specified time.
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COMPRESSIVE STRENGTH OF CONCRETE
Then the specimens were tested for compressive strength
and the details are tabulated in Table 2.
III. RESULTS AND DISCUSSION
Compressive Strength <strong>of</strong> Ordinary Concrete at Zero <strong>Thermal</strong>
<strong>Cycles</strong>: Table 2 gives a comparative study on compressive
strength <strong>of</strong> various grades <strong>of</strong> ordinary concrete mixes <strong>of</strong> M20,
M30, M40 and M50 investigated at zero thermal cycles at 50º
C. The values are observed to be varied from 36.6 to 54.2
N/mm 2 .
Compressive Strength <strong>of</strong> Ordinary Concrete Mixes at 28
<strong>Thermal</strong> <strong>Cycles</strong>: Table 2 gives a comparative study on
compressive strength <strong>of</strong> various grades <strong>of</strong> ordinary concrete
mixes <strong>of</strong> M20, M30, M40 and M50 investigated at 28 thermal
cycles at 50º C. These values are observed to be varied from
31.1 to 46.1 N/mm 2 .
Compressive Strength <strong>of</strong> Ordinary Concrete Mixes at 56
<strong>Thermal</strong> <strong>Cycles</strong>: Table 2 gives a comparative study on
compressive strength <strong>of</strong> various grades <strong>of</strong> ordinary concrete
mixes <strong>of</strong> M20, M30, M40 and M50 investigated at 56 thermal
cycles at 50º C. The values are observed to be varied from
30.0 to 44.4 N/mm 2 .
Compressive Strength Properties <strong>of</strong> Ordinary Concrete Mixes
at 90 <strong>Thermal</strong> <strong>Cycles</strong>: Table 2 gives a comparative study on
compressive strength <strong>of</strong> various grades <strong>of</strong> ordinary concrete
mixes <strong>of</strong> M20, M30, M40 and M50 investigated at 90 thermal
cycles at 50º C. These values are observed to be varied from
28.9 to 42.8 N/mm 2 .
Compressive Strength <strong>of</strong> Ordinary Concrete Mixes at 180
<strong>Thermal</strong> <strong>Cycles</strong>: Table 2 gives a comparative study on
compressive strength on various grades <strong>of</strong> ordinary concrete
mixes <strong>of</strong> M20, M30, M40 and M50 investigated at 180
thermal cycles at 50º C. The values are observed to be varied
from 28.5 to 42.3 N/mm 2 . The variation <strong>of</strong> compressive
strength <strong>of</strong> ordinary concrete at 0, 28, 56, 90 and 180 thermal
cycles are presented in Fig.1.
Variation <strong>of</strong> the Compressive Strength <strong>of</strong> Ordinary Concrete
Mixes Compared With Zero <strong>Thermal</strong> <strong>Cycles</strong>: Table 3 gives
percentage decrease in compressive strength <strong>of</strong> various grades
<strong>of</strong> ordinary concrete mixes in comparison with zero thermal
cycles for 50° C is observed to be varied from 14 to 23 % for
28, 56, 90, and 180 thermal cycles.
TABLE 1 DESIGN MIX PROPORTIONS OF ORDINARY CONCRETE MIXES
Grade <strong>of</strong>
concrete
Cement
Fine
aggregate
Coarse
aggregate
w/c
M 20 1 2.30 3.52 0.55
M 30 1 1.96 3.25 0.50
M 40 1 1.51 2.93 0.40
M 50 1 1.31 2.54 0.36
TABLE 2 THERMAL EFFECTS ON COMPRESSIVE STRENGTH OF ORDINARY CONCRETE AT 50 ° C AT VARIOUS THERMAL CYCLES
Grade <strong>of</strong> concrete No <strong>of</strong> thermal
cycles
Compressive strength at 50 ° C
Compressive strength
(MPa)
M 20 M 30 M 40 M 50
0 36.6 41.5 47.9 54.2
28 31.1 35.3 40.7 46.1
56 30.0 34.0 39.3 44.4
90 28.9 32.8 37.8 42.8
TABLE 3
AT 50 ° C
PERCENTAGE OF VARIATION IN COMPRESSIVE STRENGTH OF ORDINARY CONCRETE COMPARED WITH ZERO THERMAL CYCLES
Grade <strong>of</strong> concrete
No. <strong>of</strong> thermal cycles
Compressive strength at 50 ° C
(Decrease)
M 20
0 -
28 15.02
56 18.03
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Compressive
Strewngtrh ( MPa)
M 30
M 40
M 50
90 21.03
180 22.13
0 -
28 14.94
56 18.07
90 20.96
180 21.93
0 -
28 15.03
56 17.95
90 21.08
180 21.92
0 -
28 14.94
56 18.08
90 20.80
180 21.96
Fig.1 Variation <strong>of</strong> Compressive Strength <strong>of</strong> Ordinary Concrete at Different
<strong>Thermal</strong> <strong>Cycles</strong> at 50º C
60
50
40
30
20
10
0
28 56 90 180
No <strong>of</strong> <strong>Thermal</strong> <strong>Cycles</strong>
M 20
M 30
M 40
M 50
IV. CONCLUSION
Concrete specimens containing ordinary Portland cement
undergo deterioration in term <strong>of</strong> compressive strength and
exposed to air temperatures higher than 25º C for a longer
period.
The effect <strong>of</strong> temperatures is related to either the weaker
formation <strong>of</strong> cement paste hydrates are the differential thermal
expansion <strong>of</strong> matrix components.
The decrease in compressive strength <strong>of</strong> ordinary concrete
mixes in comparison with zero thermal cycles for 50° C is
observed to be varied from 14 to 23 % for 28, 56, 90, and
180 thermal cycles.
V. REFERENCES
1. Phan LT, Carino NJ., 2003, Code Provisions for High
Strength Concrete Strength Temperature Relationship at
Elevated Temperatures, Material Structure, 36(256): 91–
98.
2. Husem M., 2006, The <strong>Effect</strong>s <strong>of</strong> High Temperature
on Compressive and Flexural Strengths <strong>of</strong> Ordinary and
High-Performance Concrete, Fire Safety Journal, 41:
155–63.
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COMPRESSIVE STRENGTH OF CONCRETE
3. Bazant, Z. and Kaplan, M., 1996, Concrete at High
Temperatures, Longman Group Limited, UK.
4. Smith, P., 1994, Resistance to Fire and High Temperature
Significance <strong>of</strong> Tests and Properties <strong>of</strong> Concrete and
Concrete-Making Materials, STP 169C, ASTM International,
West Conshohocken, PA, 282–295.
5. Mirza, W. H. & A1-Noury, S. I., 1985, Mortar in an
Adverse Climate, Concrete International Design and
Construction, ACI, 7 (8), 56-64.
Dr. Seshadri Sekhar.T graduated from KSRM
college <strong>of</strong> Engineering affiliated to S.V.
University, Tirupati in Civil Engineering, and
Completed M.Tech with specialization in
Structural Engineering from JNTU College <strong>of</strong>
Engineering Hyderabad.
Completed M.S.(S<strong>of</strong>tware Systems ) from BITS
Pilani. His research areas <strong>of</strong> interest are Special
Concretes. Has published over 60 research
papers.
He was associated with nearly 25 M. Tech projects. He is Member <strong>of</strong> ISTE,
IEEE and Fellow <strong>of</strong> IETE.
Dr P. Srinivasa Rao specialized in
structural engineering. His Research
interests are Concrete Technology,
Structural Design, High Performance
Concrete, Prefabricating Structures, Special
Concretes and use <strong>of</strong> Micro Silica, Fly Ash
in Building Materials. He has been
associated with a number <strong>of</strong> Design
projects, for number <strong>of</strong> organizations and
involved as a key person in Quality
control and Mix Designs.
Dr . P. Sravana is an Associate Pr<strong>of</strong>essor
at J.N.T.University , Kukatpally ,
Hyderabad. Specialized in transportation
engineering . Research interests are Special
concretes , Pavement Design. She has been
associated with a number <strong>of</strong> design
projects for number <strong>of</strong> organizations and
involved as a key person in Quality
control, Mix Designs and Bitumen
Evaluation Tests. .Has 12 years <strong>of</strong>
academic, research and industrial
experience and published over 30 research
papers.
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