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Effect of exposure time and elevated temperature on ordinary concrete

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Zhu J and Wu Y (2016) Effect of exposure time
and elevated temperature on ordinary concrete.
Emerging Materials Research,
http://dx.doi.org/10.1680/jemmr.16.00091

ice | science

Emerging Materials Research
Research Article
Received 20/04/2016
Accepted 12/12/2016
Keywords: material characterisation/mechanical properties/simulation

ICE Publishing: All rights reserved

Effect of exposure time and elevated
temperature on ordinary concrete
Jianing Zhu PhD

Yaopeng Wu PhD*

School of Civil Engineering, Xi’an University of Architecture and
Technology, Xi’an, People’s Republic of China

School of Civil Engineering, Xi’an University of Architecture and
Technology, Xi’an, People’s Republic of China

The concrete material in structures is likely to be exposed to elevated temperatures during fires. In this paper, an
experimental investigation is carried out to study the effect of different exposure temperatures and times on the
mechanical properties of ordinary concrete. Cylinders with a diameter of 100 mm and a height of 200 mm were used
as concrete specimens, which were tested at the three elevated temperatures of 200, 400 and 600°C for various


times from 1 to 6 h. It was found from the experimental results that the temperature of exposure is the main
contributor to the decrease in the weight and compressive strength of concrete and the exposure time has little
effect. Although the effect of exposure time on weight loss is greater at lower temperatures than that
at higher temperatures, after 3 h of exposure time, the difference becomes negligible. In addition, it was found
that the relative compressive strength of concrete remains unchanged for exposure times exceeding 3 h. The
numerical simulations were conducted using Abaqus. The predicted temperature distributions agree well with the
experimental results.

Notation
c
E
fc
fT
M0
MT
T
T0
t
l
r

1.

heat capacity
exposure time
initial compressive strength of the material at room
temperature
residual compressive strength of the material at elevated
temperature
weight of the specimen at room temperature

weight of the specimen at elevated temperature
exposure temperature
initial temperature
heating-up time
thermal conductivity
density

when it is exposed to different heating treatments with target
temperatures of 250, 500 and 750°C and a holding time of 2·5 h.
Demirel and Keleştemur,5 Akca and Zihnioğlu,6 Tanyildizi7 and
Bastami et al.8 investigated the properties of concrete subjected to
high temperatures with exposure time of 1 h. Moreover,
Kizilkanat et al.,9 Lo Monte and Gambarova10 and Rashad11
investigated the performance of concrete by using a heating
method with an exposure time of 2 h. A standard exposure time of
3 h has been used by many researchers.12–19 In addition, both
heating parameters of the peak temperature and the exposure time
were simultaneously considered. For example, peak temperatures
of 400, 500, 550 and 600°C and exposure times of 0, 1 and 2 h
were used in the experiment by Yang et al.,20 and specimens were
exposed to temperatures of 100 and 200°C for a period of 1, 2 or
3 h by Al-Salloum et al.21

Introduction

Fire is one of the biggest threats to buildings. Since concrete has
become a primary construction material, studies on the material
properties of concrete after exposure to elevated temperatures
have gained great attention. Many studies were carried out on the
influence on the properties of concrete on heating rate, exposure

temperature, exposure time and so on.1,2
3

Ergün et al. assessed the effects of elevated temperatures and
cement dosages on the mechanical properties of concrete. In their
tests, six-test series were conducted with each series consisting of
six different temperatures of 20, 100, 200, 400, 600 and 800°C.
The samples tested at 20°C were considered the baseline
specimens. Once the targeted temperature was reached, this
temperature was maintained for 45 min to achieve a thermal
steady state. Biolzi et al.4 described the consequences of
progressive damage in architectural high-performance concrete

In this 102
+5·986 × 102
+5·984 × 102
+5·982 × 102
+5·981 × 102
+5·979 × 102
+5·977 × 102
(b)

(a)
NT11

NT11
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102

+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102

+6·000 × 102
+6·000 × 102
+6·000 × 102
+5·999 × 102
+5·999 × 102
+5·999 × 102
+5·999 × 102
+5·999 × 102
+5·998 × 102
+5·998 × 102
+5·998 × 102
+5·998 × 102
+5·998 × 102
(c)
NT11

(d)
NT11

+6·000 × 102

+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102

+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
+6·000 × 102
(f)

(e)


Figure 4. Temperature distributions after exposure at 600°C for (a) 1, (b) 2, (c) 3, (d) 4, (e) 5 and (f) 6 h

600°C. As the exposure time is increased from 1 to 3 h, the
weight ratio decreases at each exposure temperature. After over
3 h of exposure time, however, the weight ratio is kept at a
relatively constant value, indicating no further weight loss.
Furthermore, the effect of exposure time on weight loss is greater
at lower heating temperatures (such as 200°C) than that at higher
heating temperatures (such as 600°C).
The results in Figure 5 demonstrate that the weight loss of the
concrete specimen occurs mainly at the early stage of hightemperature exposure and almost no further weight loss occurs
after 3 h of exposure. Therefore, 3 h of exposure time at an
elevated temperature is sufficient in the study of the effect of the
temperature effect on the behaviour of the ordinary concrete.
4

4.2 Compressive strength
Shown in Figure 6 are the relative compressive strengths of concrete
after the specimen was subjected to different exposure temperatures
with different exposure times, in which the data are the average data
from three replicate tests. The relative strength is defined as the ratio
of the residual compressive strength at the elevated temperature to
the initial compressive strength at room temperature. It can be
concluded from Figure 6 that the decrease in the compressive
strength of the specimen results mainly from the exposure
temperature and the exposure time has no significant effect on the
residual strength in the specimen. It is also seen from Figure 6 that
at an exposure temperature of 200°C, the relative compressive
strength of concrete decreases only slightly when compared to the
original strength and is almost independent of the exposure time.


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Emerging Materials Research

Effect of exposure time and elevated
temperature on ordinary concrete
Zhu and Wu

1·00

1·10

0·99

200ºC

0·98

400ºC

1·00

600ºC

0·90
0·80

0·96

0·95

fT/fc

MT/M0

0·97

0·94

0·60

0·93
0·92

0·50

0·91

0·40

0·90

1

2

3
4
Exposure time: h


5

0·30

6

Figure 5. Relation of the weight ratio of the specimen with the
exposure time at different exposure temperatures

When the exposure temperature rises to 400 and 600°C, the relative
compressive strength of concrete decreases significantly as the
exposure temperature increases, and at 600°C less than 60% of the
original compressive strength is maintained. At high exposure
temperatures of 400 and 600°C, the relative compressive strength
of concrete slightly decreases as the exposure time is increased
from 1 to 3 h and then is almost independent of exposure time after
3 h. This implies that exposure time exceeding 3 h cannot further
change the relative compressive strength of concrete.

5.

0·70

Conclusions

The influence of the exposure temperature (200, 400, 600°C) and
the exposure time (1–6 h) on the weight loss and the relative
compressive strength of concrete was investigated in this study.
Based on this experimental study and the numerical simulation

using Abaqus, the following conclusions can be made.
■ The decrease in the weight and compressive strength of

concrete results mainly from the exposure temperature, and
effect of the exposure time is insignificant.
■ The effect of the exposure time on weight loss is greater at a
lower exposure temperature (200°C) than that at a higher
temperature (600°C).
■ No further weight loss and decrease in the relative compressive
strength of concrete occur after 3 h of exposure time.
■ Three hours of exposure time is sufficient to reach a stable
state for ordinary concrete at elevated temperatures, which is
further confirmed by numerical simulation results using
Abaqus.

1

2

400ºC
3
4
Exposure time: h

600ºC
5

6

Figure 6. Relation of the compressive strength of the specimen

with the exposure time at different exposure temperatures

Government of China (CXY1432(4)), Opening Funds of State
Key Laboratory of Building Safety and Built Environment
(BSBE2016-2) and Innovation Team of Xi’an University of
Architecture and Technology. The authors are grateful to the
financial support provided by all sponsors.
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Acknowledgements
This research was sponsored by the National Natural Science
Foundation of China (51108371), Shaanxi Natural Sciences

Foundation of China (2015JM5164), Key Laboratory of
Education Department of Shaanxi Provincial Government of
China (16JS050), Xi’an Foundation of Shaanxi Provincial

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11.

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