International Journal of Applied Engineering Research ISSN 0973-4562 Volume 11, Number 9 (2016) pp 6753-6756
© Research India Publications. http://www.ripublication.com
Effect of thickness on impact resistance of lightweight aggregate concrete
Javad Yahaghi1, a, Nur Liyana Binti Mohd Kamal1, b, Zakaria Che Muda1, c, Payam Shafigh2, d, and Salmia Binti Beddu1, e
1
Department of Civil Engineering, Faculty of Engineering, Universiti Tenaga Nasional,
Jalan IKRAM-UNITEN, 43000 Kajang, Selangor, Malaysia
2
Department of Building Surveying, Faculty of Built Environment, University of Malaya, 50603 Kuala Lumpur, Malaysia
repeated blows and absorb energy without adverse effect to
cracking and spalling [7].Impact scenario can also be
classified into low velocity impact and high velocity impact.
The majority of the instrumented experimental research were
done using drop weight system to achieve high energy level at
a low impact velocity using large drop mass [8]. These low
velocities which falls within the range of few meters is
preferred due to the ease in using the instrument compared to
tests which employs high velocity.
Impact resistance of oil palm shells lightweight concrete slab
with bamboo fibers has been studied and the results indicate
that 2% volume fraction of bamboo fibers has an optimal
performance for first crack resistance and ultimate crack
resistance [1]. The effect of various amount geogrid content
on the impact resistance of the OPS reinforced concrete slab
of 20 mm thick also studied [9]. A low velocity impact test [8]
shows that steel fiber improve the impact resistance of
concrete slab better than other type of fibers. Another study on
concrete slab with recycled coarse aggregate[10] shows that
concrete made of 50% and 100% recycled aggregate generates
more strain energy compared to the ordinary concrete.
The objectives of the research reported in this paper are aimed
at determine the impact and crack resistance of OPS
lightweight concrete slabs with different thickness.
Abstract
This paper explore the impact resistance of lightweight
aggregate concrete from the results of an experimental study.
The lightweight aggregate used in this study was oil palm
shell, which is an agricultural solid waste, origin from palm
oil industry. Oil palm shell (OPS) is a main solid pollutant of
the environment and can be used as a replacement for the
conventional aggregate in lightweight concrete. A selffabricated drop-weight impact test rig was used to simulate a
low-velocity projectile impact on the slab specimens.
Different thickness of 20, 30 and 40 mm were tested for
impact resistance on specimens. The outcome demonstrate
that increasing the thickness improves the impact resistance
significantly, but the effect is more pronounced for ultimate
failure crack resistance than the first crack resistance.
Keywords: Lightweight aggregate concrete; Oil palm shell;
Impact resistance; Thickness
Introduction
Due to the increasing cost of raw materials and the continuous
reduction of natural resources development of lightweight
concrete by use of waste material become very important
subject for research in construction industry. Waste materials,
when properly processed, have shown to be effective as
construction materials and readily meet the design
specifications[1]. Both natural and artificial aggregates are
used in the construction industry. Expanded clay and sintered
pulverized fuel ash aggregates used in lightweight concrete
are well known, but these artificial aggregates are limited in
supply[2]. Oil palm shell (OPS) as one of the main agriculture
wastes has been researched on to replace aggregate in
lightweight concrete. Oil palm shell which has a density much
lower than the normal aggregate contributes to the lightweight
characteristic of the lightweight concrete. When researches
had been resumed to increase the strength of OPS lightweight
concrete to create mix design with high strength, it became an
ideal alternative as the major construction material.
Comparing the OPS concrete with other light weight
aggregate concrete and normal weight concrete in previews
studies shows a well performance in terms of structural
behaviour including bond, ductility and shear resistance[3-6].
However, due to the problems surfaced such as low flexural
strength, it was prevented to be used in concreting purposes,
especially in structures concreting such as slab or beam.
Understanding of concrete under dynamic loading is
important in designing certain type of buildings. Impact
resistance represents the ability of concrete to withstand
Experimental details
Materials.
The materials used in this study were ASTM type I ordinary
Portland cement; local mining sand, OPS in a saturated
surface dry condition, with a maximum size of 12.5 mm,
specific gravity, compacted bulk density and 24 h water
absorption of 1.22, 673 kg/m3, and 21%, respectively, was
used as lightweight aggregate. The Super plasticizer(SP) used
in this study was Sika ViscoCrete-15RM, supplied from Sika,
is in conformity with EN 934-2.
Mix proportions.
The mix design used in this study are shown in Table 1.
Table 1: Mix proportions of concretes in a batch
Mix
code
L
6753
Cement
(kg)
32.70
Water
(kg)
11.14
Sand
(kg)
55.00
Granite
(kg)
24.20
OPS
(kg)
16.30
SP
(%)
1
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 11, Number 9 (2016) pp 6753-6756
© Research India Publications. http://www.ripublication.com
Test methods.
All materials except water and SP were put into a mixer and
mixed for 3 min; 70% of the mixing water together with SP
was added and mixed for 5 min, then, the remaining water
was added and mixed for another 10 minutes. Before casting
the samples, the slump test of the mixture was performed. The
concrete specimens were cast in steel molds and compacted
on a vibration table. For this mixture, 18 cubes (100×100×100
mm) were used for the measuring of compressive strength at
1, 3, 7 and 28 days, oven dry density and impact resistance,
respectively. The specimens were demolded one day after
casting. After 28 days 3 cubs from each mixture cut to 20, 30
and 40 mm thickness for impact test. As can be seen in Figure
1 the impact test used in this study was low velocity dropweight impact test using two type of steel ball weighting
0.380 kg and 1.25 kg with drop height of 360 mm impacting
the specimen of size 100 × 100 mm with thickness of 20, 30
and 40 mm mounted on the frame. At the first crack and
ultimate (failure) crack, the total crack length, the crack width
and the crack depth measured with its total numbers of blows
recorded.
In the research reported in this paper, the crack width and the
crack length are measured using feeler gauge and ruler while
the crack depth was assumed to be same as the thickness of
specimens. The crack resistance is due to the inconsistent
crack depth developed along the crack length. The ultimate
crack resistance Ru is calculated as following formula [11];
N×e = Ru× lc× dc× wc.
(1)
Where, N = No. of Blows, e = Energy per blow (Joules), lc =
Total length of all cracks, dc = Maximum crack depth, wc =
Maximum crack width, Ru = Ultimate crack resistance.
Another dimensionless factor impact crack resistance ratio
was also defined:
Cr = Ru / fcu .
(2)
Where, Cr = Impact crack resistance ratio, fcu = cube
compressive strength of the concrete slab.
Figure 2: Development of compressive strength
Compressive strength.
As can be seen from Figure 2, the compressive strength of
specimens increased by age of specimens.A comparison of the
strength at different ages shows that the rate of strength
development was greater as the age increased. This
phenomenon can be observed by looking to the percentages of
28-day compressive strength for each age in Table 2. The
result shows that the mix achieve 87% of 28-day compressive
strength after 7 days.
Table 2: Compressive strength of full water curing*
Mix
1 day
3 days
7 days
28 days
L
21(45%)
38(81%)
41(87%)
47
*The data in parentheses are percentage of 28 days
compressive strength
Energy absorption.
The number of blows required for the observed first crack was
based on and the ultimate failure was record. The test was
conducted till the crack propagated to the entire depth of slab.
Energy absorption categorized to service (first) energy
absorption (SEA) and ultimate failure energy absorption
(UfEA).
As can be seen from Figure 3 increase the thickness from 20
mm to 30 and 40 mm increase the ultimate failure energy
absorption significantly. There was a strong linear correlation
between UfEA and thickness that can be define by UfEA=
1.9481 T-23.583 with R2 = 0.99, which T is the thickness of
specimens.
Result and discussion
Workability and density.
The slump value of mix L, was about 90 mm and the 28-day
oven dry density of was 2002 kg/m3 which can be consider as
lightweight concrete.
Figure 1: Experimental Set-Up Details
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International Journal of Applied Engineering Research ISSN 0973-4562 Volume 11, Number 9 (2016) pp 6753-6756
© Research India Publications. http://www.ripublication.com
Figure 5: Ultimate crack resistance ratio and thickness
Figure 3: UfEA and thickness
Figure 6: Failure cracks in slab with 40 mm thickness
Figure 4: Ultimate crack resistance and thickness
Failure pattern.
It was observe that specimens with20 and 30 mm thickness
broke into 4 pieces and specimens with 40 mm thickness
broke to 2 pieces at failure. Figure 6 shows the ultimate
failure cracks in specimen with 40 mm thickness.
Ultimate crack resistance.
The average crack resistance for all specimens measured the
crack resistance were calculated and analysed to provide a
clearer picture in understanding the crack behaviour of the
specimens. Figure 4 shows that maximum ultimate crack
resistance has been offered by slabs with 40 mm thickness.
Figure 4shows that the correlation coefficient (R2) was equal
to 0.96 which shows a strong linear relation between ultimate
crack resistance and thickness.
Summary
The relationship of the crack resistance and test parameters
were presented and discussed. The thickness effect on impact
resistance can be define as follows:
By increasing the thickness from 20 mm to 30 and 40 mm the
ultimate energy absorption, 2.4 and 3.6, the ultimate crack
resistance 3.1 and 7.6, and the impact crack resistance ratio 3
and 7 times increased.
Increasing the thickness in the specimen increases the crack
resistance, for both the first crack and ultimate failure.
In general, it can be concluded that increasing the thickness,
increase the impact resistance and crack resistance ratio,
however, it may increase significantly if specimens reinforce
by fibers.
Impact crack resistance ratio.
Specimens with 40 mm thickness had an ultimate crack
resistance ratio of 4.3 which was7 times higher than the crack
resistance ratio of the specimens with 20 mm thickness with
ultimate crack resistance ratio of 0.6 respectively. Figure
5show the crack resistance ratio of each specimen for the
different thickness.
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International Journal of Applied Engineering Research ISSN 0973-4562 Volume 11, Number 9 (2016) pp 6753-6756
© Research India Publications. http://www.ripublication.com
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