Investigations of the Influence of Polystyrene Foamed Granules on the Properties of Lightweight Concrete

Abstract

This paper deals with the behaviour of cement paste upon the addition of crushed polystyrene foam. Crushed polystyrene foam waste with a fill density of 13.97 kg/m 3 and hydrated lime were used to prepare the foam. Three different types of samples S-1, S-2, and S-3 were prepared to observe the behaviour of cement pastes after the addition of different doses of foam in constant water/cement ratio. The volumetric ratio of EPS and cement paste were 1: 1.294; 1: 0.863; and 1: 0.647. In each type of sample, 0.28 water/cement ratio is maintained. Slump test was carried out in the fresh state and it has been found slump value was decreasing by increasing foam content in concrete sample. On the 7 th and 28 th day of curing process, the compressive strength test was carried out. Compressive strength and density of concrete samples also decreasing by addition of higher foam content. In addition, water absorption test and microscopic analysis tests were carried out on the 28 th day of curing process. It has been found from the study that samples thermal conductivity is working proportionally.

Full text

JOURNAL OF APPLIED ENGINEERING SCIENCES VOL. 9(22), ISSUE 1/2019
ISSN: 2247-3769 / e-ISSN: 2284-7197 ART.NO. 248 pp. 19-24
INVESTIGATIONS OF THE INFLUENCE OF POLYSTYRENE FOAMED
GRANULES ON THE PROPERTIES OF LIGHTWEIGHT CONCRETE
ADHIKARY Suman Kumar a, *, RUDZIONIS Zymantas a, ZUBRUS Marijus a
a Kaunas University of Technology, Civil Engineering and Architecture, e-mail: sumankradk9s@gmail.com
Received: 24.12.2018 / Accepted: 14.03.2019/ Revised: 11.04.2019 / Available online: 31.05.2019
DOI: 10.2478/jaes-2019-0002
KEY WORDS: Lightweight concrete; thermal conductivity; polystyrene foam concrete; Microscopic analysis.
ABSTRACT:
This paper deals with the behaviour of cement paste upon the addition of crushed polystyrene foam. Crushed polystyrene foam waste
with a fill density of 13.97 kg/m3 and hydrated lime were used to prepare the foam. Three different types of samples S-1, S-2, and S-
3 were prepared to observe the behaviour of cement pastes after the addition of different doses of foam in constant water/cement
ratio. The volumetric ratio of EPS and cement paste were 1: 1.294; 1: 0.863; and 1: 0.647. In each type of sample, 0.28 water/cement
ratio is maintained. Slump test was carried out in the fresh state and it has been found slump value was decreasing by increasing
foam content in concrete sample. On the 7th and 28th day of curing process, the compressive strength test was carried out.
Compressive strength and density of concrete samples also decreasing by addition of higher foam content. In addition, water
absorption test and microscopic analysis tests were carried out on the 28th day of curing process. It has been found from the study
that samples thermal conductivity is working proportionally.
* Corresponding author: Suman Kumar Adhikary, e-mail: sumankradk9s@gmail.com
INTRODUCTION
The whole world pays great attention to the environmental
protection and is trying to recycle waste materials. Every year
the amount of the polystyrene waste is increasing and ultimately
causing environmental pollution and harm the ecosystem.
Polystyrene also known as EPS (Expanded polystyrene) is
highly popular material used as packaging and insulation
material. Polystyrene is large and bulky in nature and takes
significant space for disposal. This material is also non-
biodegradable and cannot be disposed easily. On the other
hand, this material is lightweight with good thermal and sound
insulation properties [1, 2, and 3]. The density of expanded
polystyrene is extremely light and the it varies 12-20 kg/m3. So,
this material has gained great popularity in construction
industry. Waste polystyrene can be used in construction
industry as various options like preparation of lightweight
concrete, as aggregates and foams [4, 5, and 6]. Generally
convectional concrete density is around 2400 kg/m3 and
lightweight concrete is subjected to having density around 1800
kg/m3 or less [7]. There are several materials used to prepare
lightweight concrete such aluminum powder (foaming agent),
mineral lightweight aggregates (vermiculite perlite, pumice,
slate, expanded shale, etc.), polymer materials and other
lightweight aggregates [8, 9]. Polystyrene based light weight
concrete was firstly tested in 1996 by Dr. Z. Kuhai [10].
Researcher WU Zhen achieved light weight concrete with the
density of less than 500 kg/m3 by replacing fine aggregate by
EPS foam and found in his experimental studies that
compressive strength of EPS foam-based concrete is
proportional to its bulk density [11]. Several studies have been
conducted with polystyrene and other admixtures in concrete
like fly ash, different types of fibers, silica fume, polymeric
admixtures etc. [12, 13, and 14]. Polystyrene aggregates are
commercially available worldwide while most of the plants are
concentrated in Europe and Russia [15]. It has been found that
EPS aggregate concrete has higher compressive strength with
fire resistance properties than perlite aggregate concrete [16].
EPS concrete have various beneficial aspects and its strength
can be improved by adding some admixtures. The main purpose
of this paper is quantifying the influence of the concrete under
various EPS foam doses.
MATERIALS AND PROPORTIONS OF MIXING
Ordinary Portland cement named ‘Akmenės Cementas AB’ of
grade CEM I 42.5R satisfying EN 197-1:2011 was used.
Crushed polystyrene foam granule of 13.97 kg / m3 density and
hydrated lime were used to prepare the foam. To prepare the
foam, crushed polystyrene and water were used in a ratio of 1:4
by volume and 20% hydrated lime of its volume used. Water
crashed polystyrene and hydrated lime mixed with compressor
airflow to produce foam. Afterwards foam was mixed with
cement paste manually by hand and proceed for slump test and
moulding process which is showed in Figure 1. The
composition of all samples can be seen in Table 1.
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ISSN: 2247-3769 / e-ISSN: 2284-7197 ART.NO. 248 pp. 19-24
Table 1. The mixing composition the samples for 1 m3 concrete
Type of
samples
Cement
quantity, kg
Amount
of water,
kg
Foam
quantity, kg
S-1
875.0
366.7
21.3
S-2
841.2
352.5
30.4
S-3
656.7
275.2
31.6
Figure 1. Mmixing foam with cement morter and Moulded
concrete
MECHANICAL PROPERTIES EVOLUTION
Slump
Slump test was carried out after mixing the cement paste in
fresh state by using Sutardo viscosimeter satisfying GOST
(23789-85) standard. Sutardo viscosimeter is a cylindrical
shaped equipment having 57 mm external diameter with 50 mm
internal diameter and 99.5 mm of height. Slump test of each
type of specimens were carried out in two stages. Firstly,
slump test was carried out without foam content and in the 2nd
stage, foam was mixed with the cement paste. The slump test
was carried out in two stages to determine the difference of
slump value when foam is added to the concrete. From the
study, it has been found that slump value of the mixture
decreases with increasing foam. By increasing the volume of
foam up to their volumetric concentration with a 1: 0.436
cement, the spread of the mixture decreased by 18.75%. This
could be explained by the fact that by increasing the amount of
foam the water absorption also increases and results less slump
value. The result of slump test can be seen in Figure 2.
Figure 2. Slump test of concrete samples
Compressive strength
After the slump test all the samples were moulded in 7.07 cm x
7.07 cm x 7.07 cm size cubes to determine the water absorption
test, density, compressive strength. Each type of samples was
prepared in three same specimens and average value was taken
as result. The molding samples were kept in room temperature
for 24 hours for the hardening process. After hardening process,
all samples were kept in curing chamber (temperature 20 ± 2 C
and relative humidity 95% or more) till the day of test.
Compressive strength test was conducted on 7th and 28th day of
curing process satisfying LST EN 12390-3: 2001 norms. Before
testing the strength properties, the samples were removed from
curing chamber and kept 1 to 2 hours in room temperature. The
results of the compressive test showed in Figure 3. From the
results of the study it has been found that the compressive
strength decreases with increasing the amount of crushed
polystyrene foam granules. This can be explained by the fact
that the strength of the polystyrene foam granules is less than
heavy aggregates. Therefore, the strength properties of the
specimens were reduced.
Figure 3. Compressive strength test of concrete samples on 7th
and 28th day
Density test
The average density of specimens was determined in fresh and
hardened state. After the curing process on 28th day water
immersed concrete samples were taken out from the climatic
chamber and dried in room temperate for 6 hours. After the
drying process concrete samples density were calculated. From
the result it has been found that density and doses of
polystyrene foam is inversely proportional. It means the density
of concrete specimen’s decreases with the increasing volume of
polystyrene foam in the concrete mixture. Figure 4 shows the
density of concrete samples on fresh and hardened state.
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Figure 4. Density of concrete samples
Water absorption test
The water absorption of samples was determined according to
the requirements of LST EN 1353: 2000. The specimens were
placed in water and weighed in balance after 15 min, 1h, 24h
and 48h, and weighed by hydrostatic balance. From the results
of the study it is seen that the water absorption of the specimens
increases rapidly in the first minutes of soaking (up to 15
minutes), which indicates that the pores are predominant in
porosity with the aid of a foam. Figure 5 shows the water
absorption of concrete samples.
Figure 5. Water absorption test of concrete samples
3.5 Heat transfer coefficient of specimens
The thermal conductivity coefficient of the samples was
determined according to STR 2.01.03: 2003 showed in Figure
6. After calculating the curve, which is given in Figure 7, the
thermal conductivity coefficients of the samples are deduced
according to the curve equation. The coefficient of
determination R2 = 0.9925.
Figure 6. Thermal conductivity coefficient chart by density of
samples
0.89 0.83
0.54
0
0.2
0.4
0.6
0.8
1
S-1 S-2 S-3
Thermal conductivity
coefficients λ,
W/(m∙K)
Type of samples
Thermal conductivity coefficients of the
samples
Thermal conductivity coefficients
Figure 7. Calculated thermal conductivity coefficients of
samples
1.6 Microscopic analysis
Microscopic analysis of concrete provides information about
microstructure of concrete and mineral constituents. Material
scanning electron microscopy (SEM) was performed using the
FEI QUANTA 200F microscope. The FEI Quanta 200 FEG's
high-resolution scanning electron microscope provides an
Outdoor Schottky Area Cannon (FEG). The following operating
conditions were used for scanning: high vacuum (HV) mode - 5
kV. The microscopic analysis was carried out on samples S-1,
S-2, and S-3. The analysis was carried out on samples bulk of
the texture. Microscopic analysis and EDX (Energy-Dispersive
X-Ray) analysis of sample S-1, S-2, and S-3 are shown in
Figure 8 and Figure 9, Figure 10, Figure 11, Figure 12 and
Figure 13.
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JOURNAL OF APPLIED ENGINEERING SCIENCES VOL. 9(22), ISSUE 1/2019
ISSN: 2247-3769 / e-ISSN: 2284-7197 ART.NO. 248 pp. 19-24
Figure 8. Sample S-1 micscopic analysis on the bulk texture
Figure 9. Sample S-1 Energy-Dispersive X-Ray analysis
Figure 10. Sample S-2 micscopic analysis on the bulk texture
Figure 11. Sample S-2 Energy-Dispersive X-Ray analysis
Figure 12. Sample S-3 micscopic analysis on the bulk texture
Figure 13. Sample S-3 Energy-Dispersive X-Ray analysis
1.7 X-ray diffraction analysis
X-ray diffraction is a very useful technique to identify the
crystalline phases of cement in concrete [17]. X-ray diffraction
analysis was performed using the DRON-6 diffractometer.
CuKa radiation, Ni filter was used for the test, detector
movement step was 0.02°, intensity measurement 0.5 s, anode
voltage Ua = 30 kV, current I = 20 mA. The diffraction curves
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were additionally recorded in the range of 2  60o 2 angles
using a flat-end graphite monochromator (d = 0.355 nm) and
measuring the intensity  = 1 s. X-ray diffraction analysis was
performed on samples S-1, S-2 and S-3. The results of the study
are presented in Figure.14 X-ray images of the specimens have
identified the diffraction peaks that are characteristic of
Portlandites(P), Calcium carbonate(C), Alitas(A), Vateritas(V),
Etringitas(E). From the Figure 14 it can be clearly observed that
the Portlandite is at peak level at 18° for sample S-1 while
samples S-2 and S-3 have lesser peak level. On the other hand,
Alitas was at peak level at 29.1°for sample S-3 while samples S-
1 and S-2 show lesser peak level.
Figure 14. X-ray diffraction analysis curves of samples
4. CONCLUSION
From the study it has been found that the workability of
polystyrene foamed concrete depends upon the ratio of
polystyrene foam and cement paste. Density, compressive
strength of the concrete is inversely proportional to the doses of
polystyrene foam in the concrete. Concrete’s density and
strength decreases when the amount of polystyrene foam
increases in the concrete mixture. Samples S-1, and S-2 have
better compressive strength compared to S-3. On the other
hand, S-3 has better thermal insulation conductivity. Sample S-
3 can be used in construction sector because it has enough
strength properties and thermal conductivity coefficient. The
insulation and strength properties of polystyrene foamed
concrete can be improved by using micro fillers and thermal
insulating admixtures like aerogel. In future, further study will
be carried out to achieve higher strength and thermal
conductivity in lightweight concrete. And new materials like
aerogel, carbon aerogel will be developed and used in light
weight and ultra-light weight concrete to achieve better thermal
coefficient.
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