HEFAT2012 9 International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics

HEFAT2012 9 International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics
HEFAT2012
9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics
16 – 18 July 2012
Malta
EVALUATION OF TYPE C FLY ASH IN THE PRODUCTION
OF COMPOSITE MATERIAL
Argunhan Z.* , Yıldız T., Çakmak G., Yücel H. L. and Yıldız C.
*Author for correspondence
Batman University, Energy Systems Engineering Department, Batman, Turkey
E-mail: [email protected]
ABSTRACT
In this study, the availability as a new composite material of
the class C fly ashes which have negative effects on
environment was investigated. First of all, the properties of fly
ash and polypropylene have been identified. By making use of
the obtained results, the availability of fly ash and
polypropylene materials was investigated in production of a
new composite material. For this purpose, by using type C fly
ash of thermal power plants in mass ratios of 10% - 60%, a new
composite material was produced. To determine mechanical
and physical properties of the produced composite samples,
thermal conductivity, compressive strength, water absorption
capacity, and abrasive loss were performed. From the results, it
was witnessed that both environmental problems can be
reduced and economical profit can be achieved by means of
energy saving.
The fly ash is also used in the manufacturing of brick, fly
ash mineral-based polymer composites ceramic tableware and
art ware [1-3].
Van Deventer et al. [4] have carried out a series of tests to
produce geopolymers from fly ash. Swamy et al[5] developed
many mixes of normal and lightweight concretes containing
30% of fly ash by weight of cement which provided adequate
early compressive strength compared to the concrete without
fly ash.
Naik and Name [6] provided concrete mixes
containing large quantities of fly ash which achieved
compressive strengths.
Berry et al. [7] suggested that coarse fly ash exhibited low
pozzolanic activity since it contained a high proportion of
crystalline phases.
There have been reports on the utilization of these wastes
for making cementations binders and building products. Li et
al. [8] conducted laboratory tests to evaluate the use of RPM
blended with fly ash in a base course. Mirza et al. [9] noticed
the improvement of stability and the reduction of drying
shrinkage in cement based grouts with fly ash. Glukhovsky et
al. [10] noted the superior properties of his new materials
compared with existing cement-based materials. Fly ash is also
used as an additive in the production of briquettes [11].
The use of fly ash in plastic composites has shown promise
[12], as has application in metal composites, in particular
aluminum [13].
INTRODUCTION
Solid waste management is becoming a challenging
problem for major cities worldwide. Similarly, the fly ash and
waste plastic materials cause environmental pollution.
With this aim, utilization of fly ash as a resource has been
studied for decades in many areas such as in valuable element
extraction, in environmental engineering, in building products,
in plastic industry, in ceramic products.
Fly ash is a waste material resulting from coal being burned
in thermal power plants. Fly ash is one of the residues
generated in the combustion of coal. Total amount of fly ash
produced at coal-fired power plants is about 450 million
tons/year in the world. The amount of fly ash produced in
Turkey is about 15 billion tons/year in 11 coal-fired power
plants.
Plastics are used in our daily lives in a number of
applications. A lot of plastic products are often discarded after a
single use. During last decades, the consumption of plastics
with the great population increase worldwide was increased.
The plastic wastes create vast waste each year to the creating a
serious environmental problem.
NOMENCLATURE
k
MD
MF
ML
MD
MW
WA
WAL
993
[W/mK]
[g]
[g]
[g]
[g]
[g]
[%]
[%]
Thermal conductivity
Mass after drying
Mass before test
Mass after test
Mass after drying
Wet mass after water absorption
Rate of water absorption (%)
Abrasion loss (%)
Benavidez et al. [14] studied the densification of mixtures
of fly ash and bottom ash in different ratios. It was found that
the powders with high fly ash content exhibited higher packing
density and eventually higher sintered density. Xu et al. [15]
studied the effect of fly ash addition on the properties of fired
bricks.
Similarly some studies [16]; have showed that it is indeed
possible to use plastic waste in concretes or mortars.
These research works reported in plastic composite area
include projects on structural and functional evaluation. Plastic
waste represents a raw material for the development of
thermoplastic composites [17].
Yam et al. [18] has evaluated the mechanical properties of
woodfibre–waste plastic composites.
In this study, possible use of C type -Afşin ElbistanThermal
Power Plant fly ash and propylene wastes in a new composite
material was investigated. For this purpose, nine kinds of
composite materials containing 10%-90% Afşin Elbistan
thermal power plant fly ash were produced. Thermal
conductivity, compressive strength, water absorption and
abrasion tests were applied to investigate the mechanical and
physical properties of the fabricated composite material
specimens. In this application, these two waste materials can be
utilized together, both to eliminate environmental problems and
to get economical gains by saving energy.
Table 1. Chemical Composition and Index Properties of Fly
Ashes [22].
Percent of composition
Typical
Typical
Class C
Class F
CaO
24.3
8.7
SiO2
39.9
54.9
Al2O3
16.7
25.8
Fe2O3
5.8
6.9
MgO
4.6
1.8
SO3
3.3
0.6
CaO/SiO2 ratio
0.61
0.16
Loss on ignition (%)
6
6
Classification (ASTM 618)
C
F
Polypropylene
Polypropylene is a thermoplastic polyolefin that is produced
by polymerizing propylene monomer, which is a gaseous
byproduct of petroleum refining, in the presence of a catalyst
under controlled heat and pressure [23].
Polypropylene, with the chemical formula (C3H6)x ( Figure
1), is a thermoplastic polymer used in a wide variety of
applications including packaging, plastic parts, laboratory
equipment, automotive components etc. Crystallinity property
and Young‘s Modulus of polypropylene is between that of low
density polyethylene and high density polyethylene. It is less
tough but also less brittle than high density polyethylene, this
allows polypropylene to be used as an engineering plastic.
Resistances to fatigue, high melting point (130-168 °C) and
relatively low cost are the other superior properties of
polypropylene.
Class C fly ash
Fly ashes may be sub-divided into two categories, according
to their origin (ASTM) [19]:
Class F : Fly ash normally produced by burning anthracite
or bituminous coal which meets the requirements applicable to
this class.
Class C : Fly ash normally produced by burning lignite or
sub-bituminous coal which meets the requirements applicable
to this class. Class C fly ash possesses some cementations
properties. Some Class C fly ashes may have lime contents in
excess of 10 % [20].
Physical properties of fly ash mainly depend on the type of
coal burned and the burning conditions. Class F fly ash is
generally produced from burning high rank (containing high
carbon content) coals such as anthracite and bituminous coals,
whereas, Class C fly ash is produced from low rank coals.
Its physical and chemical properties depend exclusively on
the quality of coal used and on technological conditions of
burning [21].
Physical and compositional properties of the fly ashes are
summarized in Table 1 along with typical physical properties of
Class C and F fly ashes.
While Class F fly ash is highly pozzolanic, meaning that it
reacts with excess lime generated in the hydration of portland
cement, Class C fly ash is pozzolanic and also can be selfcementing. ASTM C618 requires that Class F fly ash contain
at least 70% pozzolanic compounds (silica oxide, alumina
oxide, and iron oxide), while Class C fly ashes have between
50% and 70% of these compounds.
Figure 1. Molecular structure of polypropylene chain.
Due to its non-polar nature, polypropylene has high
resistance to most solvents and chemicals and also good
resistance to moisture. Non-polar structure also makes PP
hydrophobic and makes polar clay minerals and layers difficult
to disperse in it. It‘s highly crystalline nature provides high
tensile strength, stiffness and surface hardness to
polypropylene.
Polypropylene is a lightweight plastic that is rigid and
tough. Combined with its low cost, polypropylene is used in a
wide variety of applications. The polypropylene has a semicrystalline structure that offers good mechanical properties such
as stiffness and tensile strength. When combines with different
fillers such as clay, talc, calcium and glass, the mechanical
properties of polypropylene can be dramatically enhanced. The
994
addition of 30% short fiber glass reinforcement increases
tensile strength and doubles the impact resistance [24]. Table 2
furnishes some mechanical properties of polypropylene
homopolymer.
Polypropylene is useful a wide range of applications
because of its properties.






A unique aspect of the polypropylene processes, compared
to the other major plastics, is the use of orientation to develop
enhanced properties, principally in fibers and films, constituting
nearly one-half of the consumption. None of the other major
plastic materials uses orientation to any appreciable extent,
except PET, which is considered a major plastic, where
orientation is used in fibers, biaxially oriented films, and soda
bottles, and nylon, which is oriented into fibers. Lesser but
significant quantities of polypropylene are used in unoriented
film, sheet, and blow molding.
Fairly low physical properties
Fairly low heat resistance
Excellent chemical resistance
Translucent to opaque
Low price
Easy to process
EXPERIMENTAL
Materials
Table 2. Selective properties of polypropylene
Property
Tensile strength, MPa
36
Elongation at break. %
350
Flexural modulus, MPa
1310
Brittle temperature, 0C
+15
0
Softening point, C
145-150
Hardness, (R-scale)
95
Impact strength,kJ/m2
24.5
MFI, g/10 min
8.7 (2.16 kg/230 0C)
Fly ash from the Afşin Elbistan Power Plant in Turkey was
used in this study. According to ASTMC 618 [19], Fly ash
from Afşin Elbistan can be classified as class-C Fly ash
because it has an S+A+F higher than 50% and lower than 70%.
In addition, recycled polypropylene was obtained from post
consumer plastic products and was used as the matrix material.
This ASTM class ‗C‘ fly ash (as per ASTM-C 618) was
found to have different proportions of oxides. The chemical
composition of Afsin-Elbistan fly ashes is given in Table 3. In
addition major physical properties of these fly ashes are shown
in Table 4.
Polypropylene is transformed into useful products by a
wide variety of processes, which has been, together with a
suitable cost/performance balance, a major factor in its
commercial success. Figure 2 shows the breakdown of global
sales among the major processes. The ease of molding and the
attractive strength, stiffness, and high use temperatures of
articles molded of polypropylene have made injection molding
the largest consumer of polypropylene among the processes
used.
Table 3.
ashes[26].
Chemical composition of Afsin-Elbistan fly
Element oxide
SiO2
Al203
Fe203
CaO
MgO
K2O
Na2O
TiO2
SO3
Cd*
Pb*
Zn*
Cub
Cr*
Nib
Mn*
LOI
Figure 2. Breakdown of polypropylene demand by end-use
[25].
995
(%)
15.14
7.54
3.30
23.66
4.50
0.28
0.57
1.03
13.22
8.0
79.6
79.6
39.8
298.4
119.4
218.8
2.31
Table 4 Major physical properties of Afsin-Elbistan fly ashes
[26]
pH
12.5
Particle size
65% ≤75 µm
Specific surface area (m2/g)
0.342
Bulk density (g/cm3)
1.05
Specific gravity (g/cm3)
2.70
pHZPC
7.0
LOI
2.31
The abrasion losses of the samples were tested. The abrasion
loss values are determined following equation.
WAL = [(MF – ML) / MF] × 100
(2)
RESULTS AND DISCUSSION
A typical SEM photo of fly ash and polypropylene samples
is shown in Figure 3. The figure showed that the fly ash
particles are smoothly encapsulated in polypropylene.
Experimental procedure
The fly ash and the recycled polypropylene samples were
taken in six ratios. Six groups of mixes of fly ash and
polypropylene were produced. The percentage ratios of the
weights of fly ash are 10, 20, 30, 40, 50 and 60. They were
specified as Table 5.
Table 5. Ratios of the weights of fly ash and polypropylene
Label
Material (%)
% FA
% PP
AFP10
10
90
AFP20
20
80
AFP30
30
70
AFP40
40
60
AFP50
50
50
AFP60
60
40
The fly ash and the polypropylene were mixed in an internal
mixer for 30 min at a temperature of 200oC. The concrete
mixes were prepared as homogeneity. For each mixture, these
different samples were prepared for measuring mechanical
properties, moist, density, the loss in weight and their thermal
conductivities.
Tensile tester was used to measure tensile properties. The
tensile tests were performed as per TS 699(Model BC100). At
least three specimens were tested for each variation in the
composition of the composites. The maximum rate of pressure
applied for samples was 200 t.
The thermal conductivity coefficient of the samples was
carried out for using Hot-Wire instrument as per DIN51046
(Showa Denko). Its sensitive is given as 5% digit and the
measurement range is stated as 0.02-10 W/mK [2].
The samples for water absorption were placed in a water
tank at room temperature. The samples after a certain periods
were removed from water. The percentage weight gain of the
samples was measured. These samples were in an open
atmosphere for three days. The rate of water absorption of
samples was calculated using the following equation:
Figure 3. SEM photo of the composite material with
polypropylene and 50% of fly ash
The thermal conductivity coefficient (k) is computed by
using the average of these five k values and it is shown in
Figure 4.
0,5
k (W/mK)
0,45
0,4
0,35
0,3
0,25
0,2
WA = [(MW – MD) / MD] × 100
(1)
0
10
20
30
40
50
60
70
Fly ash(%)
On the samples, surface abrasion loss (Bohme) tests are
performed using TS 699. For the determination of Bohme
abrasion loss was prepared samples in compliance with TS 699.
Figure 4. The thermal conductivity coefficient and
fly ash relation
996
Figure 7 shows the influence of total mass on the water
absorption as a function of time. It is shown that increasing the
percentage of fly ash leads to the increase of water absorption.
The water absorption of the all samples achieved in the limits
of TSE.
300
250
200
Mass (gr)
Compressive strength (kp/cm2)
This figure demonstrates that the thermal conductivity with
increasing fly ash was decreased. The results in Figure 4
indicate that reductions in thermal conductivity are possible by
incorporating high volumes of fly ash into polypropylene. The
lowest value of the thermal conductivity is obtained for sample
with 60% fly ash. This reduction in thermal conductivity is
related to the increase of porosity.
The compressive strength values are presented in Figure 5.
The compressive strength values are inversely proportionate
with the percentages fly ash. The highest compressive strength
was measured in the sample with 10% fly ash and 90%
polypropylene which was 106 kp/cm2.
120
AFP10
AFP20
AFP30
AFP40
AFP50
AFP60
150
100
100
50
80
0
60
0
5
10
15
20
25
30
Time(h)
40
20
Figure 7. Total mass change on water absorption as depending
on time.
0
0
10
20
30
40
50
60
70
CONCLUSION
Fly ash(%)
The aim of this study was to investigate the usability of fly
ash and polypropylene as building material. As a result of this
experimental study provided the following conclusions.
It was suggested that fly ash could be an alternative filling
material for polypropylene. In overall, the mechanical
properties of product obtained of the polypropylene were
affected positively.
The changes in the thermal properties and the mechanical
properties of new material obtained were explained by the
differences in the composition and shape of the fly ash
particles. It was observed that additive of polypropylene and fly
ash increased strength and decreased thermal conductivity
coefficient from test results. The minimum thermal
conductivity coefficient value was founded for 60% fly ash and
40% polypropylene.
Reducing the thermal conductivity coefficient increases the
insulation value provided by the composite, potentially
contributing to a reduction in heating and cooling costs for
residential and commercial buildings constructed
Wastes are gained to economy and environmental
contaminant is decreased owing to usage of polypropylene and
fly ash on a new building materials. Since this composite
material has low density and thermal conductivity coefficient, it
could potentially be used as an alternative lightweight building
material.
Figure 5. The compressive strength and fly ash relation
The abrasive loss determined for samples shown in Figure
8. The lowest value of the abrasive loss was determinate for
sample produced with 10% fly ash. The compressive strength
values with the abrasive loss values are shown similar result.
1,8
1,6
Abrasive loss (%)
1,4
1,2
1
0,8
0,6
0,4
0,2
0
0
20
40
60
80
Fly ash(%)
Figure 6. Abrasive loss and fly ash relation
997
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