-
http://www.iaeme.com/IJCIET/index.asp 1962 [email protected]
International Journal of Civil Engineering and Technology
(IJCIET)
Volume 9, Issue 7, July 2018, pp. 1962–1974, Article ID:
IJCIET_09_07_209
Available online at
http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=9&IType=7
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication Scopus Indexed
GEOPOLYMER EFFECT IN MODELLING
HYDRAULIC CONDUCTIVITY FOR
DESIGNING SOIL LINER OF LATERITE SOIL
M. Mukri
Civil Engineering Department, UiTM Shah Alam - 41450, Shah Alam,
Malaysia
N. N. S.Aziz
Faculty of Civil Engineering, UiTM Shah Alam- 41450, Shah Alam,
Malaysia
N. Khalid
Civil Engineering Department, UiTM Shah Alam - 41450, Shah Alam,
Malaysia
ABSTRACT
Soil liners are commonly used in the base of waste containment
facilities and it
has been used for many years. The previous studies revealed that
the soil liner should
have a hydraulic conductivity lower than 1x10-9
m/s. Laterite soil is the main material
used for soil liner. However, the use of laterite soil
associated with difficulties in
compacting to achieve the acceptable hydraulic conductivity.
Laterite soil was
modified with the chemical stabilizer which is fly ash based
geopolymer. Laterite soil
was mixed with different percentages of geopolymer which are 5%,
10%, 15% and
20% by weight. The NaOH in pellets form was added to water in
order to obtain the
alk ali solution and fly ash was added to the solution to form a
material in a binder
state k nown as geopolymer. The soil properties were also
determined for all soil
samples. The hydraulic conductivity of soil was determined by
using a falling head
permeability test subjected to BSL test only. All compacted
samples were performed at
dry, optimum and at wet of optimum moisture content. The
hydraulic conductivity for
the soil sample that compacted with RBSL test and BSH were
determined by using
Benson and Trast’s formula. According to the results, it was
found that the soil
mixture with 15% of geopolymer gives the best value of hydraulic
conductivity of the
soil. Subsequently, models of estimating hydraulic conductivity,
k from an empirical
formula based on soil parameter measured in the laboratory were
established. The
models were developed by using MINITAB software. There are a few
parameters that
were used in developing the models. A model was developed based
on physical
properties parameters to predict the hydraulic conductivity of
the modified soil based
geopolymer. Further adding geopolymer in the soil mixes was
found decreased the
hydraulic conductivity of the resulted liner.
Key words: Laterite Soil, Geopolymer, Hydraulic Conductivity and
Empirical
Formula.
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M. Mukri, N. N. S.Aziz and N. Khalid
http://www.iaeme.com/IJCIET/index.asp 1963 [email protected]
Cite this Article: M. Mukri, N. N. S.Aziz and N. Khalid,
Geopolymer Effect in
Modelling Hydraulic Conductivity for Designing Soil Liner of
Laterite Soil.
International Journal of Civil Engineering and Technology, 9(7),
2018, pp. 1962-
1974.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=9&IType=7
1. INTRODUCTION
Soil liners are generally used in the base of waste containment
facilities and it has been as
such for many years. There are three (3) types of soil liners
normally applied, which are
natural undisturbed clayey deposits, compacted soil liners and
geosynthetic clay liners [29]. A
low hydraulic conductivity is a key parameter in the design of
liner to prevent the downward
migration of contaminants into aquifers. Besides that, Stewart
and Nolan, [31] explained a
landfill liner should have low hydraulic conductivity, good
resistant to shrink age crack ing
and have suitable mechanical properties for structural integrity
during construction and
operation. Benson et al. [8] from their studies suggested that
the soil liner should have a
hydraulic conductivity lower than 1x10-9
m/s. The thickness of compacted soil liners usually
0.6 m to 3 m, consisting natural soil. This natural soil is
recompacted in the field to obtain the
desired hydraulic strength properties.
Good engineering practice and quality assurance program can
result in good quality and
low hydraulic conductivity soil liners [29, 37]. The hydraulic
conductivity of compacted soil
liners depends on the soil mineralogy and the mode of placement
of the liner. Examples of
soil liners and cover system used in the liner are shown in
Figure 1 and Figure 2. Based on
Figure 1, Rowe [29] and Mukri [38] stated that liners may be
described as single composite
liner systems and double composite liner. Single composite liner
system consists of
geomembrane in combination with a compacted soil liner. This
type of liner system is
required in a municipal waste landfill because it is effective
at limiting leachate migration into
the subsoil. Other than that, double composite liner system
consists of either two single liners,
two composite liners or both single and composite liners. The
functions of upper and lower
liners are different. On the other hand, Figure 2 shows the
typical cover system. This system
is important to cover the waste in order to prevent water
ingress into the waste and therefore
to limit future leachate generation. The topsoil that covers the
waste comprises of compacted
soil with low permeability.
Figure 1 Examples of compacted soil liners (typical liner
system) [29].
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Geopolymer Effect in Modelling Hydraulic Conductivity for
Designing Soil Liner of Laterite Soil
http://www.iaeme.com/IJCIET/index.asp 1964 [email protected]
1.1. Laterite Soil
Laterite soil is one of the residual soils. Gidigasu and Kuma
[14] stated the term
“Laterization” describes the processes that produce laterite
soils. Lateritic soils usually
develop in tropical and other regions with similar hot and humid
climate, where heavy
rainfall, warm temperature and well drainage lead to the
formation of thick horizons of
reddish lateritic soil profiles rich in iron and aluminium [23,
32, 7]. According to Gidigasu
and Kuma [14], a lateritic soil profile is characterized by the
presence of three major horizons
include the sesquioxide rich lateritic horizon, the mottled zone
with evidence of enrichment of
sesquioxide and the pallid or leached zone overlying the parent
rock . Lateritic soils have a
varieties colour from ochre through red, brown and violet to
black . According to Safiuddin et
al. [30], the colour of the soils depends largely on the
concentration of iron oxides and the
presence of hematite and goethite. If soil sample consists high
amount of iron oxides, the
sample of laterite gives reddish to brown in colour. Figure 2
show the profile of laterite soil.
Figure 2 Profile of Laterite Soil (Encyclopedia Britannica)
In addition, Maigien [20] and Gidigasu [13] stated laterite soil
are weathered under
conditions of high temperatures and humidity resulting in poor
engineering properties such as
high plasticity, tendency to retain moisture and high natural
moisture content.
Frempong and Yanful [12]; Osinubi and Nwaiwu [25] ; Ahmad et al.
[39] and Osinubiet
et al. [26] mentioned that when laterite soil was compared with
active clay soils, it presents
attractive option because of its greater shear strength
properties, chemical resistance, better
work ability and availability where they occur in abundance. In
addition, the positive and
extensive experience of using lateritic soil in several
geotechnical structures such as highway
embankments, road bases, airport runways, earth dams etc for
several decades has encouraged
research in the use of the soil as material for soil liners [4].
However, the soil has high
hydraulic conductivity apparently due to the predominance of
inactive and non-expanding 1:1
kaolinite clay mineral in the soil [20, 13, 4].
Laterite soils in the landfill area cannot perform
satisfactorily as a barrier because of its
high hydraulic conductivity. Hence, modification of soils to
improve their engineering
properties becomes necessary. Numerous studies have been
conducted on the permeability of
the lime-treated soil, cement-treated soil and fly ash-treated
soil but data on the use of
geopolymer is still lacking. The focus of this study is to
examine the suitability of geopolymer
to enhance lateritic soils as soil liner.
https://global.britannica.com/editor/The-Editors-of-Encyclopdia-Britannica/4419
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M. Mukri, N. N. S.Aziz and N. Khalid
http://www.iaeme.com/IJCIET/index.asp 1965 [email protected]
2. MATERIAL AND EXPERIMENTAL PROCEDURES
2.1. Geopolymer
Douglas et al. [10] and Cristelo, Glendinning, Fernandes and
Pinto [9] mentioned that
geopolymers are inorganic binders consisting of two components
which are very fine and dry
powder and syrupy, highly alkaline liquid. In order to produce a
mixture of molasses-like
consistency which is then reacted with the desired waste or
aggregate, the liquid and powder
portions are mix together [10].
Cristelo et al. [9], stated that in geotechnical applications,
alkaline activation which is a
geopolymeric binder of fly ash was tested for soil improvement
since the waste material was
obtained as a binder in most of the other geopolymer
applications. Alkaline-activated
materials showed better performance since durability and
stability can be increased, an
improvement from a mechanical aspect compared to cement and also
improved the bond
between the soil particles and binder [27, 34]. Alkaline
activation generally was a reaction
concerning alumina-silicate materials and alkali or earth
substances alkali. At a molecular
level to natural rocks, materials formed from reactions between
silica, alumina and alkali
cations were very alike in term of stiffness, durability and
strength (Cristelo et al., 2012) [9].
Referring to Hamidi et al. [16], based on Zhang et al. [36],
they mentioned that research
on this inorganic polymer widens where it shows promising use in
various application namely
toxic metal immobilization, waste management, fire resistance,
construction repair and
coatings. Moreover, it is a green material because it comes from
industrial waste and natural
resource. Furthermore, the other advantages of geopolymer are
that their product is very
economical and cost-effective because the waste is available at
low cost and the process is
hassle-free [17].
According to Komnitsas [19], any aluminosilicate source (such as
metak aolin, kaolin,
slag and fly ash) that can dissolve in alkaline activator
solution (such as NaOH or KOH) will
act as geopolymer precursor and geopolymerise. Most of the
researchers more interest to
utilize industrial byproduct material such as slag and fly ash
as the source materials for
geopolymer because they have high silica and alumina contents
which also abundantly
available in landfill site [24]. Whereas, the alkaline solutions
play role in geopolymerization
at the early stage as it dissolves the active aluminosilicate
species in the reaction [18].
Nikolic et al. [22] reported that fly ash is of coal fire
by-product material from the coal-
fired power station. Ansary et al. [5] acknowledged that fly ash
is regularly used as a partial
replacement for cement in concrete because of its pozzolanic
properties. Besides that, it is
also the form of ash, which has the greatest potential for use
in the ground modification.
There are two classes of fly ash are defined by ASTM C618 which
is Class F fly ash and
Class C fly ash. The differences between these classes of fly
ash are the amount of calcium,
silica, alumina, and iron content in the ash. The chemical
properties of the fly ash are largely
influenced by the chemical composition of the coal burned. The
additions of a chemical
activator such as sodium silicate (water glass) to a Class F ash
can lead to the formation of a
geopolymer. Furthermore, class C fly ash is produced from the
burning of younger lignite or
subbituminous coal. Unlike Class F, self-cementing Class C fly
ash does not require an
activator. Alkali and sulfate (SO4) contents are generally
higher in Class C fly ashes.
Sodium hydroxide is one of the materials that are used to
produce geopolymer binder. It
consists of two different states which are in solution form or
in pallet form. In a solution form,
sodium hydroxide is a white, odorless, and non-volatile
solution. It is highly reactive but does
not burn. It reacts violently with water and numerous commonly
encountered materials,
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Geopolymer Effect in Modelling Hydraulic Conductivity for
Designing Soil Liner of Laterite Soil
http://www.iaeme.com/IJCIET/index.asp 1966 [email protected]
generating enough heat to ignite nearby combustible materials
[3]. The advantages of
geopolymer are it can easily react with water which results in a
powerful compaction aid thus
giving a higher density for the same compaction effort. Sodium
hydroxide reacts very
effectively with soil rich in aluminum [3].
Harditjo et al. [15] stated that an alkaline activator that
commonly used in producing
geopolymer is a combination of sodium hydroxide (NaOH) or
potassium hydroxide (KOH)
and sodium silicate or potassium silicate. This alkaline
solution plays an important role [21].
An alkaline solution is chosen depends upon various factors such
as the cost and the reactivity
of the alkaline solutions [21]. The dissolution of fly ash is
affecting due to the type and
concentration of alkaline solutions. Generally, the Al3+ and
Si4+ ions are leaching highly
with sodium hydroxide solution compared to the potassium
hydroxide solution. Duchesne,
Duong, Botrom and Frost [11] mentioned that in presence of NaOH
in the activating solution,
the reaction proceeds more rapidly and the gel is less smooth.
The gel composition analyzed
in the sample activated with the mixture of sodium silicate and
sodium hydroxide is enriched
in Na and Al [2].
Xu and Van Deventer [35] studied a wide range of aluminosilicate
minerals to make
geopolymers. They found that generally, the sodium hydroxide
solution caused a higher
extent of dissolution of minerals than the potassium hydroxide
solution [21].
2.2. Experimental Procedure
This study involves with several laboratory works. First, the
laterite soil was collected at
Damansara Perdana area. Then, the geopolymer was produced by
mixing fly ash with an
alkali activator, sodium hydroxide (NaOH). Sodium hydroxide was
purchased from the
supplier and the fly ash was collected from Kapar Energy
Ventures Sdn. Bhd. Kapar
Selangor. The sodium hydroxide (NaOH) in pellet form was added
to water in order to obtain
the alkali solution and fly ash was added to the solution to
form a material in a binder state
known as geopolymer.
Next, the soil properties were determined by conducting
Atterberg limit, particle density,
particle size distribution, pH, and shrink age limit test to
determine the physical properties of
laterite soil before and after mixing with different percentage
of geopolymer. From this
preliminary laboratory works, the parameters collected include
liquid limit (LL), plastic limit
(PL), plasticity index (PI), specific gravity of soil (Gs) and
pH of the soil. Then, shrinkage
limit test was carried out to identify the shrinkage index of
laterite soil.
The next test was falling head permeability test. This test was
carried out to determine the
hydraulic conductivity of soil mixed with different proportions
of geopolymer subjected to
British Standard Light (BSL) of compaction. There were 15
samples prepared, and these
compacted soil samples were performed at dry, optimum and at wet
of optimum moisture
content. The hydraulic conductivity of soil that had been
compacted with Reduced British
Standard Level (RBSL) and British Standard Heavy (BSH) test was
determined using the
empirical models that had been developed by the previous
researcher. The falling head
permeability test was not carried out on laterite soil that had
been compacted with Reduced
British Standard Level (RBSL) and British Standard Heavy (BSH)
tests because of time
constraint. In this study, one (1) soil sample required about
four (4) months to saturate and
can be used to determine its hydraulic conductivity.
Last but not least, the collected laboratory data were analyzed
using MINITAB 14. This
software was used to develop a model of hydraulic conductivity
effected by geopolymer, k(%
geopolimer). These models were identified to design a new soil
liner system. In the process of
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M. Mukri, N. N. S.Aziz and N. Khalid
http://www.iaeme.com/IJCIET/index.asp 1967 [email protected]
developing models, there are some parameters that were used
based on the physical and
engineering properties of the soil. For example energy of
compaction (E), plasticity index
(PI), plastic limit (PL), liquid limit (LL) optimum moisture
content (OMC), maximum dry
density (MDD), clay content (C), initial saturation (Si) and
percentage of geopolymer (%
Geo). The parameter that has a strong relationship and can
effect hydraulic conductivity of
soil were chosen. All hypothesis leading to the relationships of
the statistical simulation must
be defined clearly before running the test. The values of k ,
R2, P and T shows a good
relationship with the parameter that was used. The results of
all samples were analyzed and an
extensive research had been carried out to improve landfill
system through the establishment
of new soil liner. The test was done on the compacted remolded
soil and the experiment was
conducted in regards to the objectives of this research.
3. RESULTS AND DISCUSSION
3.1. Soil Physical Properties
It is important to determine the percentage of different
particle sizes in a soil in order to
identify the characteristics of the soil. From the sieve
analysis test, the laterite soil used in this
research consisted of about 25.98% of gravel, 35.55% of sand and
38.47% of fine size grain.
Therefore, this laterite soil was classified under very silty
SAND. The average percentage of
liquid limit (LL) for these three samples was 57.28%. Meanwhile,
their average percentages
of plastic limit (PL) and plasticity index (PI) were 52.46% and
4.82% respectively. Based on
the results, the laterite soil examined in this study had a
slightly plastic soil characteristic
because its plasticity index (PI) value was in a range of 3% to
15%. The specific gravity value
for this residual soil fell within the range specified by
previous researchers which were 2.59.
On the other hand, the specific gravity test for soil mix with
geopolymer also had been
determined which are within 2.60-2.66. Different percentage of
geopolymer with soil were
tested which were 5% geopolymer, 10% geopolymer, 15% geopolymer
and 20% geopolymer.
The plain laterite soil produced a pH of 4.44 and followed at
10.24, 10.95, 11.69 and 11.83
for 5%, 10%, 15% and 20% of geopolymer, respectively. For
natural laterite soil, the average
shrinkage of the soil was taken as 7.38% as it was reduced to
4.05%, 3.34%, 2.86% and
2.14% as it had been added with 5% geopolymer, 10% geopolymer,
15% geopolymer and
20% of geopolymer.
3.2. Engineering Properties
The results for standard Proctor compaction test of plain
laterite soil show the optimum
moisture content (OMC) of the soil had a range between 17% to
35% and maximum dry
density (MDD) range between 1.3 Mg/m3 to 1.7 Mg/m3 respectively.
Table 1 showed the
range value of MDD and OMC for Reduced British Standard Level
(RBSL) test, British
Standard Level (BSL)test and British Standard Heavy (BSH) test
with different percentage of
geopolymer
Table 1 Compaction results for RBSL test, BSL test and BSH test
for appearance of 0-20% geopolymer
Compaction Energy
Maximum Dry
Density, MDD
(Mg/m3)
Optimum
Moisture Content,
OMC (%)
Reduced British Standard Level (RBSL) 1.71-1.86 15.40-11.36
British Standard Light (BSL) 1.74-1.85 15.16-13.87
British Standard Heavy (BSH) 1.92-2.02 12.87-11.38
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Geopolymer Effect in Modelling Hydraulic Conductivity for
Designing Soil Liner of Laterite Soil
http://www.iaeme.com/IJCIET/index.asp 1968 [email protected]
3.3. Hydraulic Conductivity
Hydraulic conductivity, k test was carried out for plain
laterite soil and soil with different
percentage of geopolymer. This test was important to determine
the ease of water to pass
through the particle of the soil. Performing laboratory test was
very time-consuming
especially in the case of permeability tests on samples with
high portions of fine particles
content. For example, in this study, one sample took four (4)
months to be fully saturated for
the use of the permeability test. Because of this difficulty and
to save more time, the test was
only carried out for British Standard Light (BSL) test.
Meanwhile, for Reduced British
Standard Level (RBSL) test and British Standard Heavy (BSH)
test, the value of hydraulic
conductivity, k was predicted using the suitable empirical model
developed from previous
studies which are Benson and Trast [6] model. Based on the
results of hydraulic conductivity,
k using this model, it displayed a small amount of difference
when compared with results
from laboratory test. The graph was shown in Figure 3 exhibited
a small difference between
Benson and Trast model with the laboratory results. Because of
such minor difference, this
model was the best estimator among the studied equations to
predict the hydraulic
conductivity for soil samples that compacted with Reduced
British Standard Level (RBSL)
and British Standard Heavy (BSH) condition.
Figure 3 Comparison of hydraulic conductivity, k of laterite
soil with different percentage of
geopolymer and different compaction energy based on empirical
formula from Benson and Trast, [6]
The hydraulic conductivity, k test also had been carried out to
plain laterite soil mix with
different percentage of geopolymer (5%, 10%, 15% and 20%). The
samples of soil were
prepared and molded based on optimum moisture content (OMC)
value from British Standard
Light (BSL) test. From the results, the hydraulic conductivity,
k of plain laterite soil mix with
different percentage of geopolymer decreased nonlinearly with
the addition of geopolymer. It
indicated the soil mix with 15% of geopolymer gave the low
reading of hydraulic
conductivity,k and followed by 10%, 20% and 5% of geopolymer for
Reduced British
Standard Level (RBSL) test and British Standard Light (BSL)
test. Meanwhile, for British
Standard Heavy (BSH) test, it had shown slightly different
results in which the smallest value
of hydraulic conductivity, k was 15% of geopolymer and followed
with 10%, 5% and 20% of
geopolymer.
From the results, the soil samples were compacted using the
British Standard Light (BSL)
compaction energy, yielded hydraulic conductivity, k 1.96
x10-9
m/s to 3.69 x10-10
m/s. In
-
M. Mukri, N. N. S.Aziz and N. Khalid
http://www.iaeme.com/IJCIET/index.asp 1969 [email protected]
order to predict the hydraulic conductivity, k of the sample for
Reduced British Standard
Level (RBSL) test and British Standard Heavy (BSH) test, Benson
and Trast empirical model
was selected because of the results from the laboratory for
British Standard Light (BSL)
exhibit the closer value of hydraulic conductivity, k . The
other empirical model from
previous studies did not fit well with the value from laboratory
test. Referring the models by
Benson and Trast [6] the soil samples compacted with Reduced
British Standard Level
(RBSL) compaction energy contributed hydraulic conductivity, k
value ranging from 8.28 x
10-9
m/s to 8.69 x 10-10
m/s while the soil samples compacted with British Standard
Heavy
(BSH) compaction energy, gave lower hydraulic conductivity, k
ranging from 1.17 x 10-9
m/s
to 1.33 x 10-10
m/s. It can be said that the hydraulic conductivity of soil was
decreased with
increasing percentage of geopolymer. The results are based on
the immediate mixture which
is the sample does not expose to the curing period. It is
believed that when the soil sample
was allowed to cure for a few days, it will produce the better
results of hydraulic conductivity
as compared to results of the immediate mixture.
According to Benson and Trast [6], the effectiveness of liners
and covers for waste
containment was often measured in terms of the possibility of
achieving hydraulic
conductivity ≤ 1 x 10-9
m/s. In general, based on the results of this study, the
hydraulic
conductivity of the soil samples decreased with an increase in
the certain percentages of
geopolymer. The similar observation had been carried out by
previous studies [33, 40]. They
observed a decrease in hydraulic conductivity due to the
precipitation of new minerals as a
result of chemical interactions between additive and soil. The
results of their findings also
suggested the pozzolanic and self-cementing properties of fly
ash have resulted in the
formation of hydration products that could possibly block void
spaces and reduced the
interconnection between fly ash particles. It could be said that
geopolymer was a material that
is able to fill in the gaps between the soil particles and could
ensure low hydraulic
conductivity, k of soil. Table 2, Table 3 and Figure 4presented
the results of hydraulic
conductivity, k from this study.
Table 2 Summary results of hydraulic conductivity (After Benson
and Trast, 1995) for Reduced
British Standard Level (RBSL), British Standard Light (BSL) and
British Standard Heavy (BSH) test.
Compaction
Energy
Hydraulic Conductivity, k (m/s)
0% of
Geopolymer
5% of
Geopolymer
10% of
Geopolymer
15% of
Geopolymer
20% of
Geopolymer
RBSL
BSL
BSH
8.46 x 10-9
2.34 x 10-9
1.33 x 10-9
8.47 x 10-10
3.31 x 10-10
1.31 x 10-10
8.44 x 10-10
3.24 x 10-10
1.29 x 10-10
8.28 x 10-10
3.73 x 10-10
1.17 x 10-10
8.44x 10-10
3.26 x 10-10
1.32 x 10-10
Table 3 Summary results of hydraulic conductivity based on
falling head permeability test for British
Standard Light (BSL) test
Compaction
Energy
Hydraulic Conductivity, k (m/s)
0% of
Geopolymer
5% of
Geopolymer
10% of
Geopolymer
15% of
Geopolymer
20% of
Geopolymer
K labOMC
(-5%)-BSL 3.22 x 10
-9 3.45 x 10
-10 3.10 x 10
-10 3.02 x 10
-10 3.11x 10
-10
K labOMC
-BSL 1.96 x 10
-9 3.46 x 10
-10 3.39 x 10
-10 3.22 x 10
-10 3.42 x 10
-10
K labOMC
(+5%)-BSL 2.98 x 10
-9 3.06 x 10
-10 3.01 x 10
-10 3.28 x 10
-10 3.21 x 10
-10
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Geopolymer Effect in Modelling Hydraulic Conductivity for
Designing Soil Liner of Laterite Soil
http://www.iaeme.com/IJCIET/index.asp 1970 [email protected]
Figure 4 Hydraulic conductivity, k of laterite soil with
different percentage of geopolymer based on
Benson and Trast [6] empirical formula and falling head test
3.2. Modelling of Hydraulic Conductivity with Various
Variables
The suitable parameter such as energy of compaction (E),
percentage of geopolymer,
plasticity index (PI), plastic limit (PL), liquid limit (LL),
percentage of clay (C), optimum
moisture content (OMC), maximum dry density (MDD) and initial
saturation (Si) were chosen
to be used for producing new empirical formula in determining
hydraulic conductivity of soil.
This study successfully produces eight (4) empirical formula to
determine the hydraulic
conductivity of laterite soil with geopolymer. This equations
produces a high regression
coefficient, R2 which is 99.7% [41]. The best equations is;
* (
)+
(1)
Table 4 Empirical formula from this study with percentage of
geopolymer
Variables Empirical Formula Equation
E, OMC, LL
and % Geo
(
) 4
E, Si, PL and
% Geo
(
)
3
E, OMC, LL,
MDD and %
Geo
*
(
) +
2
E, OMC, LL
MDD, C and %
Geo
*(
)(
)+
1
Meanwhile, the other equations that also can be used to
determine the hydraulic
conductivity of soil with % geopolimer are tabulated in Table 4.
Other equations, 2,3 and 4
-
M. Mukri, N. N. S.Aziz and N. Khalid
http://www.iaeme.com/IJCIET/index.asp 1971 [email protected]
are successfully developed and can be used in order to predict
hydraulic conductivity of
laterite soil with geopolymer depends on what parameter that
available.
From the developed models, it is show that the values of T, P
and R2 shows the good
relationship with the parameters that were used which are liquid
limit (LL), plastic limit (PL),
plasticity index (PI), percentage of clay (%C), percentage of
geopolymer (% Geo), optimum
moisture content (OMC) and maximum dry density (MDD).
4. CONCLUSIONS
The results that were obtained from the preliminary and main
laboratory tests enable to
provide a satisfactory prediction of physical and engineering
properties of the laterite soil with
different percentage of geopolymer. This will also enhance the
knowledge and understanding
of the behavior of additive which is geopolymer on how it reacts
with laterite soil and its
effects on the permeability of laterite soil. The hydraulic
conductivity of soil also affected
when geopolymer is mix with soil. The results revealed that the
geopolymer helps reduced the
hydraulic conductivity of plain laterite soil. The hydraulic
conductivity of plain laterite soil
compacted with British Standard Light (BSL) test gives a lower
value of hydraulic
conductivity when geopolymer was added to the soil. At 5%, 10%
and 15% of geopolymer,
the hydraulic conductivity of soil were decreased to 3.46
x10-10
m/s and followed with 3.39
x10-9
m/s and 3.22 x10-10
m/s. When 20% of geopolymer was mixed with soil, the
hydraulic
conductivity of soil shows a little increment which is
3.42x10-10
m/s. Comparing the results
from permeability laboratory test of British Standard Light
(BSL) effort, it is present that the
value of hydraulic conductivity of samples is more accurate with
the empirical model by
Benson and Trast, 1995. Therefore, the empirical model from
Benson and Trast, (1995) was
chosen to predict the value of hydraulic conductivity for
Reduced British Standard Level
(RBSL) and British Standard Heavy (BSH) of soil samples. Based
on the results, it is seen
that the hydraulic conductivity of plain laterite soil compacted
with Reduced British Standard
Level (RBSL), British Standard Level (BSL) and British Standard
Heavy (BSH) did not meet
the requirement in designing a soil liner. However, after 5%,
10%, 15% and 20% of
geopolymer were mixed with all soil samples, the range value of
hydraulic conductivity of
soil between 3.46 x10-10
m/s to 3.22 x10-10
m/s which are less than 1 x10-9
m/s as a requirement
in designing a soil liner. Besides that, the new empirical
formula was developed in order to
determine the hydraulic conductivity of laterite soil in
designing a compacted soil liner. The
formula can be used directly to determine the hydraulic
conductivity of laterite soil by
entering the suitable parameter without the need to conduct the
permeability test. This study
successfully produces eight (8) empirical formula to determine
the hydraulic conductivity of
laterite soil without and with geopolymer. All of these
equations produces a high regression
coefficient, R2 which are 98.8% and 99.7%. In a nutshell, it can
be said that the developed
models in this study are able to provide a good prediction of
hydraulic conductivity, k for
laterite soil and laterite soil mixed with a different
percentage of geopolymer. On the other
hand, the used of additive which is geopolymer are economically
advantage and environment-
friendly compared to another additive such as bentonite, lime,
and extra. Last but not least, it
is hoped that the results of this study can be used as a
guideline in designing a soil liner
system at landfill area.
ACK NOWLEDGEMENTS
The authors thank to all staff in the Faculty of Civil
Engineering, UiTM for permission and
encouragement to conduct such studies for the benefit of science
and society. The authors
would like to acknowledge that this research has been carried
out funded by Universiti
-
Geopolymer Effect in Modelling Hydraulic Conductivity for
Designing Soil Liner of Laterite Soil
http://www.iaeme.com/IJCIET/index.asp 1972 [email protected]
Teknologi MARA (UiTM), Institute of Quality and Knowledge
Advancement (InQKA) and
support from Faculty of Civil Engineering, Universiti Teknologi
MARA (UiTM).
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