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Proceedings of Indian Geotechnical Conference
December 22-24, 2013, Roorkee
INFLUENCE OF GEOPOLYMER ON THE STRENGTH CHARACTERSTICS
OF SAND MIXED SOFT MARINE CLAY
R. Dayakar Babu*, Prof. of Civil Engg, KITS- Divili, E.G Dist.,-533443, [email protected]
K. Ramu, Professor of Civil Engineering, UCEK, JNTUK, Kakinada-533003, [email protected]
S. Durga Prasad, Sr. Engineer. (Projects), M/S IVRCL Limited, HYD, [email protected]
K. Ashok Kumar, AEN (Civil), SC Railway, Vijayawada division, [email protected]
ABSTRACT: Soft marine clays, which occur in huge quantities, need improvement by stabilization or by
replacing them with granular material. The replacement results in both disposal and environmental problems.
Hence an attempt was made to investigate the strength characteristics of soft marine clay and sand mixes treated
with various percentages of geopolymer, a term coined representing a broad range of materials characterized by
chains or networks of inorganic molecules. The present paper reveals that the inclusion of different percentages of
geopolymer to the blends of soft clay and sand had certainly improved the strength parameters and also proved that
geopolymer stabilization was effective.
INTRODUCTION
India has large coastline exceeding 6000kms and
many of these areas are covered with thick soft
marine clay deposits with very low shear strength
and high compressibility. In view of the coastal
area developments in the recent past, large number
of ports and industries are being brought up. In
addition, the availability of land for the
development of commercial, domestic, industrial
transportation, and infrastructure etc. are scarce
particularly in urban areas. For foundation of any
structure in soft clay grounds, necessary
stabilization or ground improvement is necessary
by replacing the soft clay deposit with granular
material. While replacing the soft clay deposit with
superior quality material, occurring in huge soft
clay deposits, resulting land occupation and
environmental problems.
Apart from the above, the amount of solid wastes
has increased year by year and its disposal became
a serious problem. Many of these wastes such as
Fly-Ash, Blast Furnace Slag, Rice Husk Ash,
Marble Sludge Powder etc., are suspended
particulate matters which are most harmful to
human health. Hence, the soft clay deposits with
industrial wastes should be properly treated and
utilized to avoid the various effects on human
beings. Out of several techniques available for
improving the shear strength, this paper aims at
probing the efficacy of Geopolymer, a relatively
new eco-friendly binder material in improving the
Strength Characteristics of Soft Clay and Sand
Mixes.
LITERATURE REVIEW
Soft clay can be categorized as problematic soil.
The low strength and high compressibility
characteristics of this soil are the major reasons,
why a careful design analysis could be taken for
any structure to be built on it. Ground
improvement is required to prevent these problems
to the structures built in areas having thick deposits
of soft clay.
The soft clays have low bearing capacities and
suffer from large settlements when loaded.
Ground improvement is required to prevent these
excessive settlements of the structures built in
areas. The construction of highway and railway
embankments on normally consolidated soft soil
deposits has been affected by the excessive
differential settlements, lateral displacements in
the absence of an appropriate ground
improvement prior to construction. To prevent the
unfavourable conditions, the application of
preloading with prefabricated vertical drains
(PVDs) prior to the construction ha
Page 1 of 6
R.Dayakar Babu, K.Ramu, S.Durga Prasad & K. Ashok Kumar.
popularly employed in many large scale projects
[1,2]. The gained shear strength of the foundation
can be achieved due to rapid excess pore pressure
dissipation. It is also well-known that the high
outward lateral movement causing the
embankment instability can also be reduced.
Origin and Typical Characteristics and
Properties of Soft Clay
Soil may also be separated into three very broad
categories which are cohesion less, cohesive and
organic soil. Cohesion less soils are gravel, sand
and silt. This type of soil particles do not tend to
stick together. Organic soil is described as soil
containing a sufficient amount of organic matter to
affect its engineering properties. Cohesive soils are
characterized by very small particle size where
surface chemical attractions are predominant and in
other words, the particles tend to stick to others.
The need of development in India has forced to
study the soft clay behaviour, where in the majority
of soft clay deposits existing are marine soft clays.
Hence, a very detailed soil investigation need to be
done and deep understanding of behaviour soft
clay soil is important and crucial.
Problems Associated with Soft Clay
The major problems of the soft clay are the
stability and the settlement. These soils are
compressible and could undergo volume changes
when they are subjected to load from structures.
The high compressibility properties of soft clay are
one of the major factors that could lead to high
settlements. This is happened from the fact that
soft clay are finer in particles and being too
cohesive with the presence of water. Water could
be the main agent that makes the soil, become
unstable especially with the high ability of the soft
clay soil to trap huge amount water within its
particles. However, some measures could be taken
to overcome the problem [3], such as
a) Deep foundations could be driven through the
unsuitable soils thereby avoiding them altogether.
b) Excavate and replace the soft soils with suitable
soils.
c) Stabilize the soft soils with injected additives.
Stabilisation of Soft Clay
Lime Stabilisation
Lime stabilization is most commonly used in road
sub grades to improve its strength but it can be
used for small buildings. It involves the mixing of
lime and soil by the use of a large profiler. The
mixing depth is usually limited to approximately
600mm and the lime is typically mixed at 3% to
6% although this can change depending on the
particular situation. The use of lime in the clay can
increase the CBR (California Bearing Ratio) from
values of approximately 2%up to 8% [4].
Cement Stabilisation
Adding cement to the soil has a similar effect to
adding lime as it helps decrease the liquid limit and
increase the plasticity index. The cement is usually
added to the soil at approximately 10% by weight.
When cement is hydrating satisfactorily in a
mixture an increase in strength is obtained with
increasing cement content. Clayey soils require
more quantity of cement than sandy soils.
Chemical Stabilisation
It consists of bonding of clayey soil particles with a
cementing agent; the primary additive is chemical
that is produced by chemical reaction with soil,
thus changes clay particles composition by
electrolyte forces or by chemical reaction. Asphalt
petroleum emulsions - Non-water soluble organic
compounds that are “emulsified” or suspended in
water. When these emulsions are sprayed onto soil,
they stick to each other, and eventually harden to
form a solid mass.
Geopolymer
Geopolymer materials represent an innovative
technology that is generating considerable interest
in the construction industry. In contrast to portland
cement, most geopolymer systems rely on
industrial by products to provide the binding
agents. Since portland cement is responsible for
upward of 85% of the energy and 90% of the
carbon dioxide attributed to a typical ready-mixed
concrete, the potential energy and carbon dioxide
savings through the use of geopolymer can be
considerable. Consequently, there is growing
Page 2 of 6
Influence of geopolymer on the strength characteristics of sand mixed soft marine clay
interest
in
geopolymer
applications
in
geopolymer technology is considered new, the
technology has ancient roots and has been
postulated as the building material used in the
construction of the pyramids at Giza as well as in
other ancient construction [5,6 & 7]. Moreover,
alkali-activated slag cement is a type of
geopolymer that has been in use since the mid-20th
century.
What is Geopolymer?
The term geopolymer was coined by Davidovits in
1978 to represent a broad range of materials
characterized by chains or networks of inorganic
molecules. Geopolymer rely on thermally activated
natural materials (e.g., kaolinite clay) or industrial
by products (e.g., fly ash or slag) to provide a
source of Silicon (Si) and Aluminum (Al), which is
dissolved in an alkaline activating solution and
subsequently polymerizes into molecular chains
and networks to create the hardened binder. The
ultimate structure of the geopolymer depends
largely on the ratio of Si to Al (Si:Al), with the
materials most often considered for use in
transportation infrastructure typically having an
Si:Al between 2 and 3.5 [7].
Existing applications of Geopolymer
To date, there are no widespread applications of
geopolymer concrete in transportation infrastructure, although the technology is rapidly advancing
in Europe and Australia. One North American
geopolymer application is a blended portlandgeopolymer cement known as Pyrament® (patented in 1984), variations of which continue to be
successfully used for rapid pavement repair. Other
portland-geopolymer cement systems may soon
emerge. In addition to Pyrament®, the U.S.
military is using geopolymer pavement coatings
designed to resist the heat generated by vertical
takeoff and landing aircraft [8]. In the short term,
there is potential for geopolymer applications for
bridges, such as precast structural elements and
decks as well as structural retrofits using
geopolymer-fiber composites.
Rice Husk Ash
Rice milling generates a by product know as husk.
This surrounds the paddy grain. During milling of
transportation
infrastructure.
Although
paddy about 78 % of weight is received as rice,
broken rice and bran. Rest 22 % of the weight of
paddy is received as husk. This husk is used as fuel
in the rice mills to generate steam for the
parboiling process. This husk contains about 75 %
organic volatile matter and the balance 25 % of the
weight of this husk is converted into ash during the
firing process, is known as rice husk ash (RHA).
This RHA in turn contains around 85 % - 90 %
amorphous silica. Disposal of rice husk ash is an
important issue in the countries which cultivate
large quantities of rice. More than 100 million tons
of rice husk produced globally begins to impact the
environment if not disposed of properly. As the
production rate of rice husk ash is about 20% of the
dried rice husk, the amount of RHA generated
yearly is about 20 million tons worldwide [9].
EXPERIMENTAL PROGRAM
Materials Used
Soft Clay
The soft clay used in the laboratory
experimentation was collected from Yetimoga,
Kakinada, East Godavari Dist. This soil classified
as clay of high compressibility (CH) according to
I.S classification and the prosperities described
below.
Table 1 Physical properties of Soft Clay
Property
Grain size analysis
Sand
Silt
Clay
Atterberg’s limits
Liquid Limit
Plastic Limit
Plasticity Index
Compaction parameters
OMC
MDD
Value
9%
27%
64%
78%
32%
46%
29%
1.5 gm/cc
Sand
The locally available sand was collected form
Godavari River and conducted proctor compaction
Page 3 of 6
R.Dayakar Babu, K.Ramu, S.Durga Prasad & K. Ashok Kumar.
test, which revealed that its Maximum Dry Density
and Optimum Moisture Content were 1.78 g/cc and
15.76% respectively.
Geopolymer (Rice Husk Ash based)
Geopolymer can be produced by the polymeric
reaction of alkaline liquids with the silicon and
aluminium in the source material of geological
origin or by product materials such as fly ash and
rice husk ash. The most common alkaline liquid
used in the geo polymerisation is a combination of
Sodium Hydroxide (NaOH) or Potassium
Hydroxide (KOH) and Sodium Silicate or
Potassium Silicate. The sodium hydroxide solution
was prepared by dissolving either the flakes or
pellets in water. This solution comprises of 25.2%
of NaOH solids (Commercially available in flakes /
pellets form) and 74.8 % of water to make a
solution with concentration of 8 molar.
The
Sodium silicate solution A53 was commercially
available with SiO2 to Na2O ratio by mass of
approximately 2. i.e. Na2O=14.7%, SiO2=29.4%
and Water = 55.9% by mass.
Mould for Preparation of Specimen
To prepare 100mm diameter and 200mm high
specimen to conduct triaxial shear test, the mould
was designed with mild steel, so that it can be split
in to two parts after the sample was prepared.
Fig. 1 Sample Preparation Mould (100mm dia &
200mm height)
Variables studied
Sand was mixed to soft clay of varying percentage
combinations to study the strength behaviour at
different percentages geopolymer as additive. The
table 2 describes the percentage combinations of
soft clay, sand and geopolymer.
Sample Preparation
The samples for the shear test were prepared by
mixing soft clay with different percentages of sand.
Geopolymer was mixed to the soil – sand blend.
The well blended material was compacted to 98%
of OMC & MDD in the 100mm diameter and
200mm high mould in five layers. 3 specimens for
each combination were prepared and kept for
07days curing.
Tests Conducted
To assess the efficacy of geopolymer on the Shear
Strength parameters of sand blended soft soil,
Triaxial Shear Tests in the laboratory are
conducted as per I.S: 2720 (Part-XII)-1981.
Table 2 Different combinations of soft clay, sand
and Geopolymer used in the laboratory studies.
Trial No Soft Clay
1
100%
2
100%
3
100%
4
100%
5
75%
6
75%
7
75%
8
75%
9
50%
10
50%
11
50%
12
50%
13
25%
14
25%
15
25%
16
25%
17
0%
18
0%
19
0%
20
0%
Sand
0%
0%
0%
0%
25%
25%
25%
25%
50%
50%
50%
50%
75%
75%
75%
75%
100%
100%
100%
100%
Geopolymer
0%
5%
10%
15%
0%
5%
10%
15%
0%
5%
10%
15%
0%
5%
10%
15%
0%
5%
10%
15%
RESULTS & DISCUSSIONS
The results of variation in strength parameters of
soft clay i.e. cohesion (c) and angle of internal
friction (Ø) by adding different percentages of
geopolymer to soft clay and sand blends are
presented and discussed below.
Page 4 of 6
Influence of geopolymer on the strength characteristics of sand mixed soft marine clay
Influence of
Different
Percentages
of
Geopolymer on the Cohesion (C) of Soft Clay
and Sand Blends
Figure 2 shows the variation in cohesion(C) by
mixing different percentages of geopolymer to soft
clay and sand blends for the soil samples prepared
at MDD and OMC. It is observed that the increase
in cohesion from 14.22 kPa to 23.54 kPa for 100%
soft clay which is an improvement of 66% with an
increase in geopolymer from 0% to 15%. Further it
can be observed that an improvement of 113 % for
75% soft clay and 25% sand blend, an
improvement of 109 % for the 50% soft clay
and50% sand blend and an improvement of 87%
for the 25% soft clay and 75% sand blend. The
cohesion of sand increases to 19.62 kPa with an
increase in geopolymer from 0% to 15% in the
Geopolymer and mix.
geopolymer. For the soft clay with increase in
increase in percentage of geopolymer from 0 to
15% the angle of internal friction increases
marginally from 2 to 3. Further it can be observed
that the improvement in angle of internal friction
(Φ) as 100% for the 75% soft clay & 25% sand
blend, an improvement of 233% for the 50% soft
clay & 50% sand blend, an improvement of 167%
for the 25% soft clay & 75% sand blend and an
improvement of 3% for the 100% sand with the
increase in percentages of geopolymer from 0% to
15%. There is a nominal improvement in angle of
internal friction, (Φ) with the increase in sand from
0% to 75% for the different mix proportions of
geopolymer. It can also be seen that the trend of
variation in angle of internal Friction, (Φ) is very
much similar for the soft clay and sand blends for
all the percentages of geopolymer i.e., 0%, 5%,
10% and 15%.
Hence, from the above discussions, it is clear that
the waste soft soil which is to be disposed off,
causing severe environmental problem can be
effectively utilized by blending (replacement) it
with locally available sand (granular material) and
stabilizing the blended soil with an eco-friendly
binder, Geopolymer and also the efficacy of
geopolymer was established.
Fig. 2 Variation in Cohesion (C) for different
blends of soft clay and sand w.r.t. different
percentages of geopolymer.
Influence
of
different
percentages
of
geopolymer on the Angle of Internal Friction
(Φ) of soft clay and sand blends
The variation in Angle of Internal Friction (Φ) with
the different percentages of geopolymer mixed
with soft clay and sand blends is shown in Fig. 3.
All the soil samples are prepared at MDD and
OMC. From the figure, it can be observed that the
angle of internal friction is increasing with the
Fig. 3 Variation of Angle of Internal Friction (φ)
for different blends of soft clay and sand w.r.t.
different percentages of geopolymer.
Page 5 of 6
R.Dayakar Babu, K.Ramu, S.Durga Prasad & K. Ashok Kumar.
CONCLUSIONS
From the detailed analysis of the obtained results
and therein its discussions infer the below said
conclusions.
1) The Cohesion (C) of soft clay and sand blends
had been considerably improved with the
increase in percentage of geopolymer content.
2) The angle of internal friction (φ) of soft clay
and sand blends had been marginally improved
with the increase in percentage of geopolymer.
3) The inclusion of different percentages of
geopolymer to the blends of soft clay and sand
proved to be effective in improving the strength
parameters i.e. Cohesion and Angle of Internal
friction.
4) The same trend was observed to be very much
similar for all the percentages of geopolymer
content i.e., 0%, 5%, 10% and 15% for both
Cohesion and Angle of Internal friction.
5) Finally, the authors conclude that the waste &
weak soft soil can be improved effectively by
replacing locally available granular material and
further stabilizing it with optimum content of
geopolymer.
SCOPE FOR THE FURTHER WORK
The work can be extended by decreasing the sand
proportions to the soft clay and introducing more
curing periods i.e. 14 days, 28 days and 90 days by
blending different percentages of geopolymer to
arrive at the optimum combinations for effective
improvement of the soft clay. This study can be
further extended to various combinations of
geopolymer and by replacing sand with other
industrial by products.
4. Avalle, D L (2007), Ground vibrations during
impact rolling, 10th Australia New Zealand
Conference on Geomechanics (2007), Carillon
Conference Management for the Australian
Geomechanics Society, Australia(Stabilised
Pavements Australia, 2006).
5. Davidovits, J. 1984. "Pyramids of Egypt Made
of Man-Made Stone, Myth or Fact?"
Symposium
on
Archaeometry
1984.
Smithsonian Institution, Washington, DC
6. Barsoum, M. W., and A. Ganguly. 2006.
"Microstructural Evidence of Reconstituted
Limestone Blocks in the Great Pyramids of
Egypt." Journal of the American Ceramics
Society, 89. Wiley-Blackwell, Malden, MA.
7. Davidovits, J. 2008. Geopolymer Chemistry
and Applications. Institut Géopolymère, SaintQuentin, France
8. Hambling, D. 2009. "Cool Under Pressure:
Geopolymers Offer Diverse Structural
Benefits." Defense Technology International,
Washington, DC
9. Nagrale, S.D., Dr. Hemant Hajare and Pankaj
R. Modak(2012), Utilization Of Rice Husk
Ash, International Journal of Engineering
Research and Applications (IJERA),Vol. 2,
pp.001-005.
REFERENCES
1. Hansbo, S. (1979), Consolidation of clay by
band shaped prefabricated drains Ground
Eng'g., Vol. 12, No. 5.
2. Indraratna, B. and Redana, I W. (2000),
Behaviour of Vertical Drains in Soft Clay with
Smear and Well Resistance, Canadian
Geotechnical Journal, Vol 37.
3. Schaefer, V.R., (1997), Ground Improvement,
Ground Reinforcement, Ground Treatment
Developments
1987-1997,
Geotechnical
special publication No.69, ASCE, Logan, UT.
Page 6 of 6
December 22-24, 2013, Roorkee
INFLUENCE OF GEOPOLYMER ON THE STRENGTH CHARACTERSTICS
OF SAND MIXED SOFT MARINE CLAY
R. Dayakar Babu*, Prof. of Civil Engg, KITS- Divili, E.G Dist.,-533443, [email protected]
K. Ramu, Professor of Civil Engineering, UCEK, JNTUK, Kakinada-533003, [email protected]
S. Durga Prasad, Sr. Engineer. (Projects), M/S IVRCL Limited, HYD, [email protected]
K. Ashok Kumar, AEN (Civil), SC Railway, Vijayawada division, [email protected]
ABSTRACT: Soft marine clays, which occur in huge quantities, need improvement by stabilization or by
replacing them with granular material. The replacement results in both disposal and environmental problems.
Hence an attempt was made to investigate the strength characteristics of soft marine clay and sand mixes treated
with various percentages of geopolymer, a term coined representing a broad range of materials characterized by
chains or networks of inorganic molecules. The present paper reveals that the inclusion of different percentages of
geopolymer to the blends of soft clay and sand had certainly improved the strength parameters and also proved that
geopolymer stabilization was effective.
INTRODUCTION
India has large coastline exceeding 6000kms and
many of these areas are covered with thick soft
marine clay deposits with very low shear strength
and high compressibility. In view of the coastal
area developments in the recent past, large number
of ports and industries are being brought up. In
addition, the availability of land for the
development of commercial, domestic, industrial
transportation, and infrastructure etc. are scarce
particularly in urban areas. For foundation of any
structure in soft clay grounds, necessary
stabilization or ground improvement is necessary
by replacing the soft clay deposit with granular
material. While replacing the soft clay deposit with
superior quality material, occurring in huge soft
clay deposits, resulting land occupation and
environmental problems.
Apart from the above, the amount of solid wastes
has increased year by year and its disposal became
a serious problem. Many of these wastes such as
Fly-Ash, Blast Furnace Slag, Rice Husk Ash,
Marble Sludge Powder etc., are suspended
particulate matters which are most harmful to
human health. Hence, the soft clay deposits with
industrial wastes should be properly treated and
utilized to avoid the various effects on human
beings. Out of several techniques available for
improving the shear strength, this paper aims at
probing the efficacy of Geopolymer, a relatively
new eco-friendly binder material in improving the
Strength Characteristics of Soft Clay and Sand
Mixes.
LITERATURE REVIEW
Soft clay can be categorized as problematic soil.
The low strength and high compressibility
characteristics of this soil are the major reasons,
why a careful design analysis could be taken for
any structure to be built on it. Ground
improvement is required to prevent these problems
to the structures built in areas having thick deposits
of soft clay.
The soft clays have low bearing capacities and
suffer from large settlements when loaded.
Ground improvement is required to prevent these
excessive settlements of the structures built in
areas. The construction of highway and railway
embankments on normally consolidated soft soil
deposits has been affected by the excessive
differential settlements, lateral displacements in
the absence of an appropriate ground
improvement prior to construction. To prevent the
unfavourable conditions, the application of
preloading with prefabricated vertical drains
(PVDs) prior to the construction ha
Page 1 of 6
R.Dayakar Babu, K.Ramu, S.Durga Prasad & K. Ashok Kumar.
popularly employed in many large scale projects
[1,2]. The gained shear strength of the foundation
can be achieved due to rapid excess pore pressure
dissipation. It is also well-known that the high
outward lateral movement causing the
embankment instability can also be reduced.
Origin and Typical Characteristics and
Properties of Soft Clay
Soil may also be separated into three very broad
categories which are cohesion less, cohesive and
organic soil. Cohesion less soils are gravel, sand
and silt. This type of soil particles do not tend to
stick together. Organic soil is described as soil
containing a sufficient amount of organic matter to
affect its engineering properties. Cohesive soils are
characterized by very small particle size where
surface chemical attractions are predominant and in
other words, the particles tend to stick to others.
The need of development in India has forced to
study the soft clay behaviour, where in the majority
of soft clay deposits existing are marine soft clays.
Hence, a very detailed soil investigation need to be
done and deep understanding of behaviour soft
clay soil is important and crucial.
Problems Associated with Soft Clay
The major problems of the soft clay are the
stability and the settlement. These soils are
compressible and could undergo volume changes
when they are subjected to load from structures.
The high compressibility properties of soft clay are
one of the major factors that could lead to high
settlements. This is happened from the fact that
soft clay are finer in particles and being too
cohesive with the presence of water. Water could
be the main agent that makes the soil, become
unstable especially with the high ability of the soft
clay soil to trap huge amount water within its
particles. However, some measures could be taken
to overcome the problem [3], such as
a) Deep foundations could be driven through the
unsuitable soils thereby avoiding them altogether.
b) Excavate and replace the soft soils with suitable
soils.
c) Stabilize the soft soils with injected additives.
Stabilisation of Soft Clay
Lime Stabilisation
Lime stabilization is most commonly used in road
sub grades to improve its strength but it can be
used for small buildings. It involves the mixing of
lime and soil by the use of a large profiler. The
mixing depth is usually limited to approximately
600mm and the lime is typically mixed at 3% to
6% although this can change depending on the
particular situation. The use of lime in the clay can
increase the CBR (California Bearing Ratio) from
values of approximately 2%up to 8% [4].
Cement Stabilisation
Adding cement to the soil has a similar effect to
adding lime as it helps decrease the liquid limit and
increase the plasticity index. The cement is usually
added to the soil at approximately 10% by weight.
When cement is hydrating satisfactorily in a
mixture an increase in strength is obtained with
increasing cement content. Clayey soils require
more quantity of cement than sandy soils.
Chemical Stabilisation
It consists of bonding of clayey soil particles with a
cementing agent; the primary additive is chemical
that is produced by chemical reaction with soil,
thus changes clay particles composition by
electrolyte forces or by chemical reaction. Asphalt
petroleum emulsions - Non-water soluble organic
compounds that are “emulsified” or suspended in
water. When these emulsions are sprayed onto soil,
they stick to each other, and eventually harden to
form a solid mass.
Geopolymer
Geopolymer materials represent an innovative
technology that is generating considerable interest
in the construction industry. In contrast to portland
cement, most geopolymer systems rely on
industrial by products to provide the binding
agents. Since portland cement is responsible for
upward of 85% of the energy and 90% of the
carbon dioxide attributed to a typical ready-mixed
concrete, the potential energy and carbon dioxide
savings through the use of geopolymer can be
considerable. Consequently, there is growing
Page 2 of 6
Influence of geopolymer on the strength characteristics of sand mixed soft marine clay
interest
in
geopolymer
applications
in
geopolymer technology is considered new, the
technology has ancient roots and has been
postulated as the building material used in the
construction of the pyramids at Giza as well as in
other ancient construction [5,6 & 7]. Moreover,
alkali-activated slag cement is a type of
geopolymer that has been in use since the mid-20th
century.
What is Geopolymer?
The term geopolymer was coined by Davidovits in
1978 to represent a broad range of materials
characterized by chains or networks of inorganic
molecules. Geopolymer rely on thermally activated
natural materials (e.g., kaolinite clay) or industrial
by products (e.g., fly ash or slag) to provide a
source of Silicon (Si) and Aluminum (Al), which is
dissolved in an alkaline activating solution and
subsequently polymerizes into molecular chains
and networks to create the hardened binder. The
ultimate structure of the geopolymer depends
largely on the ratio of Si to Al (Si:Al), with the
materials most often considered for use in
transportation infrastructure typically having an
Si:Al between 2 and 3.5 [7].
Existing applications of Geopolymer
To date, there are no widespread applications of
geopolymer concrete in transportation infrastructure, although the technology is rapidly advancing
in Europe and Australia. One North American
geopolymer application is a blended portlandgeopolymer cement known as Pyrament® (patented in 1984), variations of which continue to be
successfully used for rapid pavement repair. Other
portland-geopolymer cement systems may soon
emerge. In addition to Pyrament®, the U.S.
military is using geopolymer pavement coatings
designed to resist the heat generated by vertical
takeoff and landing aircraft [8]. In the short term,
there is potential for geopolymer applications for
bridges, such as precast structural elements and
decks as well as structural retrofits using
geopolymer-fiber composites.
Rice Husk Ash
Rice milling generates a by product know as husk.
This surrounds the paddy grain. During milling of
transportation
infrastructure.
Although
paddy about 78 % of weight is received as rice,
broken rice and bran. Rest 22 % of the weight of
paddy is received as husk. This husk is used as fuel
in the rice mills to generate steam for the
parboiling process. This husk contains about 75 %
organic volatile matter and the balance 25 % of the
weight of this husk is converted into ash during the
firing process, is known as rice husk ash (RHA).
This RHA in turn contains around 85 % - 90 %
amorphous silica. Disposal of rice husk ash is an
important issue in the countries which cultivate
large quantities of rice. More than 100 million tons
of rice husk produced globally begins to impact the
environment if not disposed of properly. As the
production rate of rice husk ash is about 20% of the
dried rice husk, the amount of RHA generated
yearly is about 20 million tons worldwide [9].
EXPERIMENTAL PROGRAM
Materials Used
Soft Clay
The soft clay used in the laboratory
experimentation was collected from Yetimoga,
Kakinada, East Godavari Dist. This soil classified
as clay of high compressibility (CH) according to
I.S classification and the prosperities described
below.
Table 1 Physical properties of Soft Clay
Property
Grain size analysis
Sand
Silt
Clay
Atterberg’s limits
Liquid Limit
Plastic Limit
Plasticity Index
Compaction parameters
OMC
MDD
Value
9%
27%
64%
78%
32%
46%
29%
1.5 gm/cc
Sand
The locally available sand was collected form
Godavari River and conducted proctor compaction
Page 3 of 6
R.Dayakar Babu, K.Ramu, S.Durga Prasad & K. Ashok Kumar.
test, which revealed that its Maximum Dry Density
and Optimum Moisture Content were 1.78 g/cc and
15.76% respectively.
Geopolymer (Rice Husk Ash based)
Geopolymer can be produced by the polymeric
reaction of alkaline liquids with the silicon and
aluminium in the source material of geological
origin or by product materials such as fly ash and
rice husk ash. The most common alkaline liquid
used in the geo polymerisation is a combination of
Sodium Hydroxide (NaOH) or Potassium
Hydroxide (KOH) and Sodium Silicate or
Potassium Silicate. The sodium hydroxide solution
was prepared by dissolving either the flakes or
pellets in water. This solution comprises of 25.2%
of NaOH solids (Commercially available in flakes /
pellets form) and 74.8 % of water to make a
solution with concentration of 8 molar.
The
Sodium silicate solution A53 was commercially
available with SiO2 to Na2O ratio by mass of
approximately 2. i.e. Na2O=14.7%, SiO2=29.4%
and Water = 55.9% by mass.
Mould for Preparation of Specimen
To prepare 100mm diameter and 200mm high
specimen to conduct triaxial shear test, the mould
was designed with mild steel, so that it can be split
in to two parts after the sample was prepared.
Fig. 1 Sample Preparation Mould (100mm dia &
200mm height)
Variables studied
Sand was mixed to soft clay of varying percentage
combinations to study the strength behaviour at
different percentages geopolymer as additive. The
table 2 describes the percentage combinations of
soft clay, sand and geopolymer.
Sample Preparation
The samples for the shear test were prepared by
mixing soft clay with different percentages of sand.
Geopolymer was mixed to the soil – sand blend.
The well blended material was compacted to 98%
of OMC & MDD in the 100mm diameter and
200mm high mould in five layers. 3 specimens for
each combination were prepared and kept for
07days curing.
Tests Conducted
To assess the efficacy of geopolymer on the Shear
Strength parameters of sand blended soft soil,
Triaxial Shear Tests in the laboratory are
conducted as per I.S: 2720 (Part-XII)-1981.
Table 2 Different combinations of soft clay, sand
and Geopolymer used in the laboratory studies.
Trial No Soft Clay
1
100%
2
100%
3
100%
4
100%
5
75%
6
75%
7
75%
8
75%
9
50%
10
50%
11
50%
12
50%
13
25%
14
25%
15
25%
16
25%
17
0%
18
0%
19
0%
20
0%
Sand
0%
0%
0%
0%
25%
25%
25%
25%
50%
50%
50%
50%
75%
75%
75%
75%
100%
100%
100%
100%
Geopolymer
0%
5%
10%
15%
0%
5%
10%
15%
0%
5%
10%
15%
0%
5%
10%
15%
0%
5%
10%
15%
RESULTS & DISCUSSIONS
The results of variation in strength parameters of
soft clay i.e. cohesion (c) and angle of internal
friction (Ø) by adding different percentages of
geopolymer to soft clay and sand blends are
presented and discussed below.
Page 4 of 6
Influence of geopolymer on the strength characteristics of sand mixed soft marine clay
Influence of
Different
Percentages
of
Geopolymer on the Cohesion (C) of Soft Clay
and Sand Blends
Figure 2 shows the variation in cohesion(C) by
mixing different percentages of geopolymer to soft
clay and sand blends for the soil samples prepared
at MDD and OMC. It is observed that the increase
in cohesion from 14.22 kPa to 23.54 kPa for 100%
soft clay which is an improvement of 66% with an
increase in geopolymer from 0% to 15%. Further it
can be observed that an improvement of 113 % for
75% soft clay and 25% sand blend, an
improvement of 109 % for the 50% soft clay
and50% sand blend and an improvement of 87%
for the 25% soft clay and 75% sand blend. The
cohesion of sand increases to 19.62 kPa with an
increase in geopolymer from 0% to 15% in the
Geopolymer and mix.
geopolymer. For the soft clay with increase in
increase in percentage of geopolymer from 0 to
15% the angle of internal friction increases
marginally from 2 to 3. Further it can be observed
that the improvement in angle of internal friction
(Φ) as 100% for the 75% soft clay & 25% sand
blend, an improvement of 233% for the 50% soft
clay & 50% sand blend, an improvement of 167%
for the 25% soft clay & 75% sand blend and an
improvement of 3% for the 100% sand with the
increase in percentages of geopolymer from 0% to
15%. There is a nominal improvement in angle of
internal friction, (Φ) with the increase in sand from
0% to 75% for the different mix proportions of
geopolymer. It can also be seen that the trend of
variation in angle of internal Friction, (Φ) is very
much similar for the soft clay and sand blends for
all the percentages of geopolymer i.e., 0%, 5%,
10% and 15%.
Hence, from the above discussions, it is clear that
the waste soft soil which is to be disposed off,
causing severe environmental problem can be
effectively utilized by blending (replacement) it
with locally available sand (granular material) and
stabilizing the blended soil with an eco-friendly
binder, Geopolymer and also the efficacy of
geopolymer was established.
Fig. 2 Variation in Cohesion (C) for different
blends of soft clay and sand w.r.t. different
percentages of geopolymer.
Influence
of
different
percentages
of
geopolymer on the Angle of Internal Friction
(Φ) of soft clay and sand blends
The variation in Angle of Internal Friction (Φ) with
the different percentages of geopolymer mixed
with soft clay and sand blends is shown in Fig. 3.
All the soil samples are prepared at MDD and
OMC. From the figure, it can be observed that the
angle of internal friction is increasing with the
Fig. 3 Variation of Angle of Internal Friction (φ)
for different blends of soft clay and sand w.r.t.
different percentages of geopolymer.
Page 5 of 6
R.Dayakar Babu, K.Ramu, S.Durga Prasad & K. Ashok Kumar.
CONCLUSIONS
From the detailed analysis of the obtained results
and therein its discussions infer the below said
conclusions.
1) The Cohesion (C) of soft clay and sand blends
had been considerably improved with the
increase in percentage of geopolymer content.
2) The angle of internal friction (φ) of soft clay
and sand blends had been marginally improved
with the increase in percentage of geopolymer.
3) The inclusion of different percentages of
geopolymer to the blends of soft clay and sand
proved to be effective in improving the strength
parameters i.e. Cohesion and Angle of Internal
friction.
4) The same trend was observed to be very much
similar for all the percentages of geopolymer
content i.e., 0%, 5%, 10% and 15% for both
Cohesion and Angle of Internal friction.
5) Finally, the authors conclude that the waste &
weak soft soil can be improved effectively by
replacing locally available granular material and
further stabilizing it with optimum content of
geopolymer.
SCOPE FOR THE FURTHER WORK
The work can be extended by decreasing the sand
proportions to the soft clay and introducing more
curing periods i.e. 14 days, 28 days and 90 days by
blending different percentages of geopolymer to
arrive at the optimum combinations for effective
improvement of the soft clay. This study can be
further extended to various combinations of
geopolymer and by replacing sand with other
industrial by products.
4. Avalle, D L (2007), Ground vibrations during
impact rolling, 10th Australia New Zealand
Conference on Geomechanics (2007), Carillon
Conference Management for the Australian
Geomechanics Society, Australia(Stabilised
Pavements Australia, 2006).
5. Davidovits, J. 1984. "Pyramids of Egypt Made
of Man-Made Stone, Myth or Fact?"
Symposium
on
Archaeometry
1984.
Smithsonian Institution, Washington, DC
6. Barsoum, M. W., and A. Ganguly. 2006.
"Microstructural Evidence of Reconstituted
Limestone Blocks in the Great Pyramids of
Egypt." Journal of the American Ceramics
Society, 89. Wiley-Blackwell, Malden, MA.
7. Davidovits, J. 2008. Geopolymer Chemistry
and Applications. Institut Géopolymère, SaintQuentin, France
8. Hambling, D. 2009. "Cool Under Pressure:
Geopolymers Offer Diverse Structural
Benefits." Defense Technology International,
Washington, DC
9. Nagrale, S.D., Dr. Hemant Hajare and Pankaj
R. Modak(2012), Utilization Of Rice Husk
Ash, International Journal of Engineering
Research and Applications (IJERA),Vol. 2,
pp.001-005.
REFERENCES
1. Hansbo, S. (1979), Consolidation of clay by
band shaped prefabricated drains Ground
Eng'g., Vol. 12, No. 5.
2. Indraratna, B. and Redana, I W. (2000),
Behaviour of Vertical Drains in Soft Clay with
Smear and Well Resistance, Canadian
Geotechnical Journal, Vol 37.
3. Schaefer, V.R., (1997), Ground Improvement,
Ground Reinforcement, Ground Treatment
Developments
1987-1997,
Geotechnical
special publication No.69, ASCE, Logan, UT.
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