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Proceedings of Indian Geotechnical Conference

December 22-24, 2013, Roorkee

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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

R.Dayakar Babu, K.Ramu, S.Durga Prasad & K. Ashok Kumar.

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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

Influence of geopolymer on the strength characteristics of sand mixed soft marine clay

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interest in geopolymer applications in transportation infrastructure. Although

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 infrastruc-

ture, although the technology is rapidly advancing

in Europe and Australia. One North American

geopolymer application is a blended portland-

geopolymer cement known as Pyrament® (pat-

ented 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

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 Value

Grain size analysis

Sand 9%

Silt 27%

Clay 64%

Atterberg’s limits

Liquid Limit 78%

Plastic Limit 32%

Plasticity Index 46%

Compaction parameters

OMC 29%

MDD 1.5 gm/cc

Sand

The locally available sand was collected form

Godavari River and conducted proctor compaction


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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.

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.

Trial No Soft Clay Sand Geopolymer

1 100% 0% 0%

2 100% 0% 5%

3 100% 0% 10%

4 100% 0% 15%

5 75% 25% 0%

6 75% 25% 5%

7 75% 25% 10%

8 75% 25% 15%

9 50% 50% 0%

10 50% 50% 5%

11 50% 50% 10%

12 50% 50% 15%

13 25% 75% 0%

14 25% 75% 5%

15 25% 75% 10%

16 25% 75% 15%

17 0% 100% 0%

18 0% 100% 5%

19 0% 100% 10%

20 0% 100% 15%

Influence of geopolymer on the strength characteristics of sand mixed soft marine clay

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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.

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

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. 3 Variation of Angle of Internal Friction (φ)

for different blends of soft clay and sand w.r.t.

different percentages of geopolymer.


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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.

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.

4. Avalle, D L (2007), Ground vibrations during

impact rolling, 10th Australia New Zealand

Conference on Geomechanics (2007), Carillon

Conference Management for the Australian

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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

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7. Davidovits, J. 2008. Geopolymer Chemistry

and Applications. Institut Géopolymère, Saint-

Quentin, 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

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