CHAPTER 1

INTRODUCTION

1.1 General

Rigid plastic foams were developed by BASF in 1950 which have been

consistently used in building construction (BASF, 1990) and in various geotechnical

applications such as pavements (BASF, 1991; 1993), embankments (BASF, 1995)

since 1960s. However, it has been proposed to consider as a geosynthetics material

under a new product category called “Geofoam? (Horvath, 1991). Other names used

previously in geotechnical literature when referring to such materials include

geoblock, geoboard, geoinclusion and geosolid. In India, the application of such

material in various fields was introduced by BASF (2004).

1.2 EPS geofoam material

Expanded polystyrene (EPS) geofoam is a cellular geosynthetic material used

worldwide due to its large number of applications. Here is a brief outline about EPS

geofoam material.

Since the early 1990?s, geofoam has been generic term for any synthetic

geomaterial created in expansion process using a gas (blowing agent) and resulting in

a texture of numerous closed cells. Therefore, geofoam is not just one material or

product but a very diverse family of many different kinds of materials and products.

Expanded Polystyrene (EPS) geofoam is a cellular plastic material. It is a lightweight

material usually in the form of block. The commonly used parameter for EPS

geofoam is density. The density of EPS geofoam is very less compared to other

conventional fill materials used in the foundation practice.

Materials – Several proven geofoam materials exist. There are additional

materials which have been tried over the years but were found to be technically

unacceptable. Geofoam materials can be divided into three major categories:

1. Polymeric (plastic),

2. Cementitious (typically using Portland cement) and

3. Cellular glass

2

The polymeric category is further subdivided depending on the polymer

chemistry and specific manufacturing process used:

? Rigid cellular polystyrene (RCPS), which can be either expanded polystyrene

(EPS) or extruded polystyrene (XPS)

? Polyethylene (PE)

? Polyethylene-polystyrene (PE-PS) blend and

? Polyurethane (PUR)

Despite the relatively large number and variety of geofoam materials, as a

result of more than 40 years of in-ground experience EPS geofoam has emerged

worldwide as a material of choice in most applications.

Product – Geofoam that can only be manufactured in a factory (which

includes the dominant EPS) are typically moulded or cut into the final block or panel

shape required for the particular application. However, field cutting of a block or

panel to accommodate a particular construction situation can easily be done using a

variety of tools. Geofoams such as PUR or FPCC that are foamed in place simply fill

the shape of the volume that panel is to be filled.

1.3 Advantages

1 Compared to conventional fill materials EPS geofoam is almost 100 times lighter.

2 Any shape of required dimension can be prepared.

3 It is moisture resistant, possesses negligible capillarity.

4 Excellent compatibility with other construction materials such as concrete and

steel.

5 EPS geofoam blocks are easy to assemble, placed and do not require skilled

labour which leads to saving in cost as well as time.

6 It has high resistance against growth of bacteria, fungus and insects.

7 It does not interfere with ground water table.

3

1.4 Applications

1 Slope stability

2 Embankment

3 Retaining wall

4 Bridge abutment

5 Pavements

1.5 Organization of the report

The material contained in this thesis is presented as six chapters. A review of

the previous literature published on fly ash in combination with other material and its

uses in geotechnical application and the research needs in present in Chapter (2).

The various materials and their characteristics used in the proposed work for

the development of EPGM material for sustainable construction are described in

Chapter (3).

The basic consideration in the planning of experimental program and detailed

scheme of proposed investigation are presented in Chapter (4).

Development and characteristics of EPGM material is demonstrated in

Chapter (3).

The data obtained from the experimental investigation is analyzed and

interpreted in Chapter (5).

The dissertation concludes with Chapter (6), which highlights the importance

of the work and enlists the broad conclusions derived from the study conducted. This

is followed by the presentation of topics for future research.

Construction of roadway or railway embankments on soft foundation soil such

as marine clay is always a major issue due to poor load carrying capacity and

excessive settlements. In such conditions, two major remedies are available. One is

ground improvement technique by enhancing the engineering properties of foundation

soil and second is reduction in the overburden pressure of structure on foundation soil

this kind of study can overcome such kind of problems.

Considering first remedial measure as a ground improvement technique,

enhancing the engineering properties of foundation soil and its strengthening may be

very difficult due to certain reasons such as differing in soil strata or soil strata may

not be known accurately. However, second remedial measure is to reduce the

4

overburden pressure on foundation soil by using expanded polystyrene (EPS)

geomaterial having well defined properties and it can noticeably reduce the

overburden pressure on foundation soil due to its very low density.

The application of EPS geofoam in geotechnical engineering structures have

been given by several researchers, especially in the construction of embankments and

pavements (e.g. Frydenlund and Aaboe, 1994; Chang, 1994; Duskov, 1997a; 1997b;

Beinbrench and Hillmann, 1997; Duskov and Scarps, 1997; Perrier, 1997; Zou et al.,

2000; Stark et al., 2004;; Horvath, 2008; Arellano and Stark, 2009; Newman et al.,

2010), centrifuge modeling of EPS geofoam embankments Mandal and Nimbalkar

(2000), slope stability analysis (e.g. Jutkofsky et al., 2000; Mandal and Nimbalkar,

2004; Akay et al., 2013).

From the available literature, it is found that most of the work has been

carried out in the direction of actual application of EPS geofoam in the field and a

very little attention has been given towards experimental investigation especially

towards EPS geomaterial in roadway embankments, filling material behind retaining

walls and bridge abutments, for backfilling of pipeline trenches and for irregular

areas. Therefore, an initiative has been taken to study the small scale model testing of

EPS geomaterial for roadway embankments, filling material behind retaining walls

and bridge abutments, for backfilling of pipeline trenches and for irregular area

fillings.

CHAPTER – 2

LITERATURE REVIEW

2.1 General

This chapter presents the overview of various constraints associated with the

disposal Fly-ash and its uses in civil engineering are hereby identified. Also the fly

ash, its physical properties and general uses in various applications is viewed.

However, this lightweight geomaterial technology has not yet found its place in

geotechnical construction practice in our country. In order to make this technology

more relevant and use to, technically sound and cost effective in the present scenario

in India, an effort is made to develop a new EPS beads based lightweight geomaterial

(LWGM) of desired characteristics for its use in embankments over compressible

soils, for reduction in earth pressures in soil retention structures and as backfilling

material. The paper presents the investigations carried out in this respect and the

outcome thereof.

Keeping in view the above objective, this study represents the information

regarding use and application of fly ash based light weight material, stabilized with

small percentage of cement, their properties and uses in a most concise, compact and

to the point manner. Waste materials utilization is not only the promising solutions for

disposal problem, but also saves construction cost of the project to a limit.

The main objective is to investigate the potential of using light weight

materials in the field of geotechnical engineering. While studying various relevant

literatures, various important facts about Fly ash are realized but various important

information about the light weight material is not realized. There is lack of

information about the use and behavior of fly ash as a backfill material. This study,

therefore, seeks to fill this gap.

The present Chapter reviews the attempts made by several researchers to

understand the behavior of expanded polystyrene (EPS) material as a construction

material to minimize the degradation to a level consistent with sustainable

development is reviewed; its procedures and design technologies adopted are studied.

6

Literature reviewed in the present Chapter reveals many studies on the application of

geomaterial in various Civil engineering projects which are important to contribute

the gain of experience and accuracy in framing the future work.

2.2 Advantages of EPGM material as a sustainable backfill material

Nowadays, EPGM is an atypical backfill material, but has a number of qualities that

makes it stand out from other material. Here are its main attributes.

? It is very good fire resistant.

? Light in weight, easily manageable on site.

? Has comparative high strength.

? Can be used in Construction over the soft soil having low bearing capacity.

? Can be used in low lying areas.

? Can be used to reduce the over burden pressure and to economize structures like

retaining wall and embankments, for reduction in earth pressures in soil retention

structures and as backfilling material.

? It can be used as a substitute of EPS block geofoams.

2.3 Literature Review

Lightweight geomaterials using EPS beads

Tsuchida et al. (2001) carried out a series of unconfined compression tests on

geomaterial prepared with expanded polystyrene beads, dredged bay mud and cement.

The engineering properties of geomaterial developed mainly include modulus of

elasticity, compressive strength, and deformation characteristics were studied. The

experimental investigation showed that the secant modulus of geomaterial increases

150-400 times the shear strength obtained from unconfined compression test (qu/2).

The stress reaches to a well defined point and then to the residual state in the direct

shear test. Direct shear tests were also performed on the geomaterial to gain the

correlation between two parameters such as compressive strength test and shear

strength.

7

Yoonz et al. (2004) studied the mechanical characteristics of the light-weighed

soil (LWS) made up of EPS, water, dredged clay and cement through a series of

triaxial compression tests and unconfined compressive test . The test specimens were

prepared in the ratio of EPS, water and cement to dredged clay by percent weight. The

stress-strain characteristics, along with the different parameters affecting the strength

of the light-weight soil such as initial water content in dredged clay, EPS ratio effect,

cement ratio effect, curing pressure effect were studied. The experimental study

revealed that the compressive strength of the LWS does not depend upon effective

confining pressure. The secant modulus obtained at 50% failure strain is about 20-40

times triaxial compressive strength. The influence of initial water content in the

dredged soil is also important as the axial strain in triaxial test decreases significantly

with decrease in initial water content in dredged soil.

Stark et al. (2004b) has discussed the advantages of lightweight fill materials

for embankment by using EPS. These lightweight fill materials have a density less

than soil which reduces the overburden pressure over poor foundation soil such as

marine clay thereby reduces the excessive settlements. It was also reported and

observed that the magnitude of secondary compression of soft soils can be

considerably reduced by using the lightweight materials.

Liu et al. (2006) conducted compressive strength tests to study the effect of

different mixing ratios of EPS beads, cement and water with respect to soil on the

compressive strength, density, modulus of elasticity of the lightweight fill material.

From the experimental investigation, it was observed that, the density of lightweight

material is highly dependent on percentage of EPS beads added in the mix; however

the effect of percentage of cement and water added is insignificant compared less to

EPS beads. The compressive strength of the lightweight material depends on all the

three mixing ratio and it increases with increase in the percentage of cement whereas

decreases with increase in EPS beads and water. The lightweight material produced

has higher density but high compressive strength compared to EPS geofoam block

and can be used as an optional material when high strength fill materials are required.

Kim et al. (2008) developed a lightweight soil consisting of dredged clayey

soil, cement, and air-foam with waste fishing net as reinforcement for the material. A

series of unconfined compression tests and one dimensional compression tests were

8

conducted to investigate the strength characteristics of unreinforced and reinforced

lightweight soil with fishing net. The lightweight soil specimens were prepared with

different composition of cement, water, air-foam and fishing net contents. The results

showed that the compressive strength increases with increase in cement content but

decreases with increase in water and air-foam content. Inclusion of waste fishing net

increases the compressive strength of lightweight soil due to the friction and the bond

strength at the interface between waste fishing net and soil mixtures; however

increase in the compressive strength was not directly proportional to the percentage of

waste fishing net. The air-foam content affected the bulk unit weight of lightweight

soil.

Zhu Wei et al.(2008)developed a new geo technical material, sand EPS beads

mixture (SEM).Direct shear tests, density test and compression test were performed to

study the density and strength properties of the SEM. The results showed and revealed

that i) water is necessary for preparation of specimen, but has no different effect on

shear strength and dry density of the SEM, ii) dry density of the SEM decreases

linearly with volumetric EPS beads content, but increases with preload pressure, and

iii) the shear strength of the SEM changes little with volumetric EPS beads content

and gravimetric water content but increases with preload pressure.

Wang and Miao (2009) performed laboratory experimental to study the

effectiveness of fill material made from different mixtures of river sand, cement and

expanded polystyrene beads. The proportion of sand and EPS beads was measured by

volume, while the proportions of sand, water and cement were determined by weight.

The compaction test was conducted with different water content proportion to obtain

the optimum water content. The test specimens of cubical shape were prepared using

the density and water content determined already. The unit weight of lightweight fill

material produced was 10 kN/m3. These specimens were tested for unconsolidated

undrained triaxial test, consolidated undrained test, unconfined compression test. The

outcomes showed that the unconfined compressive strength of proposed material

increases with the increase in curing time and cement content. In unconsolidated

undrained triaxial test, it was observed that the cohesion of lightweight material has

strong influence of cement content; whereas angle of internal friction was not affected

much when tested for 7 days and 14 day cured specimen. In consolidated undrained

test, with increase in cement content increases the cohesion value whereas the angle

9

of internal friction of soil was found to almost the same compared to UU test. The

performance of lightweight fill material was also studied by construction of

embankment over soft soil by using 2 dimensional finite element analysis package

PLAXIS 2D. The results obtained from FEA were then compared with similar soil

embankment stabilized with lime. The results indicated and revealed that there is

considerable reduction in the settlement of soft soil with better strength of

embankment with lightweight material when compared with the lime stabilized soil

embankments.

Deng and Xiao (2010) conducted and performed consolidated drained triaxial

tests on EPS sand mixtures to observe the stress-strain characteristic under different

confining pressures. The EPS-sand mixtures were produced by adding 0.5, 1.5 and

2.5% of EPS beads by weight of sand which was found to be 26 to 63% lighter than

the conventional fill materials. The triaxial specimens were loaded under confining

pressures of 100, 200, 300 and 400 kPa. The results of the investigation showed and

revealed that the EPS content and confining pressures were found to be major

influencing parameters to the stress-strain and volumetric strain behavior of the

mixtures. Increase in EPS content increases volumetric strain and decreases the shear

strength. Increase in confining pressures enhances the strength of the mixture. EPS

content dependent strain increment equations were also derived by compromising

Cam-clay and modified Cam-clay, and used to model the stress-strain characteristics

of EPS-sand mixtures. The established equations were verified being able to depict

the stress-strain observations of EPS-sand specimens, at least for the ranges of EPS

contents and confinements.

Onishi et al. (2010) carried out series of triaxial compression tests on cement

stabilized sand with EPS beads. The change in strength and deformation properties

with increase in EPS beads content is studied and observed. The findings reported that

the unit weight of the geomaterial produced can be reduced to a greater extent by

addition of EPS beads but on the other hand mixing of such material can degrade the

strength and deformation properties of the geomaterial. However, this degradation can

be effectively controlled by addition of appropriate amount of cement. Based on the

outcomes from the study, the practical implications of designs of these types of

lightweight geomaterials are also discussed in terms of unit weight, strength and

deformation characteristics.

10

Gao et al. (2011a) discussed the geotechnical properties of lightweight

geomaterial called EPS composite soil (EPSCS) made up of clay, cement, water and

EPS. The properties such as unit weight, compressive strength and modulus,

deformation behavior, permeability, dynamic property using creep behavior, cyclic

triaxial test and water absorbability. The advantages of the lightweight geomaterial in

the geotechnical applications are discussed with some case histories. Based on this

study, some future scope of research is also suggested and projected.

Gao et al. (2011b) carried out a series of cyclic triaxial tests to understand the

strength and deformation characteristics of lightweight sand EPS soil (LSES). A

united framework was suggested for LSES for setting up deformation and strength

characteristics by failure cyclic number that corresponds to complete degradation of

LSES structure. Cylindrical shaped test specimens with diameter 61.8 mm and height

140 mm were prepared using different mix ratios. The cyclic stress-strain relationship

along with Modulus Reduction Curves for LSES was studied. The experimental

investigation showed that LSES possesses good resilient- elasticity recovery ability

due to presence of EPS beads which play an important role in energy consumption,

affected by which, the cyclic stress–strain curves of LSES under low confining

pressures show remarkably linear type. The behavior of LSES under cyclic loading

was found to be clearly different from those of sand or cemented sand or EPS. The

LSES specimens exhibit brittle failure.

Gao et al. (2012) performed 2D finite element simulation of the embankment

constructed with lightweight geomaterial (EPSCS already mentioned in Gao, 2011a)

having unit weight 11 kN/m3 over soft clay to determine and study the settlement, soil

pressure and pore water pressure and to improve the safety of the ground. The

comparison was made between EPSCS and embankment with conventional fill

material having unit weight of 18 kN/m3. Compared with the conventional

embankment, EPSCS embankment can effectively reduce the settlement problems,

soil pressure and excess pore water pressure and so as to improve and safe guard the

safety of the ground.

Miao et al. (2013) proposed a new lightweight fill material consisting of EPS

beads, cement and the hydraulic sand from the Yangtze River, for its application in

settlement problems associated with bridge approach embankments over soft soil. The

11

experimental investigation and study was carried out to understand the mechanical

properties of lightweight material such as standard Proctor tests, unconfined

compression tests, unconsolidated-undrained tests, California Bearing Ratio (CBR)

tests, and consolidated-undrained tests. The test results showed that proposed

lightweight fill material possess consentient properties which suit as a backfill

material in highway embankment projects. A field study was also performed to verify

the performance of the embankment backfilled with this lightweight material, which

resulted in a smaller settlement than the embankment backfilled with lime-stabilized

soil.

Qi et al. (2013) conducted permeability tests on geomaterial prepared with

EPS beads, sand and cement. The effect of different mixing ratios, curing age and

applied consolidation pressure on permeability of the geomaterial produced was

studied through laboratory experimental tests using consolidation parameter. The test

results indicated that the permeability of EPS beads-mixed lightweight soil decreases

with the increasing of curing age and cement ratio, and decreasing of EPS beads ratio

and particle size. The coefficient of permeability of EPS beads-mixed lightweight soil

decreases with the increase of consolidation pressure and the decreasing trend is slow

down under large consolidation pressure. The extent of reduction of permeability

coefficient with the increase of consolidation pressure is comparatively larger under

large EPS beads ratio or small cement ratio.

Padade and Mandal (2014) conducted a study of Expanded Polystyrene-Based

Geomaterial with Fly Ash. This paper reports the engineering behavior of proposed

expanded polystyrene-based geomaterial (EPGM) with ?y ash through a laboratory

experimental study. The proposed geomaterial is prepared by blending ?y ash with

expanded polystyrene (EPS) beads and a binder such as cement. The effects of

different compositions and different mix ratios between EPS beads and ?y ash (0.5–

2.5%), cement and ?y ash (10–20%), and water and ?y ash (50 and 60%) on density,

compressive strength, and initial tangent modulus of the geomaterial formed were

studied for 7 days and 28 days duration. The authors observe that the density of

EPGM can be effectively controlled by the quantity of EPS beads added in making

the material. With the inclusion of merely 0.5–2.5% of EPS beads to ?y ash (by

weight), the density of the geomaterial formed can be reduced from1,320 to 725

kg/m3. The compressive strength of EPGM increases considerably if cement-to-?y

12

ash ratios of 10, 15, and 20% are used. Compared with EPS block geofoam, EPS

beads mixed geomaterial has higher density but higher compressive strength and

higher stiffness. Thus the geomaterial developed in the current study can be used as a

substitute for EPS geofoam block when strong ?ll materials with high strengths are

required.

Ram Rathan Lal and Badwaik (2015) conducted experimental study on bottom

ash and expanded polystyrene beads–based Geomaterial. The increasing production of

bottom ash and its disposal in an eco-friendly manner is a matter of concern. This

paper concisely describes the suitability of bottom ash to be used in civil engineering

applications as a way to minimize the amount of its disposal in the environment and

in the direction of sustainable development. The proposed geomaterial was prepared

by blending bottom ash with expanded polystyrene (EPS) beads and a binder such as

cement. The experiments were conducted by adding EPS beads with different mix

proportions. The mix ratio percentages 0.3, 0.6, 0.9, 1.2, and 1.5 were used in this

study. The cement to bottom ash (C/BA) ratios of 10 and 20% were used in the study.

All the ratios used in the study are with respect to weight of bottom ash. The

compressive strength of geomaterial was evaluated for curing periods of 7, 14, and 28

days. The effects of various mix ratios, cement content, and curing periods on the

density, compressive strength, and initial tangent modulus was studied and the results

were incorporated. Test result indicated that the density of geomaterial reduced from

650 to 360 kg/m3 with addition of EPS beads from 0.3 to 1.5%. For a particular

curing period, compressive strength reduced marginally following the inclusion of

EPS beads in geomaterial. For each mix ratio, compressive strength increased with

increasing curing periods. The initial tangent modulus of the geomaterial decreased

with increasing mix ratio values. The prepared geomaterial was light in weight

comparatively and it can be used as a substitute to conventional fill materials.

Marjive and Ram Rathan Lal(2016)carried out an experimental study on stone

dust and EPS beads based material, a series of compressive strength were performed

on newly developed construction material (NDCM) prepared by using stone dust,

expanded polystyrene (EPS) beads and binder material such as cement. Two different

densities of EPS beads 22 kg/m3 and 16 kg/m3 were used in this study. The mix ratio

percentages used in the study are 0.25, 0.75, and 1.25. The compressive strength of

material was determined for curing periods of 7, 14, and 28 days. For a particular mix

13

ratio value, compressive strength of material increased with increasing curing period

and for a particular curing period value it decreased with increasing mix ratios. The

density of NDCM was found to be decreased with increasing mix ratios for both the

densities EPS beads. For a particular mix ratio, NDCM prepared using EPS beads of

density 16 kg/m3 shows lower density than that of prepared using density 22 kg/m3.

For a particular mix ratio and for each curing days, NDCM prepared using EPS beads

of density 22 kg/m3 shows higher compressive strength than EPS beads of density 16

kg/m3.

Ashna et al. (2017) carried out an experimental study on stress-strain behavior

of EPS beads-sand mixture. In this study, Expanded Polystyrene beads of two sizes,

namely 1 mm and 2 mm were mixed with sand at proportions 0.25%, 0.5% and 0.75%

by weight to obtain a new geo-material. A Tri-axial compression test was done at

three different confining pressures. The results showed that by increasing the EPS

content by weight, maximum deviator stress and angle of internal friction decreased.

However, bead in the mix contributed to the lightweight aspect which can be used in

several geotechnical applications. The stress strain behavior of the mix was found to

be dependent on size of bead, bead content and confining pressures. The study

concluded with, dry unit weight decreases with the addition of EPS beads into sand

which shows that it has the potential characteristic of a lightweight fill, Angle of

internal friction decreased with increase in bead content, Deviatoric stress decreased

with increase in % by weight of beads for both bead sizes, Smaller sized beads

showed greater strength compared to larger sized beads was observed.

From available permanent literature, lightweight geomaterials are prepared by

using EPS beads, soil and cement as binder material (Tsuchida et al., 2001; Yoonz et

al., 2004; Stark et al., 2004b; Liu et al., 2006; Kim et al, 2008; Wang and Miao, 2009;

Deng and Xiao, 2010; Onishi et al., 2010; Gao et al., 2011a; 2011b; 2012; Miao et al.,

2013 ; Qi et al., 2013), a few study has been done by using EPS beads, fly ash and

cement as binder material (Padade and Mandal 2014, Ram Rathan Lal and Badwaik

2015; Marjive and Ram Rathan Lal 2016; Ashna et al 2017). However, it is observed

that some of the aspects of mix ratios are not discussed adequately in the study.

As studied and reported by Liu et al. (2006), the usage of EPS geofoam blocks

in infrastructure projects suffer from some disadvantages viz. (i) EPS geofoam blocks

14

are usually of regular shapes, therefore it is not possible to use them to fill in irregular

volumes; (ii) shapes EPS geofoam blocks cannot be fabricated on site, hence its

transportation is necessary on site and (iii) So as to suit site conditions the basic

properties of EPS geofoam blocks cannot be modified.

Several researchers have done experimental and numerical investigations on

lightweight fill material prepared by using EPS beads, soil and cement (e.g. Tsuchida

et al. 2001, Yoonz et al. 2004; Liu et al. 2006; Kim et al. 2008; Wang and Miao 2009;

Deng and Xiao 2010; Onishi et al. 2010; Gao et al. 2011a, 2011b, 2012; Miao et al.,

2013 and Qi et al. 2013). A few research by Padade & Mandal 2014; Ram Rathan Lal

& Badwaik 2015; Ram Rathan Lal et al. 2016; Ashna et al. 2017 in the light of using

fly ash as EPGM material has been done. Shin et al. (2011) proposed application of

light soil particles (LSP) made of expanded polystyrene (EPS) material in mortar.

It is well studied from the available literature that numerous studies have been

carried out to understand the behavior of lightweight geomaterial (EPGM) prepared

by using EPS beads, soil and cement as binder material. However, much attention is

not paid to develop geomaterials by using fly ash instead of soil or any other material

in combination with EPS beads and cement.

As per the problems mentioned and detailed by Das and Yudbhir (2005) and

Gandhi et al. (1999), Padade & Mandal 2014 the present research work was carried

out by using fly ash and EPS beads in the light of long term strength gained by the

specimens in comparison with specimens prepared without beads.

Fly ash is the finely divided residue that results from the combustion of

pulverized coal and is transported from the combustion chamber by exhaust gases.

Over 61 million metric tons of fly ash was produced in 2001.The total generation of

fly ash in 2010-11 was 131.09 million-tonnes. The data of fly ash generation and

utilization for year 2015-16 received from 71 Power Utilities in India was 176.7441

Million- tonne which is 2.6 times more as compared to 2001 report .Therefore with an

exponential increase in population of India there has been increasing in power

demand and supply. This directly led to increase in production of fly ash. Leading to

direct impact on global environment. In India, thermal power plants produce a huge

quantity of fly ash. Therefore, an attempt has been made in the direction of using fly

ash instead of soil for the preparation of geomaterial along with EPS beads and

cement.

15

The present study mainly focuses on mechanical behavior of EPS based

geomaterial using fly ash and cement as binding material. Compared with other

similar geomaterials like EPS geofoam blocks, and cement-soil-EPS lightweight fills

the proposed EPGM has some advantages that includes cement saving, irregular shape

filling and indirectly proper utilization of fly ash in geotechnical engineering

application which reduces the environmental pollution related problems to disposal of

fly ash and finally better to overcome the thermal insulation problems. In comparison

with the EPS geofoam block, the lightweight fill that includes EPS beads may be

controlled in terms of both density, shear strength, compressive strength .

2.4 Main Aims and Objectives of the Proposed Work

The primary aim of this study was to investigate the feasibility of using a

significant proportion of fly-ash for beneficial purpose in civil engineering

applications that is sustainable and environmentally friendly. To study strength

characteristics of fly ash and EPS beads in combination with cement and water. This

study reports the results of an experimental investigation into the engineering

properties, such as compressive strength depending on the proportion of beads to fly

ash, cement to fly ash, water to fly ash ratio.

The objective is also to promote safe uses of fly ash material along with EPS

beads in civil engineering projects. The detailed laboratory investigations were

planned and carried out for the determination of the best product and the best mix

design. Thus, the main objective of the study undertaken in this dissertation work may

be summarized as under:

i The primary objective of the present study deals with determination of

physical properties of locally available fly ash and its suitability as a

construction material.

ii To evaluate compressive strength of specimen prepared from different

composition of EPS beads, cement and water along with fly ash and study its

long term strength and stiffness.

iii Preparation of lightweight material using the proportions mentioned by

Padade & Mandal (2014)

iv Density measurement for light weight material.

v Effect of mix ratios on density, compressive strength and stiffness.

16

vi Stress-Strain behavior of the material.

The optimal mixture of locally available fly ash stabilized with cement and

EPS beads was selected among experiments under consideration to produce the

alternative EPGM material mix.

2.5 Scope of Present Work

Considering above stated aims and objectives, the scope of present work is defined as

follows,

A new expanded polystyrene (EPS) based geomaterial has been proposed with

different mix ratios between the four components (EPS beads, fly ash, cement and

water). The mix ratios were based on fly ash as basic material with respect to which

mass of EPS beads, cement and water were taken. The geomaterial has been prepared

with thirty six different combinations and test results of 144 samples of EPS beads

based geomaterial are discussed with respect to the long term effect of these mix

ratios on density, stress-strain nature, variation in compressive strength, effect of

curing period on strength development and initial tangent modulus is determined and

presented in the study.

a. The lightweight geomaterial (LWGM) evolved from the study by using fly ash and

expanded polystyrene beads has high potential for its use in several geotechnical

constructions in infrastructure development works in India.

b. The composite material of required lightness and strength can be formed by

adjusting EPS beads (B) content from 0.5% to 2.5% of weight of fly ash (FA).

However, for appropriate strength development 10%, 15%and 20% cement (by

weight) is needed.

d. As compared to traditional coarse grained moorum type earth commonly used in

embankment construction and backfilling, the suggested LWGM is 50% light and

16.5 times strong.

e. The LWGM developed from the study can be used in the form of blocks of any size

pre-casted and cured at casting yard near site or as wet mix to be placed in bulk for

the desired construction job.

17

f. Embankments with very steep slopes can be formed by using LWGM. This results

in substantial saving of land area occupied by embankment. Besides, the volume of

embankment material is significantly reduced.

CHAPTER 3

MATERIALS

3.1 Fly Ash

Flyash, is known as one of the residues generated by coal combustion, and is

composed of the fine particles that are driven out of the boiler with the flue gases. The

fly ash is continuously produced in unimaginably huge quantity in our country from

several thermal power plants. In absence of its timely and effective disposal it creates

many environmental hazards. This fly ash forms the main constituent of the proposed

geomaterial. Fly ash is an industrial waste product from coal based power station.

The fly ash is slightly alkaline in reaction. Fly ash is a good material for a

wide range of applications viz. by geopolymerisation, by preprocessing, by heat

treatment process can be utilized for manufacturing of cement, substitute of cement in

concrete, manufacture of bricks, blocks, ceramic tiles, paving blocks, self glazed tiles,

immobilization, mechanical activation, refractory bricks, synthetic granite etc.

Classification of Fly ashes classified by precise particle size requirements, thus

assuring a uniform, quality product. In the present study fly ash is collected in wet

state from Koradi thermal power plant, Koradi, Nagpur, India having specific gravity

2.18 Class F fly ash is available in the largest quantities. Class F is generally low in

lime, usually under 15 percent, and contains a greater combination of silica, alumina

and iron (greater than 70 percent) than Class C fly ash. Class C fly ash normally

comes from coals which may produce an ash with higher lime content generally more

than 15 percent often as high as 30percent. Elevated CaO may give Class C unique

self-hardening characteristics.

Fly ash used for the present laboratory study is taken from Koradi power plant,

Nagpur which is stored in gunny plastic bags and it is classified as class F. Flyash

having following components are summarized below,

The percentage of basic chemical compounds present in fly ash were SiO2

(61.15%), calcium oxide, CaO (3.31%),Magnesium oxide, MgO(0.64%),total Sulphur

as Sulphur trioxide ,SO3(0.127%),Silicon dioxide (SiO2) +aluminium oxide(Al2O3)+

iron oxide(Fe2O3) (94.95%),Total loss on ignition was (0.34%). Depending on

percentage of chemical compounds present in fly ash, as per ASTM C618-08, it is

classified as Class F. The specific gravity of fly ash is 2.18. Fineness by sieving is

19

9.30%, compressive strength 28 days is 34.50N/mm2, consistency as 27.5%,

soundness by Autoclave method as 0.039% respectively.

3.2 Expanded polystyrene beads

Expanded Polystyrene (EPS) is a super lightweight synthetic cellular material

that was invented in 1950. This rigid plastic foam type material is being used in

geotechnical constructions since 1960’s when a product category ‘Geofoam ‘was

discovered. EPS is generally used as packaging material for sensitive appliances and

electronic items during transportation. EPS is a polymeric form of its monomer,

Styrene. It is white in colour, and is manufactured from a mixture of 5-10% gaseous

blowing agent, most commonly pentane or carbon dioxide and 90-95% polystyrene by

weight. The solid plastic is expanded into foam by the use of heat; usually steam. EPS

can be used in the form of blocks (also called EPS geo-foam) and beads. Expanded

polystyrene beads used are spherical and round in shape with diameters ranging

between 2 to 3 mm. These highly compressible EPS beads have a density 20 kg/m3.

Compared to EPS shreds and strips, EPS beads make the composite material with the

lowest unit weight.

An expanded polystyrene bead was used as a mixing component. These closed

cell particulates are often called as polystyrene pre-puffs in the manufacturing sector.

The lightness of the material is accomplished by adding EPS beads in fly ash.

Expanded polystyrene beads were spherical and round in shape with diameters

ranging between 2 to 4 mm and having durable property. It was aimed to develop a

composite material containing larger percentage of EPS beads and lesser quantity of

cement. The trial mixing and testing revealed that the beads content should be 0.5% to

2.5% of the weight of fly ash. EPS beads having the chemical formula (C8H8) n,

density in the range of 0.96 -1.04 gm/cm3, having melting point approximately 240oC

(464oF) and decomposes at lower temperature, thermal conductivity 0.033 W/ (m-k),

Refractive index (nD) 1.6; dielectric constant 2.6(1KHz-1GHz), was obtained from a

regional supplier of EPS material for engineering, packaging, manufacturing

industries Thermo Pack Industries, Kalamna market road, Nagpur, India.

3.3 Cement

An Ordinary Portland cement of 43 grade (IS 8112: 1989) was used as a

binding material. Cement is a binder, a substance used for construction that sets,

hardens and adheres to other materials, binding them together. Cement is seldom used

20

on its own, but rather to bind sand and gravel together. The density of ordinary

Portland cement was 3.15 g/cm³(3150 kg/m3). This type of cement should confirm

according to IS: 8112-1989.

3.4 Water

Potable water is used to mix these materials. Potable is water safe enough to

be consumed by humans or used with low risk of immediate or long term harm. In

most India, the water supplied to households, commerce and industry meets drinking

water standards, even though only a very small proportion is actually consumed or

used in food preparation. Typical uses (for other than potable purposes) include toilet

flushing, washing, and landscape irrigation.

Figure 3.1 Photographic view of EPS beads

CHAPTER 4

EXPERIMENTAL PROGRAM

The experimental program was planned with an objective to understand and

investigate the suitability of fly ash. The following chapter discusses the laboratory

equipment, method and techniques utilized throughout the testing program.

4.1 Mix proportion

The work plan comprise of mix proportions and preparation of specimens with

several different combination of Fly ash, Cement at suitable W.C. (%). In the

experimental study three different mix ratios were used to prepare the EPGM. The

mix proportion is defined as the proportion of two materials by weight. These ratios

are as follows –EPS beads to fly ash (B/FA), cement to fly ash ratio (C/FA), and

water to fly ash (W/FA). A pilot project work was also conducted before deciding the

range of limits of different mix ratios and specimen of size 100 X 100 X 100 mm was

taken into consideration. During the sample preparation it was observed that beyond

2.5% proportion of (B/FA) ratio the sample segregates, due to volumetric increase of

beads as compared to fly ash .The cement to fly ash ratio (C/FA) was also fixed

between 10% to 20% because C/FA ratio below 10% was insignificant as the

components were found to be segregated after curing of one day. And the last

component of water to fly ash ratio (W/FA) ratio cannot be formed into homogeneous

slurry below water to fly ash of 40%. Table gives the study for preparation of the

EPGM.

Table 4.1 Mix ratios used to prepare EPGM

Mix ratios

EPS beads to fly ash

(B/FA)%

Cement to fly ash

(C/FA)% Water to fly ash (W/FA)%

0.5, 1.0, 1.5, 2.0, 2.5 10 40

0.5, 1.0, 1.5, 2.0, 2.5 15 40

0.5, 1.0, 1.5, 2.0, 2.5 20 40

0.5, 1.0, 1.5, 2.0, 2.5 10 50

0.5, 1.0, 1.5, 2.0, 2.5 15 50

0.5, 1.0, 1.5, 2.0, 2.5 20 50

NOTE: B/FA = EPS beads to fly ash ratio and C/FA= Cement to fly ash ratio

22

4.2 Experimental Program

Experimental program consists of determination of

? Preparation of lightweight material using the proportions mentioned by Padade ;

Mandal (2014)

? Density measurement for light weight material.

? Compressive strength test for long term of 7/14/28/56 days on cubical specimen.

? Effect of mix ratio on density, compressive strength and stiffness.

? Stress-strain behavior of the material.

4.3 Preparation of test specimen

The EPS beads mixed geomaterial was prepared as follows. The dried fly ash

was weighed and placed into a container. The cement was also added according to

C/FA ratio and dry mixing was carried out first. For compound mix, potable water

was added slowly according to W/FA ratio specified and the fly ash–cement-water

mixture was mixed into homogeneous slurry as shown in Figure 4.1(a). The EPS

beads were then slowly added into slurry and mixing continued until the beads were

evenly distributed well within the slurry. With some more time of mixing, fresh EPS

beads mixed geomaterial was produced in a slurry form as shown in Figure 4.1(b).

After a thorough mixing the slurry formed was cast into specimens for compressive

strength tests. These compressive strength test specimens were prepared in a cube

shape moulds having dimension 100 mm × 100 mm × 100 mm as shown in Figure

4.2. After setting time, all specimens were removed from the moulds and placed in the

water tank for curing until the date of testing as shown in Figure 4.3. The EPGM

specimens after curing are shown in Figure 4.4. The curing periods used in

experimental program were 7 days, 14 days, 28 days and 56 days. 30 tests were

conducted on EPGM samples for each curing period. Therefore, the results of 120

tests are reported in the study along with test results of 24 tests obtained from mixing

of fly ash along with cement and water without beads for a comparative study.

23

(a) (b)

Fig. 4.1 Preparation of EPGM (a) dry cement and fly ash mix and

(b) slurry after mixing of EPS beads and water

Fig. 4.2 EPGM specimen casting in moulds

Fig. 4.3 EPGM specimens in curing tank

24

Fig. 4.4 EPGM specimens after curing

4.4 Test procedure

After curing, the specimens were air dried and dimensions of each specimen

were measured using a vernier calliper for volume determination (Figure 4.5 a ). The

mass of each specimen was measured using an electronic balance having accuracy of

0.01 g. These measurements were used to calculate the density of specimen by

dividing mass with volume.

Compression test was performed on EPGM specimens to measure

compressive strength and stiffness. Compression tests were conducted in load frame

machine at a deformation rate of 1.2 mm/min as shown in Figure 4.5(b) having a

capacity of 5 tonnes. The maximum load at failure of specimen with corresponding

deformation was noted as a compressive strength.

25

(a) (b)

(Fig. 4.5 a) Specimen measured with vernier calliper

4.5 b) Compressive strength tests on EPGM test specimen on load frame

machine.

Apparatus:

Load frame Machine, cube specimen.

Procedure:

• After preparing a mix, the cubical test specimens of dimensions 100x100x100 mm is

prepared for compressive strength.

• The Compressive Strength test was performed as shown in the figure.

• The specimen is placed between steel plates under loading frame.

• Load is applied axially at uniform rate till failure.

• Maximum load at failure divided by average area of bed face gives compressive

strength.

26

Calculation

Compressive Strength (kN/m2) =;#3627408396;;#55349;;#56346;;#55349;;#56369;.;#3627408421;;#3627408424;;#55349;;#56346;;#3627408413; ;#55349;;#56346;;#3627408429; ;#3627408415;;#55349;;#56346;;#3627408418;;#3627408421;;#3627408430;;#3627408427;;#3627408414; ;#3627408418;;#3627408423; ;#3627408420;;#3627408397;

;#55349;;#56320;;#3627408431;;#3627408414;;#3627408427;;#55349;;#56346;;#3627408416;;#3627408414; ;#55349;;#56320;;#3627408427;;#3627408414;;#55349;;#56346; ;#3627408418;;#3627408423; ;#3627408422;;#3627409360;

(a) (b)

Fig. 4.6a) Cube Compressive strength test set up

b) Cube specimen after failure

4.4.2 Determination of Density

One of the important parameter for EPGM is its density. The specimens were weighed

by using electronic weighing balance. The density of the material block was

calculated by dividing weight with volume of the specimen.

Apparatus

? Electronic weighing balance.

Calculation

Density =;#3627408406;;#3627408414;;#3627408418;;#3627408416;;#3627408417;;#3627408429; ;#3627408424;;#3627408415; ;#3627408428;;#3627408425;;#3627408414;;#3627408412;;#3627408418;;#3627408422;;#3627408414;;#3627408423;;#3627408429; ;#3627408418;;#3627408423; ;#3627408420;;#3627408397;

;#3627408405;;#3627408424;;#3627408421;;#3627408430;;#3627408422;;#3627408414; ;#3627408424;;#3627408415; ;#3627408428;;#3627408425;;#3627408414;;#3627408412;;#3627408418;;#3627408422;;#3627408414;;#3627408423; ;#3627408418;;#3627408423; ;#3627408422;;#3627409361;

27

4.4.3 Stiffness modulus

4.4.3.1 Initial Tangent Modulus

The initial tangent modulus, Ei , is often used to characterize the stiffness of the

geomaterial. It is determined as the slope of the tangent line to the origin of the stress–

strain curve. Using the compressive testing results, the initial tangent modulus of the

alternative geomaterial were calculated and plotted against the corresponding

compressive strengths.

CHAPTER 5

RESULTS AND DISCUSSIONS

5.1 General

The properties of lightweight geomaterial such as density, compressive

strength and initial tangent modulus are studied and discussed in this chapter in detail

corresponding to different mix ratios used for its preparation.

5.2 Effect of mix ratios on density of lightweight geomaterial

Figures 5.1 and 5.2 represent the variation of density with respect to B/FA

ratio. It can be clearly noted that the density of lightweight geomaterial decreases with

increase in B/FA ratio. Lightweight geomaterial with B/FA ratios 0 to 2.5% have

density in the range of 1665 to 772 kg/m3. This is due to the weight of EPS beads

which is very less compared to fly ash. Replacement of nearly 0.5% beads increases

its volume significantly which results in dreased density of geomaterial. Increase in

B/FA ratio from 0.5 to 2.5% reduces the desnity of geolmaterial in the range of 19 to

51%. However, increse in C/FA ratio does not show any effect on density of

lightweight geomaterial. Increase in C/FA ratio from 10 to 20% resulted in density

variation within 0.5 to 1%. The change in density of lightweight geomaterial is

noticable for B/FA ratio however, it is insignificant for C/FA ratio.

The density of lightweight geomaterial decreases with increase in W/FA ratio

but the change is marginal. Increase in W/FA ratio from 40 to 50% decreases the

density of lightweight gematerial within the range of 1 to 3%.

From above discussions, it is very clear that B/FA ratio is a governing factor

density of geomaterial whereas the other factors (C/FA) and (W/FA) do not have any

effect on density.

29

(a)

(b) 0

500

1000

1500

2000

0.00.51.01.52.02.53.0

Density,

?(kg/m

3)

B/FA(%)

C/FA=10%C/FA=15%C/FA=20%

7 Days

W/FA = 40% 0

500

1000

1500

2000

0.00.51.01.52.02.53.0

Density,

?(kg/m

3)

B/FA (%)

C/FA=10%C/FA=15%C/FA=20%

14 Days

W/FA = 40%

30

(c)

(d)

Figure 5.1 Effect of B/FA ratio on density of geomaterial at C/FA ratio 40% for

W/FA ratios (a) 7 days, (b) 14 days, (c) 28 days and (d) 56 days 0

500

1000

1500

2000

0.00.51.01.52.02.53.0

Density,

?(kg/m

3)

B/FA (%)

C/FA=10%C/FA=15%C/FA=20%

28 Days

W/FA = 40% 0

500

1000

1500

2000

0.00.51.01.52.02.53.0

Density,

?(kg/m

3)

B/FA (%)

C/FA=10%C/FA=15%C/FA=20%

56 Days

W/FA = 40%

31

(a)

(b) 0

500

1000

1500

2000

0.00.51.01.52.02.53.0

Density,

?(kg/m

3)

B/FA (%)

C/FA=10%C/FA=15%C/FA=20%

7 Days

W/FA = 50% 0

500

1000

1500

2000

0.00.51.01.52.02.53.0

Density,

?(kg/m

3)

B/FA(%)

C/FA=10%C/FA=15%C/FA=20%

14 Days

W/FA = 50%

32

(c)

(d)

Figure 5.2 Effect of B/FA ratio on density of geomaterial at C/FA ratio 50% for

W/FA ratios (a) 7 days, (b) 14 days, (c) 28 days and (d) 56 days

0

500

1000

1500

2000

0.00.51.01.52.02.53.0

Density,

?(kg/m

3)

B/FA(%)

C/FA=10%C/FA=15%C/FA=20%

28 Days

W/FA = 50% 0

500

1000

1500

2000

0.00.51.01.52.02.53.0

Density,

?(kg/m

3)

B/FA(%)

C/FA=10%C/FA=15%C/FA=20%

56 Days

W/FA = 50%

33

Considering the above graphical representation given in Figures 5.1 and 5.2

which shows nearly equal values for the density with respect to C/FA ratio as

discussed earlier, the average density was calculated considering the curing period

and plotted against C/FA ratio as shown in Figures 5.3 (a) and (b). For the specimen

cured for 7, 14, 28 and 56 days, the change in density of geomaterial is found to be

insignificant.

(a)

(b)

Figure 5.3 Effect of mix ratio on density of geomaterial with C/FA ratio

for (a) 40% and (b) 50%

0

500

1000

1500

2000

510152025

Average Density,

?a(kg/m

3)

C/FA (%)

B/FA = 0%B/FA = 0.5%B/FA = 1.0%

B/FA = 1.5%B/FA = 2.0%B/FA = 2.5%

W/FA= 40% 0

500

1000

1500

2000

510152025

Average Density,

?a(kg/m

3)

C/FA (%)

B/FA = 0%B/FA = 0.5%B/FA = 1.0%

B/FA = 1.5%B/FA = 2.0%B/FA = 2.5%

W/FA= 50%

34

5.3 Effect of mix ratios on compressive strength

Figures 5.4 and 5.5 represent the effect of B/FA ratio on compressive strength

of geomaterial. It is important to note that the representation of relationship between

compressive strength and mix ratios are given on same scale for all the cases. This is

done to identify the nature of the geomaterial with respect to beads (B/FA), cement

(C/FA), water (W/FA) and curing period.

The compressive strength decreases with increase in B/FA ratio from 0.5 to

2.5%. Within this range the change in compressive strength was found to be 25 to

68%. The decrease in compressive strength was observed due to increase in the

proportion of highly compressible beads in the mix. It is important to note that 0.5%

increase in beads by weight substantially increases its volume resulted in reduced

compressive strength. However, the strength increases with increase in C/FA ratio

from 10 to 20% for a particular B/FA ratio having same W/FA ratio.

Increase in W/FA ratio affects the compressive strength of geomaterial which

decreases with increase in W/FA ratio from 40 to 50%. Within this range of increase,

the decrease in compressive strength is found to be in the range of 7 to 16%.

Therefore, it can be referred that the mixing ratios required high precision with

respect to W/FA ratio.

It is interesting to observe that specimen without EPS beads have compressive

strength less than specimen with 0.5% beads and equal or some times less than 1.0 to

1.5% beads for most of the cases. This has been clearly observed in stress-strain

curves and discussed in detail therein. The nature of relationship between compressive

strength and B/FA is found to be non-linear for all the cases.

35

(a) (b)

(c) (d)

Figure 5.4 Effect of mix ratio on compressive strength of geomaterial with C/FA ratio

at W/FA ratio 40% for (a) 7 days, (b) 14 days, (c) 28 days and (d) 56 days

0

2000

4000

6000

8000

10000

00.511.522.53

Compressive Strength,

?(kPa)

B/FA (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

7 Days

W/FA=40% 0

2000

4000

6000

8000

10000

00.511.522.53

Compressive Strength,

? (

kPa)

B/FA (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

14 Days

W/FA=40% 0

2000

4000

6000

8000

10000

00.511.522.53

Compressive Strength,

? (

kPa)

B/FA (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

28 Days

W/FA=40% 0

2000

4000

6000

8000

10000

00.511.522.53

Compressive Strength,

? (

kPa)

B/FA (%)

C/FA = 10%

C/FA = 15%

C/FA = 15%

56 Days

W/FA=40%

36

(a) (b)

(b) (d)

Figure 5.5Effect of mix ratio on compressive strength of geomaterial with C/FA ratio

at W/FA ratio 50% for (a) 7 days, (b) 14 days, (c) 28 days and (d) 56 days

0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Strength,

? (

kPa)

B/FA (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

7 Days

W/FA = 50% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Strength,

? (

kPa)

B/FA (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

14 Days

W/FA = 50% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Strength,

? (

kPa)

B/FA (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

28 Days

W/FA = 50% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Strength,

? (

kPa)

B/FA (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

56 Days

W/FA = 50%

37

5.4 Effect of curing on compressive strength of geomaterial

Figures 5.6 and 5.7 represent the relationship between compressive strength

with age of curing of specimens for W/FA ratios of 40% and 50% respectively. It is

observed that the effect of curing decreases with increase in B/FA ratio. This may

happen due to increase in volume of beads in mix proportion where the water

absorption capacity of EPS material is almost negligible. Increase in beads content

The relationship shows increase in value of compressive strength almost linearly upto

28 days curing period however, it decreases from 28 to 56 days. Effect of curing

beyong 28 days is found to have very less increase in compressive strength.

The effect of increase in compressive strength is significant with increase in

C/FA ratio and W/FA ratio. With increase in C/FA ratio from 10 to 20% almost

double increase in value of compressive strength is observed for same configuration.

Similarly, increase in value of W/FA ratio decreases the compressive strength. With

nearly 10% increase in value of C/FA ratio decreases the compressive strength by 15

– 26% for the same configuration of B/FA ratio.

Therefore, it can be stated that all the three mix ratios affect significantly in

terms of curing period on strength.

38

(a) (b)

(b) (d)

(e)

Figure 5.6 Effect curing period on compressive strength of geomaterial with C/FA

ratio at W/FA ratio 40% for B/FA ratios (a) 0.5%, (b) 1.0%, (c) 1.5%, (d) 2.0 % and

(e) 2.5% 0

2000

4000

6000

8000

10000

0714212835424956

Compressive Strength, ? (kPa)

Curing Period (Days)

B/FA = 0.5%C/FA=10%

C/FA=15%

C/FA=20% 0

2000

4000

6000

8000

10000

0714212835424956

Compressive Strength, ? (kPa)

Curing Period (Days)

B/FA = 1.0%C/FA=10%

C/FA=15%

C/FA=20% 0

2000

4000

6000

8000

10000

0714212835424956

Compressive Strength, ? (kPa)

Curing Period (Days)

B/FA = 1.5%C/FA=10%

C/FA=15%

C/FA=20% 0

2000

4000

6000

8000

10000

0714212835424956

Compressive Strength, ? (kPa)

Curing Period (Days)

B/FA = 2.0%C/FA=10%

C/FA=15%

C/FA=20% 0

2000

4000

6000

8000

10000

0714212835424956

Compressive Strength, ? (kPa)

Curing Period (Days)

B/FA = 2.5%C/FA=10%

C/FA=15%

C/FA=20%

39

(a) (b)

(b) (d)

(e)

Figure 5.7 Effect curing period on compressive strength of geomaterial with C/FA

ratio at W/FA ratio 50% for B/FA ratios (a) 0.5%, (b) 1.0%, (c) 1.5%, (d) 2.0 % and

(e) 2.5%

0

1000

2000

3000

4000

5000

0714212835424956

Compressive Strength, ? (kPa)

Curing Period (Days)

B/FA = 0.5%C/FA=10%

C/FA=15%

C/FA=20% 0

1000

2000

3000

4000

5000

0714212835424956

Compressive Strength, ? (kPa)

Curing Period (Days)

B/FA = 1.0%C/FA=10%

C/FA=15%

C/FA=20% 0

1000

2000

3000

4000

5000

0714212835424956

Compressive Strength, ? (kPa)

Curing Period (Days)

B/FA = 1.5%C/FA=10%

C/FA=15%

C/FA=20% 0

1000

2000

3000

4000

5000

0714212835424956

Compressive Strength, ? (kPa)

Curing Period (Days)

B/FA = 2.0%C/FA=10%

C/FA=15%

C/FA=20% 0

1000

2000

3000

4000

5000

0714212835424956

Compressive Strength, ? (kPa)

Curing Period (Days)

B/FA = 2.5%C/FA=10%

C/FA=15%

C/FA=20%

40

5.5 Failure pattern

The failure patterns of the lightweight geomaterial are also studied under

compressive loading condition. It was observed that the failure patterns of test

specimens were highly influenced by all the three mix ratios used for preparation of

lightweight geomaterial.

As B/FA ratio increases the failure pattern of test specimen changes from

brittle to ductile behavior. This can also be confirmed by stress-strain curves plotted

for different test specimen. However, increase in C/FA ratio changes the failure

pattern from ductile to brittle behavior. Most of the test specimen were failed along

the diagonal of the cube. The ductile and brittle behavior of failure patterns are

depicted in Figures 5.8 and 5.9 respectively.

Figure 5.8(a) Test specimen of geomaterial failed under compressive load

(Ductile behavior)

Figure 5.8(b) Test specimen of geomaterial failed under compressive load

(Brittle behavior)

41

5.6 Stress-strain behavior

The data obtained from compressive strength test was also used to plot the

stress-strain curve and to determine stiffness characteristics of lightweight

geomaterial. With increase in C/FA ratio the test specimen becomes more brittle. The

specimens of geomaterial failed within a strain range of 1 to 2%. The compressive

strength and stress-strain behavior of geomaterial are affected by B/FA ratio. The

compressive stress is decreased with increase in B/FA ratio for 7, 14, 28 and 56 days

cured specimens. It can also be seen that the compressive strength and stress-strain

behavior is significantly affected by W/FA ratio. With increasing W/FA ratio, the

compressive strength as well as stiffness of EPGM decreased and the stress-strain

curves become more ductile. Therefore, it can be stated that, all three mix ratios have

significant effect on compressive strength and stiffness characteristics of geomaterial.

The stress-strain curves for different mix proportions for different curing

periods are shown in Figures 5.9 and 5.10.

42

(a) (b)

(c) (d)

(e) (f)

(g) (h) 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress,

?c(kPa)

Axial Strain, ?(%)

C/FA=10%

C/FA=15%

C/FA=20%

7 Days

W/FA=40%

B/FA=0.5% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

14 Days

W/FA=40%

B/FA=0.5% 0

2000

4000

6000

8000

10000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

28 Days

W/FA=40%

B/FA=0.5% 0

2000

4000

6000

8000

10000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

56 Days

W/FA=40%

B/FA=0.5% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA=10%

C/FA=15%

C/FA=20%

7 Days

W/FA=40%

B/FA=1.0% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

14 Days

W/FA=40%

B/FA=1.0% 0

2000

4000

6000

8000

10000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

28 Days

W/FA=40%

B/FA=1.0% 0

2000

4000

6000

8000

10000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

56 Days

W/FA=40%

B/FA=1.0%

43

(i) (j)

(k) (l)

(m) (n)

(o) (p) 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c (kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

7 Days

W/FA=40%

B/FA=1.5% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

14 Days

W/FA=40%

B/FA=1.5% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

28 Days

W/FA=40%

B/FA=1.5% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

56 Days

W/FA=40%

B/FA=1.5% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA=10%

C/FA=15%

C/FA=20%

7 Days

W/FA=40%

B/FA=2.0% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

14 Days

W/FA=40%

B/FA=2.0% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

28 Days

W/FA=40%

B/FA=2.0% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

56 Days

W/FA=40%

B/FA=2.0%

44

(q) (r)

(s) (t)

Figure 5.9 Stress-strain curves for different C/FA ratios for W/FA ratio 40%

0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA=10%

C/FA=15%

C/FA=20%

7 Days

W/FA=40%

B/FA=2.5% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

14 Days

W/FA=40%

B/FA=2.5% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

28 Days

W/FA=40%

B/FA=2.5% 0

2000

4000

6000

8000

10000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

56 Days

W/FA=40%

B/FA=2.5%

45

(a) (b)

(c) (d)

(e) (f)

(g) (h) 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress,

?c(kPa)

Axial Strain, ?(%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

7 Days

W/FA = 50%

B/FA = 0.5% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

14 Days

W/FA = 50%

B/FA = 0.5% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

28Days

W/FA = 50%

B/FA = 0.5% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

56 Days

W/FA = 50%

B/FA = 0.5% 0

500

1000

1500

2000

2500

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

7 Days

W/FA = 50%

B/FA = 1.0% 0

500

1000

1500

2000

2500

3000

3500

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

14 Days

W/FA = 50%

B/FA = 1.0% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

28 Days

W/FA = 50%

B/FA = 1.0% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

56 Days

W/FA = 50%

B/FA = 1.0%

46

(i) (j)

(k) (l)

(m) (n)

(o) (p) 0

500

1000

1500

2000

2500

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

7 Days

W/FA = 50%

B/FA = 1.5% 0

500

1000

1500

2000

2500

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

14 Days

W/FA = 50%

B/FA = 1.5% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

28 Days

W/FA = 50%

B/FA = 1.5% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

56 Days

W/FA = 50%

B/FA = 1.5% 0

500

1000

1500

2000

2500

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

7 Days

W/FA = 50%

B/FA = 2.0% 0

500

1000

1500

2000

2500

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

14 Days

W/FA = 50%

B/FA = 2.0% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

28 Days

W/FA = 50%

B/FA = 2.0% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

56 Days

W/FA = 50%

B/FA = 2.0%

47

(q) (r)

(s) (t)

Figure 5.10 Stress-strain curves for different C/FA ratios for W/FA ratio 50%

0

500

1000

1500

2000

2500

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

7 Days

W/FA = 50%

B/FA = 2.5% 0

500

1000

1500

2000

2500

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

14 Days

W/FA = 50%

B/FA = 2.5% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

28 Days

W/FA = 50%

B/FA = 2.5% 0

1000

2000

3000

4000

5000

00.511.522.53

Compressive Stress, ?

c(kPa)

Axial Strain, ? (%)

C/FA = 10%

C/FA = 15%

C/FA = 20%

56 Days

W/FA = 50%

B/FA = 2.5%

48

As discussed earlier, the specimen with B/FA as 0.5% have compressive

strength values more than specimen without beads. This is due to the presence of

highly compressible beads in suitable mix proportion where specimen carried higher

load with stain 1.5% compared to specimen without beads which failed with less load

having strain 1.0%. With little more strain value geomaterial having beads can solve

specific purposes whenever required with higher compressive strength. Figures 5.11

(a) and (b) represents the nature of stress-strain curves observed for such condition.

(a)

(b)

Figure 5.11 Stress-strain curves for different B/FA ratios for W/FA ratio

(a) 40% and (b) 50% 0

1000

2000

3000

4000

00.511.522.53

Compressive Strength (kPa)

Axial Strain, ?(%)

C/FA = 20%, W/FA = 40% ; 7 Days

B/FA = 0%

B/FA = 0.5%

B/FA = 1.0%

B/FA = 1.5%

B/FA = 2.0%

B/FA = 2.5% 0

1000

2000

3000

4000

00.511.522.53

Compressive strength (kPa)

Axial Strain, ?(%)

C/FA = 20% ; W/FA = 50% 7 Days

B/FA = 0%

B/FA = 0.5%

B/FA = 1.0%

B/FA = 1.5%

B/FA = 2.0%

B/FA =2.5%

49

5.7 Initial tangent modulus

Initial tangent modulus is an important property of lightweight geomaterial

which gives an idea about the stiffness of material. The stiffness of geomaterial is

determined by calculating initial tangent modulus as the slope of stress-strain curve

from origin. This stiffness of geomaterial is highly influenced by C/FA ratio. Higher

the compressive strength of test specimen higher is stiffness values. For the specimen

tested for different curing period, the values of initial tangent modulus are found to be

in the range of 112 -2800 MPa. The relationship between compressive strength and

initial tangent modulus is well established by fitting a curve as shown in Figure 5.12.

These values of initial tangent modulus are higher as compared with earlier developed

geomaterial using EPS beads with nearly same density range.

Figure 5.12 Relationship between compressive strength and initial tangent modulus of

geomaterial

The initial tangent modulus values of lightweight geomaterial are much higher

as compared to values reported in earlier studies of lightweight geomaterial. The

comparison between properties of lightweight geomaterial developed earlier (Liu, et

al; 2006, Padade and Mandal 2014) and geomaterial developed in the present study is

given in Table 5.1.

y = 0.405x + 397.8

R² = 0.778

0

1000

2000

3000

4000

5000

0200040006000800010000Initial Tangent Modulus (kPa)

Compressive Strength (kPa)

50

Table 5.1 Comparison of geomaterial properties with earlier developed products

Property

Lightweight fill

material

Expanded

polystyrene-based

geomaterial with fly

ash

Lightweight

geomaterial

developed in

present

study (Liu et al., 2006) (Padade

andMandal,2014)

Density

(kg/m3) 700 – 1100 725 – 1320 772 – 1361

Compressive strength

(kPa) 100 – 510 158 – 3290 171- 8555

Initial tangent modulus

(MPa) 79 – 555 51-500 112 -2800

CHAPTER 6

CONCLUSIONS

6.1 General

The engineering properties of proposed expanded polystyrene based

geomaterial are investigated through a laboratory experimental study. The lightweight

geomaterial prepared with EPS beads, fly ash and cement using different mix ratios

between beads to fly ash, cement to fly ash and water to fly ash. The effect of these

mix ratios on density, compressive strength and initial tangent modulus of this

geomaterial is presented. The following conclusions are drawn from the study and

summarized hereunder:

6.2 Conclusions

The lightweight geomaterial developed in the present study reveals various

properties and its application in various geotechnical engineering applications. The

density of lightweight geomaterial decreases with increase in B/FA ratio and W/FA

ratio. However, the effect of C/FA rati o is insignificant. Compressive strength of

geomaterial decreases with increase in B/FA ratio and W/FA ratio and it increases

with increase in C/FA ratio. Effect of curing beyong 28 days is found to have very

less increase in compressive strength. Strength and stifness characteristics are well co-

related in the study which gives an idea about the material and its application for

specific purpose.

6.3 Limitations of the study

Some of the limitations of the present study are given hereunder:

1. Control of weight of beads is very important in the present study which may not

be possible at every place. However, accurate weight is maintained while

preparation of test specimen in this study.

2. Threshold value of the geomaterial developed in the present study cannot be

specified.

6.4 Future Scope of work

The study can be repeated for cylindrical samples with varying aspect ratios.

52