civil miniproject vamshikrishna

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ROLE OF FLY-ASH IN CONSTRUCTION

A Mini project report submitted in partial fulfilment of the

Requirement for the award of the degree of

BACHELOR OF TECHNOLOGY

IN

CIVIL ENGINEERING

SUBMITTED BY

T.SURYA VAMSHI 08241A0150

V.VAMSHI KRISHNA 08241A0154

DEPARTMENT OF CIVIL ENGINEERING

GOKARAJU RANGARAJU INSTITUTE OF ENGINEERING

AND TECHNOLOGY

(Affiliated JNTUH, Hyderabad)

Bachupally, Nizampet Road, Kukatpally, Hyderabad-500090.

july 2011

DECLARATION

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We declare that this project entitled ROLE OF FLYASH IN CONCRETE has

been done by us and has not previously formed as the basis for the awards of any

degree or diploma or the similar title in this or any other institution.

T.SURYA VAMSHI 08241A0150

V.VAMSHI KRISHNA 08241A0154

ACKNOWLEDGEMENT

The satisfaction and euphoria that accompany the successful completion of any task

would be incomplete without the expression of appreciation of simple matter to the

people who made it possible because success is epitome of hard work, cogency for

fulfillment of the mission, indefatigable perseverance and most of all those whose

guidance and encouragement had made successful in winding up this opus.

We express our profound feeling of gratitude to prof. Dr. Venkat Ramana,

Head of the department, Civil Engineering, Gokaraju Rangaraju Institute of

Engineering And Technology for his constant words of encouragement and concrete

suggestions which helped us in completion of this project.

We would like to express our sincere thanks to M/S Surasani Constructions

pvt. Ltd, for providing us an opportunity to complete our mini project successful,

which is a part of course curriculum. This training would not have successfully

completed without the guidance and support to Mr. M. Sridhar Reddy

(Project Manager), Mr. C. Praveen Kumar(Site Engineer) and the entire project

team. We are deeply indebled to the project team members who were always ready to

help us during project time.

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ABSTRACT Fly ash is a fused residue of clay minerals present in coal. The high temperature generated when coal burns in thermal power plants, transforms the clay minerals in coal powder into a

variety of fused fine particles of mainly aluminium silicate composition.

Fly ash can be used in Portland cement concrete to enhance the performance of the concrete. Fly ash can be used for construction of road and embankment. This utilization

has many advantages over conventional methods. Fly ash is most commonly used as a

pozzolan in PCC applications.

Fly Ash Contributes to Concrete Durability and Strength

Durability is the ability to maintain integrity and strength over time. Strength is only a

measure of the ability to sustain loads at a given point in time. Two concrete mixes with equal

cylinder breaks of 4,000 psi at 28 days can vary widely in their permeability, resistance to

chemical attack, resistance to cracking and general deterioration over time all of which are

important to durability. Cement normally gains the great majority of its strength within

28 days, thus the reasoning behind specifications normally requiring determination of 28-day

strengths as a standard. As lime from cement hydration becomes available (cements tend to vary widely in their reactivity), it reacts with fly ash. Typically, concrete made with fly ash

will be slightly lower in strength than straight cement concrete up to 28 days, equal strength at

28 days, and substantially higher strength within a years time. Conversely, in straight cement concrete, this lime would remain intact and over time it would be susceptible to the effects of

weathering and loss of strength and durability.

Company details: We are hereby making our project in M/S Surasani Constructions pvt. Ltd to successfully complete our project as per standard specification.

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CONTENTS

1. INTRODUCTION

1.1 General

1.2 Use of fly ash in concrete

1.2.1 Fly ash effects in concrete

1.3 Objectives

1.4 Scope of work

2. LITERATURE REVIEW

2.1 General

2.2 Characteristics of fly ash

2.2.1 Physical Properties Of Fly Ash 2.2.2 Chemical Compositions Of Fly Ash 2.2.3 Morphology Of Fly Ash 2.2.4 Mineralogy of Fly Ash

2.3 High content of fly ash in concrete

2.4 Role of water in concrete:

2.5 Influence of Fly Ash on Water Content

2.6 High range water-reducers

2.6.1 Composition

2.6.2 Mechanism of Action

2.6.3 Effects Fresh State

2.6.3.1 Fresh concrete

2.6.3.2 Hardened State

2.6.3.3 Volume Change

3. DESIGN OF CONCRETE MIX

3.1 General

3.2 Material selection

3.2.1 Cement

3.2.2 Fly-Ash

3.2.3 Sand

3.2.4 Coarse Aggregate

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3.2.5 Water

3.2.6 Super-plasticizer

3.3 Mixture proportioning procedure

3.4 Calculation of mix proportions

4. EXPERIMENTAL WORK

4.1 GENERAL

4.2 Planning

4.3 Estimation of required material

4.4 Procurement of material

4.5 Preliminary laboratory tests

4.6 Preparation and casting of test specimen

4.7 Mixing procedure

4.8 Compaction of test specimen

4.9 Specimen conditioning and testing

5. TEST RESULTS AND DISCUSSION

5.1 General

5.2 Test results

5.2.1 Properties of fresh concrete

5.2.2 Properties of hardened concrete

6. CONCLUSION

7. BIBILOGRAPHY

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INTRODUCTION

1.1 GENERAL

Cement is the most costly and energy-intensive component of concrete. The unit cost

of concrete can be reduced by partial replacement of cement with fly ash. The

disposal of fly ash is one of the major issues for environmentalists, as dumping of fly

ash as waste material causes severe environmental problems. The utilization of fly ash

instead of dumping it as a waste material can be partly used on economic grounds as

pozzuolana for partial replacement of cement and partly because of its beneficial

effects of lower water demand for similar workability, reduced bleeding and lower

evolution of heat. It has been used particularly in mass concrete applications and large

volume placement to control expansion due to heat of hydration and also helps in

reducing cracking at early ages.

The proportion of fly ash used as a cementitious component in concrete depends on

several factors. The design strength and workability of concrete, water demand and

relative cost of fly ash compared with cement are particularly important in mixture

proportioning of concrete. One of the major developments in the area of fly ash

utilization in concrete has been the technology of high-performance, high-volume fly

ash concrete by Malhotra and Ramezanianpour [1] and Malhotra [2]. High fly ash

concretes with fly ash/cementitious ratio up to 75% (by mass) and an

aggregate/cement ratio of 6 have compressive and flexural strengths that are more

than adequate for lean concrete base or subbase application in pavement structure [3].

Concrete containing 50% replacement by mass of class F fly ash can be designed to

have 1- and 28-day cube strengths of 20 and 60 MPa, respectively [4]. High-volume

fly ash concrete has adequate early-age and later-age strength developments and

considerably lower temperature rise, and its applications should have a water content

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of not less than 115 kg/m3 and a sufficient amount of a retarded version of

superplasticizer to maintain satisfactory slump and placing characteristics [5].

1.2 USE OF FLY ASH IN CONCRETE

It has been above 70 years to research and use fly ash. With its application, the action

mechanism of fly ash had been recognized. During the initial stage, only its

pozzolanic activity is paid attention [8 and 9]. Many researchers devoted themselves

to the research of the potential activity of fly ash and the hydration process of fly ash

cement. With the deepening of the cognition for fly ash properties, some people found

that the particles of fly ash have the morphology that is different to other pozzolanic

materials. It is the unique particle morphology to make it have the ability reducing

water, which other pozzolanic materials do not have [10, 11, 12 and 13]. It influences

not only the rheological property of fresh mortar but also the initial structure of

hardened cement stone. In the end of 1970s, Jan de Zeeuw and Abersch [14] put

forward that the role of fly ash, which its particle size is less than 30 , may be similar

to that of the micro-particle of unhydrated cement in cement stone. In 1981, Danshen

and Yinji [15] and Danshen [16] summarized the previous research results and put

forward the hypothesis of "fly ash effects." They considered that fly ash has three

effects in concrete, i.e., morphological, activated and micro aggregate effects. The

three effects are relative each other. This shows that the morphological effect is the

important aspect of fly ash effects.

The morphological effect means that in concrete, mineral-powdered materials produce

the effect due to the morphology, structure and surface property of the particle and the

particle size distribution. From the influence of fly ash on the properties of cement-

based materials, the morphology effect includes three aspects: filling, lubricating and

well distributing. These roles depend on the shape, size distribution, etc., of fly ash

and influence many properties of concrete.

The pozzolanic effect is the main effect of FA, which states that the unfixed SiO2 and

Al2O3 in FA can be activated by Ca(OH)2 product of cement hydration and produce

more hydrated gel. Since the gel produced from pozzolanic action can fill in the

capillary in concrete, it effectively contributes to concrete strength, especially in

concrete with high volume fly ash (often the generation of long-term strength is

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mainly from pozzolanic effect). Taking the cement hydration as prerequisite, the

contribution of pozzolanic effect to strength can also be regarded as one part of

cement contribution. It should also be pointed out here that the above three effects of

Fly ash infect co-affect with each other, but focus on the different performance of

concrete, respectively. Since it is difficult and not necessary to distinguish the

previously mentioned three effects, often they are collectively called "fly ash effect"

or "pozzolanic effect.

Roller-compacted concrete (RCC), a kind of widely used pavement material, is a sort

of super-dry concrete with high density and high strength, resulting from its low water

demand and formation by vibration and rolling. Incorporating FA into RCC to make

RCC with fly ash (FRCC) can further reduce the cost and meanwhile specifically

improve the performance. The specific improvement lies in the following aspects: (1)

Incorporating FA by the method of super-substituting, a widely used design method,

effectively increases the total amount of binder in RCC and makes it easier to

compact. (2) Substituting Fly Ash for a part of cement in RCC can remarkably

decrease the quantity of heat produced by cement hydration. (3) Formation by

vibration and rolling, and also by its required low water-cement ratio, can somehow

make up the early age strength of FRCC, which is often cut down by the incorporation

of a large amount of FA in ordinary concrete. With the previously mentioned

advantages, FRCC is gradually extended in pavement construction. Possessing so

many favourable properties, amount of Fly Ash in FRCC can further be promoted and

the performance of pavement can still be guaranteed, while taking rational ratio

design as prerequisite.

1.2.1 Fly Ash effects in concrete

Following are the effects which was found out in roller compacted concrete with high

content of class F fly ash:

1. Since the pozzolanic reaction between FA and cement lags behind cement

hydration, High Fly ash Roller Compacted Concrete (HFRCC) strength at early

curing age is poor and decreases with increasing FA content.

2. Following the curing age, greater amounts of FA are activated and cause the

strength of HFRCC to continuously develop.

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3. Incorporating fly ash by high content and super-substituting method makes

HFRCC easier to compact, and together with the amount of crystal phase Ca(OH)2

and harmful pore reduction, HFRCC at long-term curing age becomes dense and

homogeneous. These improved properties are more beneficial to flexural strength,

which is more sensitive to inner structure characteristic than compressive strength.

Fig.1.1: SEM micrographs (8,000) of Portland cement (a) and low-calcium fly ash

(b)

1.3 OBJECTIVES

In this project work, objective is to develop engineering database on the mechanical

properties and to determine the necessary level of fluidity, generally termed as

workability (as control of workability is one of the main objectives of mixture

proportioning) of fly ash concrete incorporating VTPS fly ash and Ordinary Portland

Cement, and it is compared with controlled concrete.

Also four grades (M20, M25, M30 and M35) of concrete are targeted to select

optimum percentage of cement replacement by fly ash as cementitious material, for

obtaining maximum possible 28 days compressive strength.

To evaluate the dose of superplasticizer for the same water-cement ratio of each grade

of concrete to increase the slump value from 80-120mm.

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1.4 SCOPE OF WORK

The scope of project work is as under:

Literature review regarding requirements of fly ash, material properties and

characteristics of high performance concrete.

1. Preliminary laboratory test of fine aggregates, coarse aggregate for mix

design.

2. Mix design and proportioning for ingredients.

3. Modification and correction in mix proportioning during concrete production

to meet workability requirement.

4. Modification and correction in mix proportioning during concrete productions

for moisture content of fine aggregates.

5. Water to binder (cement plus fly ash) ratio was kept 0.50,0.46,0.42 and 0.38

for M20, M25 ,M30 and M35 grade concrete respectively.

6. 150 mm size cubes were casted, cured in water tank and weighed for unit

weight before compression testing for the determination of mechanical

properties of concretes at 7 days and 28 days .

7. Superplasticizer dose was calculated for each grade of concrete for same W/C

ratio to obtain slump value 80-120mm.

8. Test result interpretation for optimum selection of suitable part replacement of

fly ash as cementitious material.

9. Compressive strength test and analysis for the determination of mechanical

properties of concretes at 7 days and 28 days from the date of casting of the

test specimen.

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LITERATURE REVIEW

2.1 GENERAL

Fly ashes from Vijayawada thermal power plants were used in the experiments

of the present study.. A brief review of literature about the physical and chemical

properties; mineralogy and morphology behavior of fly ashes is presented. Literatures

regarding concrete applications of fly ashes have been used in construction are also

discussed.

Fly ash is produced from burning of pulverized coal in thermal power

plants. The pulverized coal is fed into the boilers and burnt with the supply of

additional air. The temperature in the boiler exceeds 1600 C and the most of the

mineral matter present in the coal are fused and altered physically and chemically.

The resulting residue is called coal combustion by-products namely bottom ash,

economizer ash, air pre-heater ash, and electrostatic precipitator ash (fly ash). These

ashes are handled and disposed off separately owing to their differing qualities by

mechanical, hydraulic and pneumatic conveying systems. The quality of ash produced

is dependent on various factors like source coal and its degree of pulverization, design

of furnace, changes in coal supply, changes in boiler load, and firing condition.

Because of this inherent variability of the material, it is necessary to study the

characteristics and engineering behavior of fly ash in detail before its use in an

application.

Fly ash is a promising and economical alternative material to construction engineering

applications. Review of literature shows that fly ash has been utilized in the

construction of pavement construction, in high strength concrete, high performance

concrete and in other applications.

A. CHARACTERISTICS OF FLY ASH

As per ASTM C 618 1993[17], there are two classes of fly ash namely class F and

class C. Class F fly ash is produced from burning anthracite or bituminous coal and is

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pozzolanic in nature and class C is obtained from lignite or sub-bituminous coal.

Class C fly ash possesses both pozzolanic and self-hardening property. Hence, it is

necessary to characterize the material scientifically to utilize it in different

applications.

i. Physical Properties Of Fly Ash

The specific gravity, loss on ignition (LOI) and specific surface area are the prominent

physical properties of fly ashes. The specific gravity of fly ash may vary from 1.3 to

4.8. The iron oxide content plays a decisive role in the specific gravity of the material.

The specific gravity is more for fly ashes containing more iron oxide and vice versa.

The presence of opaque spherical magnetite and hematite particles in sufficient

quantity will increase the value of specific gravity to about 3.6 to 4.8. On the other

hand, as the amount of quartz and mullite increases, the specific gravity decreases.

However, coal particles with some minerallic impurities will have lower specific

gravity in the range 1.3 to 1.6. The range of specific gravity of Canadian fly ashes is

reported to be in the range of 1.91 to 2.94 and that of American fly ashes in the range

of 2.14 to 2.69.

Dayal and Sinha (1999) [18] have reported the specific gravity of Indian coal ashes

to range between 1.94 and 2.34 with a mean value of 2.16 and standard deviation of

0.21. The specific gravity of fly ash decreases as the particle size increases. The

specific gravity increases when the fly ash particles were crushed. Typical values of

the specific surface of Indian fly ashes (3267 to 6842 cm2/g) were comparable with

that of the foreign ashes (2007 to 6073 cm2/g).

ii. Chemical Compositions Of Fly Ash

The main chemical compounds of class F fly ash are silica, alumina and iron oxide.

Other minor constituents include oxides of calcium, magnesium, titanium, sulphur,

sodium and potassium. Class C fly ash contains relatively higher proportion of

calcium oxide and lesser proportion of silica, alumina and iron oxide than class F fly

ash. Typical chemical compositions of various Indian fly ashes are summarized in

Table 2.2.

iii. Morphology Of Fly Ash

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Fly ash is a heterogeneous material; with the degree of heterogeneity persisting at all

levels viz macro, micro and nano structural levels (Sun Wei at al 2003)[51]. By using

scanning electron microscopy and energy dispersive X-ray analysis (EDXA)

technique the particle shape and surface characteristics of fly ash can be studied.

Some of the particles are hollow and spherical, which are termed as cenospheres

[Fig2.1 (a)].. These cenospheres are also called floaters, as they are light in weight.

Fly ashes contain small spherical particles within a large glassy sphere, called

plerospheres [Fig. 2.1 (b)]. In some particles, where regions of a spherical particle

melted or eroded away are known as clathrosphere [Fig. 2.1 (c)]. This indicates the

intense chemical activity having occurred within the particles in the furnace zone

during the short residence time. The exterior surfaces of solid and hollow spherical

particles of low calcium oxide fly ashes are generally smoother than the high calcium

oxide fly ashes, which may have surface coatings of materials rich in calcium1. In

some fly ashes small sub-micron size particles may be sticking to the large spherical

particles, due to the convexity of the surfaces. The studies conducted by Mehta

(1998)[19] on low calcium fly ashes (CaO

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Fig. 2.1 Scanning electron micrographs of inhomogeneous spherical particle

types of fly ashes (a) cenosphere (b) plerosphere And (c) clathrosphere

(Hemmings and Berry, 1987)

Diamond 1986[20] studied the particle morphologies of 13 low calcium fly ashes

collected from Indiana. The salient features of the study are as follows.

The fly ash contained spherical particles of wide size range about 1 m to more

m with smooth surface. Some of the particles were covered with surface

irregularities or deposits.

Presence of plerospheres (Thin walled hollow spheres with smaller included

spheres) and non-spherical particles were identified.

The interior structure of a particle revealed the presence of iron rich magnetic

grain on a sphere and in the adjacent sphere needle shaped particles of mullite

crystals were present.

Presence of heterogeneous structure of particles contained within a plerosphere

was also identified.

Plate like structures that constitute the surface of a sphere was also present

occasionally. These structures may represent the magnetic plate.

Garg (1995)[21] studied the morphology of Indian fly ashes. The fly ashes contained

angular as well as rounded black particles, spheroid glass, and minute silica grains.

Sharma (1993)[22] has classified Indian fly ashes based on the shape of particles as

one of the parameters. According to him group- fly ashes contained mainly spherical

particles with the size range between 2-25 m. The surfaces of glassy spheres in this

group are predominantly smooth without any deposit, only some adherence was

observed.

Group- fly ashes contained a wide range of particles (2-35 m). Most of the particles

were spherical in shape, but some sintering and surface depositions were also

observed.

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Where as group- fly ashes which were of low reactive type contained mostly

irregularly shaped and relatively coarser particles, which have undergone probably

little or no fusion in the combustion process.

2.2.4 Mineralogy of Fly Ash

Fly ash consists of both crystalline and amorphous phases. The crystalline phases

could be quartz, mullite, silimanite, crystallite, cristobalite, sulphates of iron,

magnetite etc. The amorphous phases could be of silica and silicates predominantly of

aluminium but containing calcium, magnesium, and iron in varying concentration

with and without traces of sodium and potassium.

The reactivity of fly ashes depends on the non crystalline or glass content in it. The

chemical composition of the glass in the high calcium fly ash is different from the low

calcium fly ash and hence the reactivity of both the ashes are different. The high

calcium fly ashes are more reactive than low calcium fly ashes. Diamond (1986)[20]

and Mehta (1998)[19] pointed out that the composition of glass in low calcium fly

ashes is different from high calcium fly ashes. Typically low calcium fly ashes show a

diffused halo with maxima at 2 = 21-25 and high calcium fly ashes at 30-34 .

Garg (1999)[23] conducted XRD studies of Indian fly ashes and the crystalline

constituents identified were quartz (SiO2), mullite (3 Al2O3. 2SiO2), hematite (Fe2 O3)

and magnetite (Fe3 O4).

The minerals present in fly ash obtained from Koradi thermal power plant (Nagpur)

were quartz low (syn) most predominant, mullite- predominant, brookite, sillimanite

and ferroselite (Gangadhara Rao et al. 1998)[24].

As reported by Garg (1999)[23] mentioned that quartz and mullite were the main

crystalline constituents in British fly ashes and the American fly ashes contained

magnetite and hematite in large proportions. The range of quantitative measurement

in British fly ashes was quartz (1-6.5%); mullite (935%); magnetite and hematite

(5% or less). For American fly ashes the proportions were quartz (0 - 4%); mullite (0

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16%); magnetite (030%); and hematite (18%). The glass proportions in these fly

ashes were found to range from 50 to 90%.

b. HIGH CONTENT OF FLY ASH IN CONCRETE

Poon, C.S.,et al.(2002)[25] Low calcium fly ash (ASTM Class F) has been widely

used as a replacement of cement in normal and high strength concrete. In normal

strength concrete, the replacement level can be more than 50%, while in high strength

concrete, the replacement level is usually limited to 15 25%. The main objectives of

using fly ash in high strength concrete are to reduce heat generation and to obtain

better durability properties. However, in concrete mixes prepared at a low water-to-

binder (w/b) ratio, 20% fly ash content may not be sufficient to suppress the excessive

heat of hydration.

In a laboratory investigation carried out at the Hong Kong Polytechnic University, the

temperature in-crease due to cement hydration of large concrete blocks

(1000_1000_1000 mm) was measured. It was found that for 50 MPa concrete, a 25%

fly ash replacement reduced the maximum temperature of the concrete by 6C,

whereas for 100 MPa concrete, a 20% fly ash replacement did not result in a lower

temperature rise.

This seems to indicate that in concrete at a lower w/b ratio, the effect of a normal

amount of fly ash is not significant in reducing the temperature rise due to cement

hydration.

In the past, concrete containing high volumes of low-calcium fly ash was mostly used

in mass concrete, e.g., roller compacted dams and highway base courses [3], where

high strength and high degree of workability were not required. High volume fly ash

concrete for structural use was developed by the Canada Centre for Mineral and

Energy Technology (CANMET) in 1985]. This type of concrete has typically 5060%

fly ash as the total cementitious materials' content. Superplasticizers (high-range

water reducing admixtures) are used to obtain a high degree of workability.

Successful applications of this type of concrete included concrete columns with a

compressive strength requirement of 50 MPa at 120 days, and piles with the

compressive strength requirement of 45 MPa at 28 days.

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It is known that fly ashes generally have negative effects on the concrete strength,

particularly at early ages [6]. Using large quantities of this material in concrete seem

to be in contradiction to the original aims of preparing high strength concrete.

However, as observed by many researchers [79], fly ash concrete may have better

strength performance when they are prepared at lower w/b ratios. At a w/b = 0.5, a

45% fly ash replacement resulted in about 30% reduction in 28-day compressive

strength, but at a w/b = 0.3, the strength reduction was reduced to 17%. Also, the

advances of concrete admixture technology allow concrete mixtures to be prepared

with lower w/b ratios. It is therefore believed that high strength concrete can be

obtained with large volumes of fly ash.

The generation of fly ash and its use in India along with other countries is given in

Table 2.1. In India, generally Class F type fly ash is found. The chemical [36]

requirement of chemical composition for class C and Class F type ash in various

countries is shown in Table 2.2.

c. ROLE OF WATER IN CONCRETE:

Before water is added, however close the solid particles are, there is always some

space in the system. After water is added, a part of water is filled into these spaces,

which is called as filling water. Other water forms the layer of water on the surface of

the solid particle, which is called as the layer water. Because of the adsorption of the

solid surface to water molecule, the part of water that is closer to the surface of solid

will be restrained by solid particle and is not able to move freely. The water may be

called as the adsorpted layer water. The layer water that is not restrained by solid

particle is called as the free layer water. Mixing water is the sum of filling water,

adsorpted layer water and free layer water.

In the flow process of fresh mortar, filling water does not contribute to the fluidibility

because it only fills in the space and cannot make the particles separate to decrease

the moving resistance of particle. Of course, the filling water is able to move freely,

but the fluidity of fresh paste means that cement particles move with water under the

action of water. If only the water moves but the cement particle does not, it is not the

fluidity of cement paste but the separation.

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Table 2.2: Chemical requirement for fly ash in different countries

Country Germany Australia Austria Canada Spain India Japan U.K. Turky URSS USA

Standard DIN AS ONORM Canada UNE IS JIS BS TS GOST ASTM

No. 1045 1129 B 3319 3-A23 3812 A6201 3892 639 6269 C 618

Type of Fly Ash - - - C F 1 2 - - - - C F

SiO2 min% - - - - - - 35 45 - 40 -

(SAF) min% - - - - - 70 70 70 - - 70 - 70 50

MgO min% - - - - - 5 5 5 - 4 5 5 5

SO3 min% 4 2.5 3.5 5 5 4 4 3 - 2.5 5 3 5 5

CaO max% - - - - - - - - - - - - -

LOI max% 5 8 7 6 12 12 7 12 5 7 10 10 12 6

Alkalies max% - - - - - - - 1.5 - - - - 1.5 1.5

Moist. Max% 1.5 - 3 3 3 3 - 1 0.5 3 - 3 3

1. In cement LOI =Loss on ignition

2. In concrete S = SiO2

A = Al2O3

F = fe2O3

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When fresh mortar flows, adsorpted layer water moves with solid particle. It shows

the property that a solid has. Thus, it does not contribute to the fluidibility too. In fact,

this water can be exchanged with other in cement paste. This is a dynamic balance. As

a part, the adsorbed layer water does not contribute to fluidity. But for any molecule

of water, it is uncertain because it may be in the adsorbed layer or the free layer. It can

be seen from these that only free layer water contributes to the fluidibility. In the flow

process, free layer water makes the particles separate each other. The effort between

particles decreases. Thus, if the shape of solid particles is not considered, in a certain

degree, the thicker the free water layer, the better the fluidibility is. Fig. 2.1 shows the

model of water action and their contribution to the fluidibility.

Fig. 2.2: The model of water action and their contribution to fluidibility.

In fresh mortar, the amount of filling water depends on the packing density of system.

The higher the packing density, the less the filling water is. The amount of adsorpted

layer water depends on the specific surface area and surface property of solid

particles. It is the product of the specific surface area and the thickness of the

adsorpted layer. The thickness of adsorpted layer depends on the water affinity of

solid particles. The thickness of free water layer depends on the amount of free layer

water and the specific surface of solid particles. Under the condition of same amount

of free layer water, the larger the specific surface of solid particles, thinner the free

water layer is. Of course, the increase of the amount of free layer water will increase

the thickness free water layer.

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2.5.1 Influence of Fly Ash on Water Content

The particle of fly ash is different from one of cement in particle size, specific surface

and particle shape. They will influence the distribution of water in fresh mortar. This

is the essential reason of the influence of the morphological effect on the fluidibility

of fresh mortar.

2 2.6 HIGH-RANGE WATER REDUCERS (SUPERPLASTICIZERS) 3 2.6.1 Composition

The high-range water reducers presently used in the market can be classified [26]

according to their chemical nature in the following main groups:

Beta-naphthalene sulphonate formaldehyde condensates;

Melamine sulphonate formaldehyde condensates;

Modified ligno-sulphonates;

Esters of sulphonic acids;

Salts of carboxylic/hydroxy carboxylic acids.

4 2.6.2 Mechanism of Action

The mechanism of actin of high-range water reducers is mainly based on their ability

to be adsorbed on the surface of cement particles and modify the rheological

behaviour of the cement matrix. The rate of adsorption of high-range water reducers

depends on the chemical and mineralogical composition of the cement, its fineness

and in that calcium aluminate adsorbs very rapidly the high-range water reducer

molecules, while calcium silicate in the first hours of hydration adsorbs only a lower

amount of the high-range reducers. The increase of workability can be correlated with

the following properties.

1. The value of zeta potential of the electric double layer that is formed on the

surface of the cement particles by the polar groups of adsorbed superplasticizer

chains [27].

2. The molecular weight of the super plasticizer.

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The rate of workability loss is correlated to the retardation produced on the hydration

of cement.

2.6.3 Effects

The different properties of concrete indicate the specific way of using the admixture

that produces the desired modification. It is intended that if use of the admixture is not

indicated, the corresponding way of using the admixture does not exert a particular

action on the specific property cited.

2.6.3.1 Fresh State

Unit Mass

Unit mass of concrete is usually increased when high-range water reducers are used.

Workability

superplasticizers dramatically increase the ability of concrete to flow.

a. Cohesion: Cohesion is largely improved by the use of high-range water

reducer as a consequence of the reduction of water in concretes.

b. Air content:Air content may be slightly increased, especially in the case of use

of high dosages of the admixtures as superplasticizers.

c. Slump loss:At the same initial workability, slump loss may be higher in

concretes with high-range water reducers than in concrete without admixture.

At the same water/cement ratio, slump loss of concrete with superplasticizers

may be higher or lower than the control concrete without admixture as a

function of the type of superplasticizers used.

d. Pumpability: Pumpability of concrete is improved by the use of

superplasticizers, as a consequence of the increase in workability, and due to

cohesion in case of use as high-range water reducers.

e. Segregation: Segregation decreases when the admixture is either used as a

high-range water reduced or as a superplasticizers, provided that an adequate

mix design of the concrete is done.

17

f. Setting state: Generally the admixture used as a superplaticizer mildly retards

the setting of concrete, while use, as a high-range water reducer at normal

dosage does not give significant retardation.

g. Plastic shrinkage: Plastic shrinkage cracking can be increased by the use of

high-range water reducers if the ambient conditions are such that evaporative

demands are greater than the reduced bleeding capacity of the high-range

water reduced concrete.

h. Bleeding: Bleeding is reduced by the use of high-range water reducers. If the

aggregate size distribution is not properly designed, bleeding can be increased

when superplasticizers is used.

2.6.3.2 Hardened State

a. Strength: The strength of concretes is considerably increased by the use of

high-range water reducers as a consequence of the reduction of the

water/cement ratio, while strength is not substantially modified in case of use

as a superplasticizers.

b. Porosity: Capillary absorption of concrete is directly linked to its capillary

porosity, which is influenced by the water/cement ratio, that can be largely

reduced by the use of the admixture as a high-range water reducer.

c. Freeze-thaw attack: High-range water reducers-superplasticizers normally

induce some air entrainment in the concrete mixes, but some of the air bubbles

introduced are than those of air entraining agents and therefore are not useful

to increase the freeze-thaw durability of concretes [28].

d. Attack by aggressive solutions: The resistance of concrete to attack, by

aggressive solutions is increased by high-range water reducers because of the

reduction of concrete capillarity porosity. The use of the admixture as

superplastisizer does not change the resistance of the concrete [28,29,30].

2.6.3.3 Volume Change

a. Creep: The use of high-range water reducers reduces creep due to the

reduction of the water/cement ratio of the concrete.

18

b. Drying shrinkage: The shrinkage of concrete is reduced by high-range water

reducers mainly because of the reduction of the water content of the concrete.

When a concrete is manufactured with the admixture used as a

superplasticizers. Its shrinkage, for the same percentage of moisture loss, has

been found [29] to be higher then in a concrete produced with the same

quantity of water but without the use of the superplasticizers. On the other

hand it has been also shown that with the same curing condition, the shrinkage

of a superplasticized concrete is similar to that of a corresponding plain

concrete.

The concrete can be drawn that the better dispersion of cement particles in a

superplasticized concrete produces a finer capillary under normal ambient conditions,

so that the shrinkage of superplasticized concrete is practically similar to that of a

normal concrete manufactured with the same amount of water.

19

DESIGN OF CONCRETE MIX

3.1 GENERAL

Following the preliminary laboratory tests of materials incorporated in the concrete,

the mix proportions were selected to ensure the workability and surface finishes of

fresh concrete and shall have the required strength (not less then the target mean

strength, and durability, when hardened).

As stated earlier Mix Designing Methods according to Indian Bureau of Standard is

adopted as a general guideline along with the field experience of Project Guide for

this work programme to arrive at mix proportioning for four grade of concrete (M20,

M25,M30 and M35) with superplasticizer.

3.2 MATERIAL SELECTION

For the development of concrete in the laboratory, materials used were ordinary

Portland cement, fly ash, fine aggregates, coarse aggregate, water and

superplasticizers.

3.2.1 Cement

53 grade Ordinary Portland cement was used for this study program, as this cement

[31] is widely used in this country.. The physical and chemical requirement of 53

grade Ordinary Portland Cement as per IS 12269: 1987, is given in Table 3.1.

20

Since, different brands of cement have different strength development characteristics

and rheological behaviour in the compound compositions and fineness permitted in

IS: 12269, therefore cement from single supplier of same brand was used.

Table 3.1:Physical and chemical requirements of 53 grade OPC cement

Sl.no Test Conducted Results Requirements as per

IS:12269-1987(Ra1999)

1. Brand of cement Mahagold -

2. Type of cement 53 GradeOPC -

3. Normal Consistency 28.0% Not specified

4. Intial setting time 140 Minutes Shall not be less than

30 minutes

5. Final setting Time 225 Minutes Shall not be more than

600 minutes

6. Compressive strength:

(avg of three results)

3 days 44.6 Mpa Shall not be less than

27.0 Mpa

7 days 55.0 Mpa Shall not be less than

37.0 Mpa

28 days Awaited Shall not be less than

53.0 Mpa

7. FINENESS(by Blains

air permeability method)

326.0 m2/kg Shall not be less than

225.0 m2/kg

8. SOUNDNESS(by Le-

Chateliers method)

1.0 mm Shall not be more than

10 mm

9. Ratio of % of alumina to

that of iron oxide

1.22 Not less than 0.66

10. Insoluble Residue(%) 0.51 Not more than 3%

11. Magnesia(%) 1.11 Not more than 6%

12. Total loss on Ignition( %) 1.60 Not more than 4%

21

3.2.2 Fly Ash

The work done [33] on VTPS-fly ash has shown low reactivity and very less lime

content. The Vijayawada thermal Power station at Vijayawada has facilities of

collecting fly ash from hoppers in dry state with the help of electrostatic precipitator.

Fly ash collected from Vijayawada Thermal Power Plant at Vijayawada was a Class F

fly ash. It may also be noted that until very recent time, there has not been much

efforts in India to classify the dry-collected fly ash or to process the bulk collected dry

fly ash through separation of cenoshere, removal of carbon or further size reduction.

Fly ash was collected directly from hoppers in dry state with the help of electrostatic

precipitator are being used. From the previous study done on the same source of fly

ash [8,48], the following observations can be made.

Fly ash fulfil the criteria for lime reactivity specified in IS 3812-1981.

It was found that fly ash particles retained on 45 m sieve was very small (1.0-

1.5 percent) and 90 percent of particles have diameter between 17 and 20 m.

3.2.3 Sand

Natural River Sand was used which is locally available in Hyderabad region. The

specific gravity was found 2.57. Fineness Modulus is also determined using 10mm to

150 m and is found 2.972 as shown in Table 3.3. The fineness modulus gives the

idea about average size of particles in the fine aggregates. The value 2.972 indicates

medium size sand. The details of sieve analysis are presented in Table 3.2, and the

grading curve is shown in Figure 3.1. With sieve analysis data and fineness modulus

value, sand is considered as zone II grading sand of IS: 383 1970, which is

considered as good fine aggregate for concrete production. The grading limits of zone

II sand for fine aggregates as per IS: 383-1970 is also presented in Table 3.5.1, Table

3.5.2 for reference only.

22

GRADING OF FINE AND COURSE AGGREGATE

Table3.2: Sieve Analysis of Fine Aggregate

Weight Of sample: 2000gm

Fineness modulus = Cumulative %weight retained/100 =2972/100 =2.972

Grading Zone 11

Table: 3.3.1 Sieve Analysis of Coarse Aggregate (20mm) Weight of sample =5000gm

Fineness Modulus of Coarse Aggregate = 8.01

Sieve

Size

mm

Weight

Retained(gm)

% Weight

Retained

Cumulative %

Weight Retained

% Passing

40 0 0 0 100

20 0 0 0 100

10 0 0 0 100

4.75 36 1.80 1.80 98.20

2.36 150 7.50 9.30 90.70

1.18 560 28.0 37.30 62.70

600 476 23.80 61.10 38.90

300 554 27.70 88.80 11.20

150 202 10.10 98.90 1.10

L.P 22 1.10 100 0

Sieve

Size

mm

Weight

Retained(gm)

%

Weight

Retained

Cumulative %

Weight Retained

% Passing

40 0 0 0 100

20 310 6.20 6.20 93.80

12.5 4500 90.0 96.20 3.80

10 150 3.0 99.20 0.80

4.75 150 0.80 100 0

2.36 - - 100 0

1.18 - - 100 0

600 - - 100 0

300 - - 100 0

150 - - 100 0

23

Table 3.3.2: Sieve Analysis of Coarse Aggregate (12.5mm)

Weight of sample =5000gm

Sieve

Size

mm

Weight

Retained(gm)

% Weight

Retained

Cumulative %

Weight Retained

% Passing

20 0 0 0 100

12.5 50 1.0 1.0 99.0

10 1125 22.50 23.50 76.50

4.75 - - 100 0

2.36 - - 100 0

1.18 - - 100 0

600 - - 100 0

300 - - 100 0

150 - - 100 0

Fineness Modulus of Coarse Aggregate =6.245

Table 3.4: Combined Sieve Analysis Of 20mm And 12.5mmCoarse Aggregate

Table 3.5.1: Grading limits for Coarse Aggregates

IS Sieve

Designation

Percentage Passing for Single

Sized aggregate nominal size

(by weight)

Percentage Passing for graded

Aggregate of nominal size

(by weight)

20mm 12.5mm 10mm 20mm 12.5mm

20 85-

100

- - 95-100 100

12.5 - 85-100 100 - 90-100

10 0-20 0-45 85-100 25-55 40-85

4.75 0-5 0-10 0-20 0-10 0-10

2.36 - - 0-5 - -

Cumulative

Sieve size

(mm)

Cumulative

% Passing

20mm

Cumulative

% Passing

12.5mm

Cumulative %

Passing

When 20mm and

12.5mm are mixed

in 60:40 ratio

Requirements Of

Cumulative %

Passing for 20mm

graded aggregates

as per IS:383-

1970(RA2002)

40 100 100 100 100

20 93.80 100 96.30 95-100

12.5 3.80 99.0 41.90 --

10 0.80 76.50 31.30 25-55

4.75 0 0 0 0-10

24

Table 3.5.2: Grading limits of Fine Aggregates IS: 383-1970

IS Sieve

Designation

Percentage Passing by Weight for

Grading-1 Grading-11 Grading-111 Grading-1V

10mm 100 100 100 100

4.75mm 90-100 90-100 90-100 95-100

2.36mm 60-95 75-100 85-100 95-100

1.18mm 30-70 55-90 75-100 90-100

600 micron 15-34 35-59 60-79 80-100

300 micron 5-20 8-30 12-40 15-50

150 micron 0-10 0-10 0-10 0-15

3.2.4 Coarse Aggregate

Crushed 20mm maximum size was used. The specific gravity was found 2.65

.The sieve analysis is presented in table 3.3.1,3.3.2. And the grading curve is shown in

figure 3.2 . This confirming to the grading requirement as per IS: 383-1970, Which is

suitable for good quality concrete [34] the fineness modulus is also determined and it

is found to be 6.48,Details are presented in Table 3.3

1.1

11.2

38.9

62.7

90.798.2

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5

IS Sieve Size (mm)

Perc

en

tag

e P

assin

g

Figure 3.1: Grading curve for fine aggregate

25

Grading curve for coarse aggregate

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25

IS Sive Size (mm)

Pe

rce

nta

ge

pa

ss

ing

20

12.5

Graded

Figure 3.2: Grading curve for coarse aggregate

3.2.5 WATER

Ordinary tap water was used in the production of concrete.

3.2.6 SUPERPLASTISIZER

A High Range Water Reducing used was CONPLAST SP430 of FOSROC

CHEMICAL PVT. LTD. This super plasticiser is in dark brown colour, in an aqueous

solution. This is commercially available super plasticizer.

3.3 MIXTURE PROPORTIONING PROCEDURE

The basic steps involved in the Indian Standard method of concrete mix design can be

summarized as follows:

Step 1: Determination of Target Mean Strength or field strength

Target Mean Strength is determined as follows:

ft =fck + k s

Where ft = target mean compressive strength at 28 days,

fck = characteristics compressive strength at 28 days,

26

k = a statical value depending upon the accepted portions of low results and

the number of tests,

s = assumed standard deviation,

Note: As per IS: 456-2000, the value of k is taken 1.65, assuming that characteristic

strength is expected to fall not more than 5 percent of test result. And value of s is

also taken from IS 456-2000 table 8, which is given for each grade of concrete. The

value of s for M20 and M25 is 4 MPa and 5 MPa for M30 and M35 grade of concrete.

Step2: Selection of water-cement ratio:

The water-cement ratio is chosen from table no. IS: 456-2000[36], which specify the

minimum cement content, maximum water cement ratio and minimum grade of

concrete for the different exposure conditions with Normal Weight Aggregates of 200

mm Nominal Maximum Size. The value selected is compared with available relations

in SP: 23-1982[35], for the determination of water-cement ratio for the target mean

compressive strength at 28 days.

It is noted here that water-cement ratio for the determined target mean compressive

strength at 28 days gives lower value than specified maximum value in table 5 of IS:

456-2000. Even curve-E, which is applicable for 53 grade of OPC, in figure 47 of SP:

23-1982[35], which consider 28 days compressive strength of cement, incorporated in

the mix proportions, also gives slightly lesser value of water-cement ratio.

Step 3: Estimation of mixing water

The approximate water content is selected from the table 35 and 38 of SP: 23-1982[],

applicable for normal concrete mix, which considers the aggregate type (whether

crushed or uncrushed), maximum size of the aggregate and required slumps as a

measure of level of workability.

Step 4: Estimation of air content

The estimated entrapped air content is taken (2%) from table No. 41 of SP: 23-1982[],

based on nominal maximum size of the aggregate.

27

Step 5: Determination of cement content:

The cement content is calculated from the selected water-cement ratio and estimated

water content. The cement content so calculated is compared with the minimum

required cement content as per the durability consideration as stipulated in the IS:

456-2000[]. The greater of the two values is adopted. It is noted that the quantity

adopted is inclusive of the addition of part supplementary cementitious material to

OPC.

Step 6: Estimation of percentage of sand in total aggregates

The percentage of sand in total aggregates depends upon the grading of sand to be

incorporated in the mix. The general guideline is obtained from the figure 45 of SP:

23-1982[35], which is based on maximum size of coarse aggregates and the required

slump value targeted. It is to be noted that concrete with superplasticizers will have

different percentage of sand than concrete without super plasticizer for the same w/c

ratio.

Apart from the guidelines given in the figure 45 of the SP: 23-1982[35] for the

calculation of the percentage of sand in total aggregates, percentage of fine aggregates

is also seen in relation to the ratio of total fine contents (cement plus fly ash plus fine

aggregates) to total coarse aggregate content per m3

of mature. If it was not found in

the specified range then the percentage is adjusted accordingly. The ratio of total fines

to aggregates is a very important factor which influence the quality of concrete very

much, varies with the water-cement ratio of concrete for a given slump range values.

It is noted that that the water-cement ratio 0.46, 0.42 and 0.38 was kept for the

production of M20, M25,M30 and M35 concrete for slump range 80-120 mm in this

project work.

Step 7: Determination of fine and coarse aggregates

With the quantities of cement, fly ash, water and percentage of sand in total

aggregates already determined, the content of fine aggregates and coarse aggregates is

calculated from the following equations:

28

V = [W + C/Sc + F/Sp + (1 / p) * (fa / Sfa)] x 1/1000 -(2) for FA

V = [W + C/Sc + F/Sp + {1 /(1- p)} * (Ca / Sca)] x 1/1000 -(3) for CA.

Where V = absolute volume of fresh concrete i.e. gross volume (1 m3) minus the

volume of entrapped air,

W = mass of water (kg) per m3 of the concrete,

C = mass of cement (kg) per m3 of the concrete,

Sc = specific gravity of cement,

F = mass of fly ash (kg) per m3 of the concrete,

Sp = specific gravity of fly ash,(2.16)

P = ratio of fine aggregate to total aggregates by absolute volume

fa = total mass of fine aggregates (kg) per m3 of the concrete,

Sfa = specific gravity of saturated surface dry fine aggregates,

Ca = total mass of coarse aggregates (kg) per m3 of the concrete,

Sca = specific gravity of saturated surface dry coarse aggregates.

Step 8: Adjustment of the trial mixture proportions

The trial mixture proportions were adjusted according to the following guidelines to

achieve targeted slump (as a measure of workability).

(A) Moisture content as a part of quality control during production of

concrete. It is necessary to provide moisture content correction to dry

batching. In this project work sand and coarse aggregate are dried in room

temperature after sufficient amount of water sprinkled on the aggregate to

avoid further absorption of water from the estimated mixing water

quantity. The same quality control was maintained for each batch of

concrete produced.

(B) Initial slump- If initial slump is not achieved in the desired range, then the

mixing water is adjusted so as to maintain water cement ratio same. With

a change in mixing water quantity, sand quantity is also adjusted

accordingly.

29

Step 9: Selection of Optimum mixture proportions

Once trial mixes have adjusted, test specimens i.e. 150 mm cubes are cast from the

concrete produced and finally from the strength tests result of the specimens, optimum

of proportioning of mixture is suggested.

3.4 CALCULATION OF MIX PROPORTIONS:

The target strength of the concrete is fixed based on the standard deviation.

Considering good degree of quality control on ingredients, batching, mixing,

placement, curing and testing of concrete, Standard deviation is assumed 4 N/mm2

for

M20 and M25 and 5 N/mm2 for M30 and M35.

Thus, Target Mean Strength is determined from the following relation, which is

already stated.

ft = fck + k s

ft = 20 + 1.65 * 4 = 26.60 N/mm2 for M20

ft =25 + 1.65 * 4 = 31.60 N/mm2 for M25

ft =30 + 1.65 * 5 = 38.25 N/mm2 for M30

ft =35 + 1.65 * 5 =43.25N/mm2 - for M35

The water-cement ratio is selected for each grade of concrete as per table no. 5 of IS:

456-2000.

Absolute volume method as discussed in previous paragraph was used to determine

the quantities of different ingredients. Preliminary trials of mix were carried out to

exactly determine unit water content, fine aggregates percentages and slump (as a

measure of workability) of the concrete for each batch corresponding to the three

grades viz, M20, M25 and M30 and M35.

30

4 EXPERIMENT WORK

4.1 GENERAL

As discussed in previous chapters, the selection of materials, judicious mix

proportioning and proper workmanship (quality control) leads to high performance

concrete, which is required exhibit enhance strength and durability. In establishing

these requirements, careful consideration of properties of local available materials has

to be accounted for. Hence in this chapter main consideration is given to the planning,

material procurement, preparation of sample specimen, and finally testing them as per

IS code requirements.

4.2 PLANNING

In construction generally four mix (grades) are popular, which is M20, M25, M30 and

M35. So these four grades were chosen for experiments. Six variables of fly ash

replacement was taken which are control mix 0%, 15%, 20%, 25%, 30%, 35%

partially replacement of cement by fly ash. Study was carried out on both without

plasticiser and with-plasticiser Table 4.1 shows the nomenclature of different batches.

4.3 ESTIMATION OF REQUIRED MATERIAL:

Twenty four batches were to be made. Each batch would have 6 numbers of cubes.

According to above planning it was decided to cast 144 cubes. So after mix designing

quantity of material calculated taking account of 20% loses. Table 4.2 shows the

quantities of material required.

31

Table 4.1: Nomenclature of Different types of mix compositions

Cube

ID Cementetious Material

Grade of

concrete

W/(C +

F)

CM200 100 Percentage Cement M20 0.5

CF201 85 Percentage Cement + 15 Percentage Flyash M20 0.5























40

Table No:4.2 Mixture Proportions for M20, M25 Grades of concrete

Note : FA- Fine aggregates, CA Coarse aggregates, Spl. Super plasticizer (in Kg/m3)

Cementitious Material

Mix No:

W/(C + F)

Quantities in Kg/m3 Water

S.Pl

Cement Flyash FA CA

100 % Cement CM200 0.5 315.00 0.00 759 1152 157.5 2.20

85 % Cement + 15 % Flyash CF201 0.5 267.75 47.25 752 1141 157.5 2.00

80 % Cement + 20 % Flyash CF202 0.5 252.00 63.00 750 1139 157.5 1.63

75 % Cement + 25 % Flyash CF203 0.5 236.25 78.75 747 1135 157.5 1.63

70 % Cement + 30 % Flyash CF204 0.5 220.50 94.50 745 1131 157.5 1.63

65 % Cement + 35 % Flyash CF205 0.5 204.75 110.25 742 1127 157.5 1.63

100 % Cement CM250 0.46 340.00 0.00 750 1139 156.4 2.30

85 % Cement + 15 % Flyash CF251 0.46 289.00 51.00 742 1127 156.4 2.20

80 % Cement + 20 % Flyash CF252 0.46 272.00 68.00 739 1123 156.4 2.20

75 % Cement + 25 % Flyash CF253 0.46 255.00 85.00 736 1118 156.4 2.20

70 % Cement + 30 % Flyash CF254 0.46 238.00 102.00 734 1114 156.4 2.20

65 % Cement + 35 % Flyash CF255 0.46 221.00 119.00 732 1111 156.4 2.10

41

Table No: 4.3 Mixture Proportions for M20, M25 Grades of concrete

Cementitious Material Mix No: W/(C + F) Quantities in Kg/m

3

Water S.Pl

Cement Flyash FA CA

100 % Cement CM300 0.42 370.00 0.00 740 1124 155.4 2.88

85 % Cement + 15 % Flyash CF301 0.42 314.50 55.50 731 1110 155.4 2.64

80 % Cement + 20 % Flyash CF302 0.42 296.00 74.00 729 1106 155.4 2.64

75 % Cement + 25 % Flyash CF303 0.42 277.50 92.50 726 1102 155.4 2.64

70 % Cement + 30 % Flyash CF304 0.42 259.00 111.00 723 1098 155.4 2.40

65 % Cement + 35 % Flyash CF305 0.42 240.50 129.50 720 1094 155.4 2.40

100 % Cement CM350 0.38 400.00 0.00 730 1109 152 3.24

85 % Cement + 15 % Flyash CF351 0.38 340.00 60.00 721 1095 152 3.24

80 % Cement + 20 % Flyash CF352 0.38 320.00 80.00 718 1090 152 2.88

75 % Cement + 25 % Flyash CF353 0.38 300.00 100.00 715 1086 152 2.88

70 % Cement + 30 % Flyash CF354 0.38 280.00 120.00 712 1081 152 2.64

65 % Cement + 35 % Flyash CF355 0.38 260.00 140.00 709 1076 152 2.64

Note: FA- Fine aggregates, CA Coarse aggregates, Spl. Super plasticizer (in Liter/m3)

42

4.4 PROCUREMENT OF MATERIAL

Fly ash was procured from VTPS. Ordinary Portland cement of grade 53 was used.

Locally available materials for fine and coarse aggregate ware used.

4.5 PRELIMINARY LABORATORY TESTS

The testing of physical properties such as sieve analysis, unit weight and fineness

modulus of fine and coarse aggregates were carried out in a standard manner. The

results are shown in Tables 3.3 as already mentioned, which were required in

designing mix of concrete.

4.6 PREPARATIONS AND CASTING OF TEST SPECIMEN

Water to binder (cement and fly ash) ratio was kept 0.50, 0.46, 0.42 & 0.38 for M20,

M25, M30 & M35 grade of concrete respectively.

Each grade of concrete having 0, 15, 20, 25, 30, 35 percentage part replacement of

Ordinary Portland cement to VTPS fly ash, with super plasticizers with same water

content for a given mix proportion.

4.7 MIXING PROCEDURE

The 20 mm coarse and fine aggregates were initially fed into the concrete mixer.

Cement, fly ash fed and then 10 mm size coarse aggregate fed. Superplasticizer is

well mixed in half water. Start the mixer for one minute to dry mix the aggregates and

binder, and then gradually half quantity of water is pored. While the mixer was in

operated condition, remaining water and superplasticizer mix added into the mixer.

The mixing time was 2.2 to 3.5 minutes (approximately) from the time when all the

mix ingredients had been charged into the mixer.

4.8 COMPACTION OF TEST SPECIMENS

Cubes were casted in three layers. For all specimens steel moulds were used.

43

4.9 SPECIMEN CONDITIONING AND TESTING

After casting, the specimens were stored for 24 h in the laboratory environment

(27 5 ) and then demoulded and stored in curing tank at room temperature till the

time of testing.

The compressive strength of the cubes was determined after 7 and 28 days of casting.

Table 4.4: Properties of hardened concrete (M20, M25 grades):-

Cementitious Material Mix No: W/(C + F) Compressive Strength

7- days 28- days

100 % Cement CM200 0.5 28.83 37.34

85 % Cement + 15 % Flyash CF201 0.5 25.84 36.90

80 % Cement + 20 % Flyash CF202 0.5 23.31 35.07

75 % Cement + 25 % Flyash CF203 0.5 20.27 33.25

70 % Cement + 30 % Flyash CF204 0.5 19.53 32.18

65 % Cement + 35 % Flyash CF205 0.5 17.83 29.05

100 % Cement CM250 0.46 28.12 51.58

85 % Cement + 15 % Flyash CF251 0.46 26.34 50.27

80 % Cement + 20 % Flyash CF252 0.46 25.38 47.01

75 % Cement + 25 % Flyash CF253 0.46 23.81 46.42

70 % Cement + 30 % Flyash CF254 0.46 21.74 43.59

65 % Cement + 35 % Flyash CF255 0.46 21.38 38.44

Note: 1. Test for compressive strength was carried out on 150x150x150mm cubes

2. Each value is average of three test results

44

Table 4.5: Properties of hardened concrete (M30, M35 grades):-

Cementitious Material Mix No: W/(C + F) Compressive Strength

7- days 28- days

100 % Cement CM300 0.42 30.22 54.67

85 % Cement + 15 % Flyash CF301 0.42 27.7 52.61

80 % Cement + 20 % Flyash CF302 0.42 26.36 51.62

75 % Cement + 25 % Flyash CF303 0.42 25.69 47.31

70 % Cement + 30 % Flyash CF304 0.42 24.99 45.00

65 % Cement + 35 % Flyash CF305 0.42 24.32 42.86

100 % Cement CM350 0.38 36.93 57.83

85 % Cement + 15 % Flyash CF351 0.38 35.77 54.82

80 % Cement + 20 % Flyash CF352 0.38 34.06 53.40

75 % Cement + 25 % Flyash CF353 0.38 33.4 50.41

70 % Cement + 30 % Flyash CF354 0.38 29.92 48.76

65 % Cement + 35 % Flyash CF355 0.38 27.61 46.42

Note: 1. Test for compressive strength was carried out on 150x150x150mm cubes

2. Each value is average of three test results

45

TEST RESULTS AND DISCUSSION

5.1 GENERAL

The results of all the tests carried out on VTPS fly ash mix concrete and control

concrete are presented and discussed in this chapter.

5.2 TEST RESULTS

First of all some basic tests like sieve analysis of fine and coarse aggregate were

conducted then fineness modulus is find out and compared with the table given in IS

code. For the graded mix coarse aggregate requirement 40%, 10 mm size aggregate

and 60%, 20 mm aggregate used. After this control concrete mix of M20, M25, M30 and

M35 were designed as per IS code provisions. The details of the mix designs are listed

in Table 4.2.

Twenty four samples of 6 cubes 150x150x150 size each (total 144 cubes) casted for

0%, 15%, 20%, 25%, 30%, 35% partially replacement of cement by fly ash with super

plasticizer and tested at 7th

and 28 days. The detail results of compression tests are

summarized in Table 4.4 and 4.5

5.2.1 PROPERTIES OF FRESH CONCRETE

Specific Gravity:

The specific gravity of VTPS fly ash was determined to be 2.16, which is much lower

than the specific gravity of cement (3.15). So partially replacement of cement by fly

ash reduces the density of concrete. Results are shown in Fig. 5.1

46

Density variation with increase of Flyash

2330

2340

2350

2360

2370

2380

2390

2400

0 10 20 30 40

Percentage Flyash

De

ns

ity

Kg

/cu

m

M20

M25

Fig: 5.1.1 Density Vs Flyash Graph

Fig: 5.1.2 Density Vs Flyash Graph

47

Slump and Vee Bee Time

The replacement of cement (by mass) with five percentage of fly ash (0%, 15%, 20%,

25%, 30%, 35%) increased the workability. For the economical consideration the SPL

dosage will be reduced due to increment of Flyash Percentage to maintain the slump

between 80 120 mm. This is due to the ball Bearing action of the spherical

particles of fly ash. Results are shown in Fig. 5.2. (a), 5.2 (b), 5.2 (c), 5.2 (d)

Fig. 5.2(a): Fly ash Vs Slump Graph

S l ump Gr a ph f or M 2 5 Gr a de c onc r e t e

80

90

100

110

120

130

0 5 10 15 20 25 30 35 40

Percentage Flyash

Slu

mp

(m

m)

with SP

Fig.5.2 (b): Fly ash Vs Slump Graph

48

Slump Graph for M30 Grade concrete

70

80

90

100

110

120

130

0 5 10 15 20 25 30 35 40

Persentage Flyash

Slu

mp

(m

m)

w ith SP

Fig.5.2(c): Fly ash Vs Slump Graph

Slump Graph for M35 Grade concrete

70

80

90

100

110

120

130

0 5 10 15 20 25 30 35 40

Percentage Flyash

Slu

mp

(m

m)

w ith SP

Fig.5.2(c): Fly ash Vs Slump Graph

49

5.2.2 PROPERTIES OF HARDENED CONCRETE:

7 Days compressive strength

The replacement of cement (by mass) with five percentage of fly ash (15%, 20%,

25%, 30%, 35%) content reduced the compressive strength of concrete (for M35

Grade) 3.14%,7.77%,9.55%,18.98%,25.23%respectively. This is probably due to

non-contribution in compressive strength of fly ash at early age. Results are shown in

Fig. 5.3.

28 days compressive strength

The replacement of cement (by mass) with five percentage of fly ash

(15%,20%,25%,30%,35%) content improves the strength gain but still reduced(for

M35 Grade) by 5.2%,7.66%,12.83%,15.68%, and 19.73% respectively with super

plasticizer. Fly ash starts reaction with Ca(OH)2 after 14 days. Results are listed in

Fig. 5.3 (a).

Compressive Strength of M20 Grade Concrete

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25 30 35 40

Percentage of Flyash

Str

ength

in M

Pa

7 Days Strength

28 Days Strength

Fig. 5.3 (a): Variation in Compressive Strength with Fly ash Increase

50


15

20

25

30

35

40

45

50

55

0 5 10 15 20 25 30 35 40


Str

ength

in M

Pa

7 Days Strength

28 Days Strength

Fig. 5.3 (b): Variation in Compressive Strength with Fly ash Increase


20

25

30

35

40

45

50

55

60

0 5 10 15 20 25 30 35 40


Str

en

gth

in

Mp

a

7 Days Strength

28 Days Strength

Fig. 5.3(c): Variation in Compressive Strength with Fly ash Increase

51


20

25

30

35

40

45

50

55

60

0 5 10 15 20 25 30 35 40

Percentage of flyash

Str

ength

in M

Pa

7 Days Strength

28 Days Strength

Fig. 5.3(d): Variation in Compressive Strength with Fly ash Increase

52

56 days compressive strength (Imaginary graphical representation)

The replacement of cement (by mass) with five percentage of fly ash

(15%,20%,25%,30%,35%) content of (ex:for M35 grade) concrete given strength

almost equal to control mix. This shows that fly ash reaction continues for longer time

up to 90 days or more. Results are listed in Fig. 5.3 (e).


20

30

40

50

60

70

0 5 10 15 20 25 30 35 40


Str

ength

MP

a:

7 Days Strength

28 Days Strength

56 Days Strength

Fig. 5.3(e): Variation in Compressive Strength with Fly ash Increase

53

4.2.6.1.1.1 CONCLUSIONS

In this chapter conclusions of the so far done study/Experimental work of this project

are given. Following conclusions are given from the present study:

VTPS Fly ash (class F) incorporation in the mix ingredient enhances

performance of concrete by improving workability, flow-ability, finishibility

and compactibility in fresh state of concrete in both plasticizerised as well as

unplasticizeried concrete.

Increasing fly ash content decreases the strength. Although the strength of

High Fly ash Concrete (HFC) is very poor at early curing age, it develops

rapidly with longer curing age, resulting in long-term strength almost equal to

that of control mix (with no fly ash).

By the analysis fly ash effect in HFC becomes positive after 7 days of curing

age, and it develops rapidly. The contribution of fly ash in HFC with 56-day

curing age to strength is equal or approaches 80%, and is more remarkable

compressive strength.

Finally, cement contribution to strength of HFC can be divided into two

aspects. The first is through the hydrated products produced in the hydration

of itself, and the second is the fly ash effect activated by it. At early curing

age, the former is the dominant factor, while the latter is more significant

afterward. After 56 days, the contribution of fly ash effect to strength of HFC

approaches 80%.

Incorporating fly ash by high content and super-substituting method makes

HFC easier to compact, and together with the amount of crystal phase

Ca(OH)2 and harmful pore reduction, HFC at long-term curing age becomes

dense and homogeneous.

With the current data and results, it is very possible to design a mix with

VTPS fly ash as supplementary material in concrete that will be more durable

and economical.

54

5

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