investigation on fly ash as a partial cement replacement in concrete

A PROJECT REPORT ON

INVESTIGATION ON FLY ASH AS A PARTIAL CEMENT REPLACEMENT IN CONCRETE

SUBMITTED IN PARTIAL FULFILLMENT OF THE

REQUIREMENT FOR THE AWARD OF THE DEGREE

3

DEPARTMENT OF CIVIL ENGINEERING

BASANTIKA INSTITUTE OF ENGINEERING AND TECHNOLOGY

A PROJECT REPORT ON


SUBMITTED IN PARTIAL FULFILLMENT OF THE

REQUIREMENT FOR THE AWARD OF THE DEGREE

OF

DIPLOMA

IN

CIVIL ENGINEERING

BY

3RD

YEAR STUDENTS; B.I.E.T (P),2014

UNDER THE GUIDANCE OF

Mr. SUBHAJIT ROY

(LECTURER)

DEPARTMENT OF CIVIL ENGINEERING

BASANTIKA INSTITUTE OF ENGINEERING AND TECHNOLOGYGANPUR; MD.BAZAR

BIRBHUM-731216 MAY, 2014


BASANTIKA INSTITUTE OF ENGINEERING AND TECHNOLOGY (POLYTECHNIC)

TABLE OF CONTENTS

LIST OF FIGURES I LIST OF TABLES Ii CANDIDATE’S DECLARATION Iii CERTIFICATE Iv ACKNOLEDGEMENT V ABSTRACT Vi CHAPTER 1: INTRODUCTION 1

1.1. AIMS OF THE PROJECT 1 1.2. ASH PRODUCTION AND ITS AVAILABILITY 1 1.3. VARIOUS USAGE OF ASH 3 1.4. CENOSPHERES 3 1.5. CEMENT CONCRETE 4

CHAPTER 2: LITERATURE REVIEW 5 2.1. CONCRETE AND ENVIRONMENT 5 2.2. FLY ASH 6

CHAPTER 3: FLY ASH WORKS WITH CEMENT 7 3.1. FLY ASH HELPS IN CONCRETE 7

3.1.1. REDUCED HEAT OF HYDRATION 8 3.1.2. WORKABILITY OF CONCRETE 9 3.1.3. PERMEABILITY AND CORROSION PROTECTION 9

3.2. HOW FLY ASH CAN BE USED IN CEMENT CONCRETE? 9 3.2.1. SIMPLE REPLACEMENT METHOD 10 3.2.2. ADDITION METHOD 10 3.2.3. MODIFIED REPLACEMENT METHOD 10

CHAPTER 4: EFFECTS 11 4.1. EFFECT OF FLY ASH ON CARBONATION OF CONCRETE 11 4.2. SULPHATE ATTACK 11 4.3. CORROSION OF STEEL 11 4.4. REDUCED ALKALI- AGGREGATE REACTION 11 4.5. ENVIRONMENTAL BENEFITS OF FLY ASH USE IN CONCRETE 12 4.6. PHYSICAL PROPERTIES 12 4.7. POZZOLANIC PROPERTIES OF FLY ASH 12 4.8. POZZOLANIC ACTIVITY 12

CHAPTER 5: QUALITY 13 5.1. BUREAU OF INDIAN STANDARD 13 5.2. ASTM INTERNATIONAL FOR FLY ASH 14

CHAPTER 6: MIX DESIGN 16 6.1. CRITERIA FOR MIX DESIGN 16 6.2. ILLUSTRATIVE EXAMPLE OF CONCRETE MIX DESIGN

(GRADE M 20) 16

6.2.1. DESIGN STIPULATIONS 16 6.2.2. TEST DATA FOR MATERIAL 16 6.2.3. SIEVE ANALYSIS OF COARSE AGGREGATE 17 6.2.4. SIEVE ANALYSIS OF FINE AGGREGATE 17

6.2.5. TARGET MEAN STRENGTH OF CONCRETE 18 6.2.6. SELECTION OF WATER-CEMENT RATIO 18 6.2.7. SELECTION OF WATER AND SAND CONTENT 19 6.2.8. DETERMINATION OF CEMENT CONTENT 20 6.2.9. DETERMINATION OF COARSE AND FINE AGGREGATE

CONTENTS 20

CHAPTER 7: THE COMPRESSIVE STRENGTH OF CUBIC CONCRETE SPECIMENS BS 1881: PART 116: 1983

22

7.1. SCOPE 22 7.2. APPARATUS 22 7.3. PROCEDURE 22 7.4. TYPE OF FAILURE 22 7.5. CALCULATIONS 23

CHAPTER 8: TABULATION FORM OF TESTED RESULTS 25 8.1. NORMAL CEMENT CONCRETE (M15) 25 8.2. 5% FLY ASH MIXED CEMENT CONCRETE (M15) 26 8.3. 10% FLY ASH MIXED CEMENT CONCRETE (M15) 27 8.4. 20% FLY ASH MIXED CEMENT CONCRETE (M15) 28 8.5. NORMAL CEMENT CONCRETE (M20) 29 8.6. 5% FLY ASH MIXED CEMENT CONCRETE (M20) 30 8.7. 10% FLY ASH MIXED CEMENT CONCRETE (M20) 31 8.8. 20% FLY ASH MIXED CEMENT CONCRETE (M20) 32 8.9. NORMAL CEMENT CONCRETE (M25) 33 8.10. 5% FLY ASH MIXED CEMENT CONCRETE (M25) 34 8.11. 10% FLY ASH MIXED CEMENT CONCRETE (M25) 35 8.12. 20% FLY ASH MIXED CEMENT CONCRETE (M25) 36

CHAPTER 9: CONCLUSIONS 37 9.1. RECOMMENDATIONS FOR FUTURE RESEARCH 38

REFERENCES 39

[i]

LIST OF FIGURES

FIGURE NO.

FIGURE NAME PAGE NO.

1.1 Ash Pond. 02 1.2 Fly Ash after Oven Drying. 03 3.1 Microscopic Photographs of Fly Ash and Cement Particles. 08 7.1 Satisfactory Failures. 23 7.2 Unsatisfactory Failures. 23 7.3 The Compression Testing Machine. 24 8.1 Relation between Crushing Strength of Concrete and Days of

Curing of Normal Cement Concrete (M15). 25

8.2 Relation between Crushing Strength of Concrete and Days of Curing of 5% Fly Ash mixed Cement Concrete (M15).

26


27


28

8.5 Relation between Crushing Strength of Concrete and Days of Curing of Normal Cement Concrete (M20).

29


30


31


32

8.9 Relation between Crushing Strength of Concrete and Days of Curing of Normal Cement Concrete (M25).

33


34


35


36

8.13 Comparison between normal cement concrete and fly ash mixed cement concrete (M15).

37


38


39

[ii]

LIST OF TABLES

TABLE NO.

TABLE NAME PAGE NO.

4.1 Salient Advantage of using Fly Ash in Cement Concrete. 12 5.1 Chemical Requirements of Fly Ash according to Bureau of Indian

Standard (BIS). 13

5.2 Physical Requirements of Fly Ash according to Bureau of Indian Standard (BIS).

14

5.3 Chemical Requirements of Fly Ash according to ASTM International.

14

5.4 Physical Requirements of Fly Ash according to ASTM International.

15

6.1 Values of Tolerance Factor (t) (Risk Factor). 17 6.2 Assumed Standard Deviation as per IS 456:2000. 18

6.3

Minimum Cement Concrete Maximum W/C Ratio and Minimum Grade of Concrete for Different Exposures with Normal weight Aggregates of 20mm Nominal Maximum Size IS 456:2000.

18

6.4 Approximate Sand and Water contents per cubic metre of concrete W/C=0.60 Workability=0.80 C.F.

19

6.5 Adjustment values in water content and sand percentage for other conditions.

19

6.6 Approximate Entrapped Air Content. 20 8.1 Tested Result of Normal Cement Concrete (M15). 25 8.2 Tested Result of 5% Fly Ash Mixed Cement Concrete (M15). 26 8.3 Tested Result of 10% Fly Ash Mixed Cement Concrete (M15). 27 8.4 Tested Result of 20% Fly Ash Mixed Cement Concrete (M15). 28 8.5 Tested Result of Normal Cement Concrete (M20). 29 8.6 Tested Result of 5% Fly Ash Mixed Cement Concrete (M20). 30 8.7 Tested Result of 10% Fly Ash Mixed Cement Concrete (M20). 31 8.8 Tested Result of 20% Fly Ash Mixed Cement Concrete (M20). 32 8.9 Tested Result of Normal Cement Concrete (M25). 33

8.10 Tested Result of 5% Fly Ash Mixed Cement Concrete (M25). 34 8.11 Tested Result of 10% Fly Ash Mixed Cement Concrete (M25). 35 8.12 Tested Result of 20% Fly Ash Mixed Cement Concrete (M25). 36

[iii]

CANDIDATE’S DECLARATION

We hereby declare that the work which is being presented in this project

entitled “INVESTIGATION ON FLY ASH AS A PARTIAL CEMENT REPLACEMENT IN CONCRETE” in partial fulfillment of the requirements for the award of the degree of Diploma in Civil Engineering, Basantika Institute Of Engineering And Technology (Polytechnic), is an authentic record of our own work carried out under the supervision of Mr. Subhajit Roy, Lecturer , Department of Civil Engineering, Basantika Institute Of Engineering And Technology (Polytechnic) Ganpur, Md.Bazar, Birbhum.

The matter embodied in this project has not been submitted for the award of any other degree or diploma.

Sk.Md. Nayar

CE-39

Soumen De

CE-44

Debabrata Shaw

CE-33

Bishwajit Kundu

CE-37

Md Nurjamal Ali

CE-43

Taniya Sarkar

CE-41

Mukesh kr. Roy

CE-11

Jannat-ul-Ferdows

CE-01

Susuma Garian

CE-21

Supriyo Mandal

CE-65

Md.Islam Sk

CE-63

Md.Najmi Alam

CE-64

Nazrul Islam

CE-73

Asiqur Rahaman

CE-77

Surojit Mukherjee

CE-22

Surojit Das

CE-48

A.M Amirul Akhtar

CE-50

Subrata Pal

CE-42

[iv]

CERTIFICATE

This is to certify that the project entitled “INVESTIGATION ON FLY ASH AS A PARTIAL CEMENT REPLACEMENT IN CONCRETE” in partial fulfillment of the requirements for the award of the degree of Diploma in Civil Engineering, Basantika Institute Of Engineering And Technology (Polytechnic), is bonafied representation of the work carried out by 3rd year Civil Engineering students under the guidance of Mr. Subhajit Roy , Lecturer , Department of Civil Engineering, Basantika Institute Of Engineering And Technology (Polytechnic) Ganpur, Md.Bazar, Birbhum.

[v]

ACKNOLEDGEMENT We wish to express our sincere regards and gratitude to Mr. Subhajit Roy

and Mr. Suman Kumar Dhali Lecturer of Civil Engineering for his encouragement of this project.

We are thankful to Mr. Prabuddha Shyamal ,H.O.D, Department of Civil

Engineering and Mr. Keshab Chandra Barai, Lecturer, Department of Civil Engineering for their guidance and encouragement whole hearted co-operation and suggestion in preparation of this project. We are also thankful to Mr. Anupam Barai, Mr. Atikur Rahaman, Mr. Sabyasachi Dutta, Mr. Indranil Choudhury and Mr.Yeanafiul Islam Biswas, Lecturer, Department of Civil Engineering for his guidance in performing all the related experiment for this project work.

We have no adequate works to express our deep sense of gratitude to our

parents and family members who have a constant source of inspiration.

Sk.Md. Nayar

CE-39

Soumen De

CE-44

Debabrata Shaw

CE-33

Bishwajit Kundu

CE-37

Md Nurjamal Ali

CE-43

Taniya Sarkar

CE-41

Mukesh kr. Roy

CE-11

Jannat-ul-Ferdows

CE-01

Susuma Garian

CE-21

Supriyo Mandal

CE-65

Md.Islam Sk

CE-63

Md.Najmi Alam

CE-64

Nazrul Islam

CE-73

Asiqur Rahaman

CE-77

Surojit Mukherjee

CE-22

Surojit Das

CE-48

A.M Amirul Akhtar

CE-50

Subrata Pal

CE-42

[vi]

ABSTRACT

The use of Portland cement in concrete construction is under critical review due to high amount of carbon dioxide gas released to the atmosphere during the production of cement. In recent years, attempts to increase the utilization of fly ash to partially replace the use of Portland cement in concrete are gathering momentum. Most of this by-product material is currently dumped in landfills, creating a threat to the environment.

Fly ash based concrete is a ‘new’ material that does not need the presence of Portland cement as a binder. Instead, the source of materials such as fly ash, that are rich in Silicon (Si) and Aluminium (Al), are activated by alkaline liquids to produce the binder.

This project reports the details of development of the process of making fly ash-based concrete. Due to the lack of knowledge and know-how of making of fly ash based concrete in the published literature, this study adopted a rigorous trial and error process to develop the technology of making, and to identify the salient parameters affecting the properties of fresh and hardened concrete. As far as possible, the technology that is currently in use to manufacture and testing of ordinary Portland cement concrete were used.

Fly ash was chosen as the basic material to be activated by the geopolimerization process to be the concrete binder, to totally replace the use of Portland cement. The binder is the only difference to the ordinary Portland cement concrete. To activate the Silicon and Aluminium content in fly ash, a combination of sodium hydroxide solution and sodium silicate solution was used.

Manufacturing process comprising material preparation, mixing, placing, compaction and curing is reported in the thesis. Napthalene-based superplasticiser was found to be useful to improve the workability of fresh fly ash-based concrete, as well as the addition of extra water. The main parameters affecting the compressive strength of hardened fly ash-based concrete are the curing temperature and curing time, The molar H2O-to-Na2O ratio, and mixing time.

Fresh fly ash-based concrete has been able to remain workable up to at least 120 minutes without any sign of setting and without any degradation in the compressive strength. Providing a rest period for fresh concrete after casting before the start of curing up to five days increased the compressive strength of hardened concrete.

The elastic properties of hardened fly ash-based concrete, i,e. the modulus of elasticity, the Poisson’s ratio, and the indirect tensile strength, are similar to those of ordinary Portland cement concrete. The stress-strain relations of fly ash-based concrete fit well with the expression developed for ordinary Portland cement concrete.

[1]

CHAPTER 1

INTRODUCTION

After wood, concrete is the most often used material by the community. Concrete is conventionally produced by using the ordinary Portland cement (OPC) as the Primary binding Material. The environmental issues associated with the production of OPC are well known. The amount of the carbon dioxide released during the manufacture of OPC due to the calcinations of limestone and combustion of fossil fuel is in the order of one ton for every ton of OPC produced. In addition, the amount of energy required to produce OPC is only next to steel and aluminum.

On the other side, Electricity is the key for development of any country. Coal is a major source of fuel for production of electricity in many countries in the world. In the process of electricity generation large quantity of fly ash get produced and becomes available as a byproduct of coal-based power stations. It is a fine powder resulting from the combustion of powdered coal - transported by the flue gases of the boiler and collected in the Electrostatic Precipitators (ESP).

Conversion of waste into a resource material is an age-old practice of civilization .The fly ash became available in coal based thermal power station in the year 1930 in USA. For its gainful utilization, scientist started research activities and in the year 1937, R.E.Davis and his associates at university of California published research details on use of fly ash in cement concrete. This research had laid foundation for its specification, testing &usages.

1.1 AIMS OF THE PROJECT :- The present study deals with the manufacture of low calcium (ASTM Class F) fly ash-based concrete, the parameters influencing the mixture proportioning, and the short-term engineering properties in the fresh and hardened states. The research reported in this thesis is the first stage of a research project on fly ash-based concrete currently in progress in the Faculty of Engineering and Computing at Curtin University of Technology, Perth, Australia.

The aims of the project are:

I. To develop a mixture proportioning process of making fly ash-based concrete. II. To identify and study the effect of salient parameters that affects the properties of fly ash-based

concrete. III. To study the short-term engineering properties of fresh and hardened fly ash based concrete.

1.2 ASH PRODUCTION AND ITS AVAILABILITY :- Any country's economic & industrial growth depends on the availability of power. In India also, coal is a major source of fuel for power generation. About 60% power is produced using coal as fuel. Indian coal is having low calorific value (3000-3500 Kcal.) & very high ash content (30-45%) resulting in huge quantity of ash is generated in the coal based thermal power stations. During 2005-06 about 112 million tonne of ash has been generated in 125 such power stations. With the present growth in power sector, it is expected that ash generation will reach to 175 million tonne per annum by 2012.

[2]

FIG-1.1 ASH POND

Any coal based thermal power station may have the following four kinds of ash:

I. Fly Ash:-This kind of ash is extracted from flue gases through Electrostatic Precipitator in dry form. This ash is fine material & possesses good pozzolanic property.

II. Bottom Ash:- This kind of ash is collected in the bottom of boiler furnace. It is comparatively coarse material and contains higher unburnt carbon. It possesses zero or little pozzolanic property.

III. Pond Ash:-When fly ash and bottom ash or both mixed together in any proportion with the large quantity of water to make it in slurry form and deposited in ponds wherein water gets drained away. The deposited ash is called as pond ash.

IV. Mound Ash:-Fly ash and bottom ash or both mixed in any proportion and deposited in dry form in the shape of a mound is termed as mound ash.

As per the Bureau of Indian Standard IS: 3812 (Part-1) all these types of ash is termed as Pulverized Fuel Ash(PFA).

Fly ash produced in modern power stations of India is of good quality as it contains low sulphur & very low unburnt carbon i.e. less loss on ignition. In order to make fly ash available for various applications, most of the new thermal power stations have set up dry fly ash evacuation & storage system. In this system fly ash from Electrostatic Precipitators (ESP) is evacuated through pneumatic system and stored in silos. From silos, it can be loaded in open truck/closed tankers or can be bagged through suitable bagging machine.

[3]

In the ESP, there are 6 to 8 fields (rows) depending on the design of ESP. The field at the boiler end is called as first field & counted subsequently 2 , 3 onwards. The field at chimney end is called as last field. The coarse particles of fly ash are collected in first fields of ESP. The fineness of fly ash particles increases in subsequent fields of ESP.

1.3 VARIOUS USAGE OF ASH :- Pulverized Fuel Ash is versatile resource material and can be utilized in variety of application. The pozzolanic property of fly ash makes it a resource for making cement and other ash based products. The Geo-technical properties of bottom ash,pond ash & coarse fly ash allow it to use in construction of e m b a n k m e n t s , structural fills, reinforced fills low lying area development etc. The physico chemical properties of pond ash is similar to soil and it contains P, K, Ca, Mg, Cu, Zn, Mo, and Fe, etc. which are essential nutrients for plant growth. These properties enable it to be used as a soil amender & source of micronutrients in Agriculture/ Soil Amendment.

The major utilization areas of PFA are as under: -

I. Manufacture of Portland Pozzolana Cement & Performance improver in Ordinary Portland Cement (OPC).

II. Part replacement of OPC in cement concrete. III. High volume fly ash concrete. IV. Roller Compacted Concrete used for dam & pavement construction. V. Manufacture of ash bricks and other building products.

VI. Construction of road embankments, structural fills, low lying area development. VII. As a soil amender in agriculture and wasteland development.

1.4 CENOSPHERES :- Cenospheres are lightweight, inert, hollow spheres, filled with air / gases having light grey or off white in colour and comprises largely of silica and alumina. By virtue of hollowness inside, these spherical particles imparts properties like low thermal conductivity, high electrical insulation and good sound proof characteristics. The shell is of aluminium silicate material, which provides hardness, resistance to wear and chemical inertness to particles. Because of these excellent engineering properties, cenospheres are high value material and are used as mineral fillers in plastic, polymers, rubber, paints, refractory, automotive composites, aerospace coatings and composites, propeller blades, oil well cement etc.

[4]

1.5 CEMENT CONCRETE :- Cement concrete - most widely used construction material in the world over, commonly consists of cement, aggregates (fine and coarse) and water. It is the material, which is used more than any other man made material on the earth for construction works. In the concrete, cement chemically reacts with water and produces binding gel that binds other component together and creates stone type of material. The reaction process is called 'hydration' in which water is absorbed by the cement. In this process apart from the binding gel, some amount of lime [Ca (OH)2] is also liberated. The coarse and fine aggregates act as filler in the mass. The main factors which determine the strength of concrete is amount of cement used and the ratio of water to cement in the concrete mix. However, there are some factors which limits the quantity of cement and ratio of water / cement to be used in the concrete. Hydration process of cement is exothermic and large amount of heat is liberated. Higher will be the cement content greater will be the heat liberation leading in distress to concrete.

Water is the principal constituent of the concrete mix. Once the concrete is hardened, the entrapped water in the mass is used by cement mineralogy for hydration and some water is evaporated, thus leaving pores in the matrix. Some part of these pores is filled with hydrated products of cement paste. It has been observed that higher the ratio of water / cement, higher is the porosity resulting in increased permeability.

Use Of Portland Cement In Concrete Started About 180 Years Ago. The Concept Of High Strength Mean Higher Durability Developed With Low-Grade Cement Inculcated Confidence And Portland Cement Became Unique Construction Material Of The World.

After the World war II, the need of high-speed construction necessitated the development of high-grade cement providing early high strength. The high-grade cements have been developed by changing the ratio of mineralogical constituents of the cement particularly by increasing the ratio of Tricalcium Silicate (C3S) to Dicalcium Silicate (C2S) and increasing the fineness of the cement. Actually, these changes have resulted in high early strength rather than high strength cement. It has been found out that buildings constructed using high grade cement during 1940-50 have ceded premature distress within 10-20 years. When the detailed analysis was carried out, it was revealed that :

i. As the hydration of cement takes place progressively, lime is also liberated gradually. A small quantity of this liberated lime is used to maintain pH of the concrete and the major portion remains unused/ surplus and makes concrete porous.

ii. The high-grade cement which has high C S, releases higher amount of surplus lime resulting in higher porosity in the concrete mass.

iii. Further, higher heat of hydration, higher water content and high porosity increases the susceptibility of concrete mass when it is exposed to a range of external and internal aggressive environment. This disturbs the soundness of the concrete and result in reduced durability.

iv. To mitigate the above problem subsequent research work was carried out which established that use of fly ash or Pozzolana helps to solve all problems related to durability of concrete mass.

[5]

CHAPTER 2

LITERATURE REVIEW

This chapter presents a background to the needs on the development of a fly ash based technology. The available published literature on fly ash based concrete technology is also briefly reviewed.

2.1 CONCRETE AND ENVIRONMENT :- The trading of carbon dioxide (CO2) emissions is a critical factor for the industries, including the cement industries, as the greenhouse effect created by the emissions is considered to produce an increase in the global temperature that may result in climate changes. The ‘tradeable emissions’ refers to the economic mechanisms that are expected to help the countries worldwide to meet the emission reduction targets established by the 1997 Kyoto Protocol. Speculation has arisen that one ton of emissions can have a trading value about US$10 (Malhotra 1999; Malhotra 2004).

The climate change is attributed to not only the global warming, but also to the paradoxical global dimming due to the pollution in the atmosphere. Global dimming is associated with the reduction of the amount of sunlight reaching the earth due to pollution particles in the air blocking the sunlight. With the effort to reduce the air pollution that has been taken into implementation, the effect of global dimming may be reduced, however it will increase the effect of global warming (Fortune 2005). In this view, the global warming phenomenon should be considered more seriously, and any action to reduce the effect should be given more attention and effort.

The production of cement is increasing about 3% annually (McCaffrey 2002). The production of one ton of cement liberates about one ton of CO2 to the atmosphere, as the result of de carbonation of limestone in the kiln during manufacturing of cement and the combustion of fossil fuels (Roy 1999).

The contribution of Portland cement production worldwide to the greenhouse gas emission is estimated to be about 1.35 billion tons annually or about 7% of the total greenhouse gas emissions to the earth’s atmosphere (Malhotra 2002). Cement is also among the most energy-intensive construction materials, after aluminium and steel. Furthermore, it has been reported that the durability of ordinary Portland cement (OPC) concrete is under examination, as many concrete structures, especially those built in corrosive environments, start to deteriorate after 20 to 30 years, even though they have been designed for more than 50 years of service life (Mehta and Burrows 2001).

The concrete industry has recognized these issues. For example, the U.S. Concrete Industry has developed plans to address these issues in ‘Vision 2030: A Vision for the U.S. Concrete Industry’. The document states that ‘concrete technologists are faced with the challenge of leading future development in a way that protects environmental quality while projecting concrete as a construction material of choice. Public concern will be responsibly addressed regarding climate change resulting from the increased concentration of global warming gases.’ In this document, strategies to retain concrete as a construction material of choice for infrastructure development, and at the same time to make it an environmentally friendly material for the future have been outlined (Mehta 2001; Plenge 2001).

In order to produce environmentally friendly concrete, Mehta (2002) suggested the use of fewer natural resources, less energy, and minimise carbon dioxide emissions. He categorised these short-term efforts as ‘industrial ecology’. The long-term goal of reducing the impact of unwanted by-products of industry can be attained by lowering the rate of material consumption. Likewise, McCaffrey (2002) suggested three alternatives to reduce the amount of carbon dioxide (CO2) emissions by the cement industries, i.e. to decrease the amount of calcined material in cement, to decrease the amount of cement in concrete, and to decrease the number of buildings using cement.

[6]

2.2 FLY ASH :- According to the American Concrete Institute (ACI) Committee 116R, fly ash is defined as ‘the finely divided residue that results from the combustion of ground or powdered coal and that is transported by flue gasses from the combustion zone to the particle removal system’ (ACI Committee 232 2004). Fly ash is removed from the combustion gases by the dust collection system, either mechanically or by using electrostatic precipitators, before they are discharged to the atmosphere. Fly ash particles are typically spherical, finer than Portland cement and lime, ranging in diameter from less than 1 µm to no more than 150 µm.

The types and relative amounts of incombustible matter in the coal determine the chemical composition of fly ash. The chemical composition is mainly composed of the oxides of silicon (SiO2), aluminium (Al2O3), iron (Fe2O3), and calcium (CaO), whereas magnesium, potassium, sodium, titanium, and sulphur are also present in a lesser amount. The major influence on the fly ash chemical composition comes from the type of coal. The combustion of sub-bituminous coal contains more calcium and less iron than fly ash from bituminous coal. The physical and chemical characteristics depend on the combustion methods, coal source and particle shape.

The chemical compositions of various fly ashes show a wide range, indicating that there is a wide variations in the coal used in power plants all over the world (Malhotra and Ramezanianpour 1994).

Fly ash that results from burning sub-bituminous coals is referred as ASTM Class C fly ash or high calcium fly ash, as it typically contains more than 20 percent of CaO. On the other hand, fly ash from the bituminous and anthracite coals is referred as ASTM Class F fly ash or low calcium fly ash. It consists of mainly an aluminosilicate glass, and has less than 10 percent of CaO. The colour of fly ash can be tan to dark grey, depending upon the chemical and mineral constituents (Malhotra and Ramezanianpour 1994; ACAA 2003). The typical fly ash produced from Australian power stations is light to mid-grey in colour, similar to the colour of cement powder.

The majority of Australian fly ash falls in the category of ASTM Class F fly ash, and contains 80 to 85% of silica and alumina (Heidrich 2002).

Aside from the chemical composition, the other characteristics of fly ash that generally considered are loss on ignition (LOI), fineness and uniformity. LOI is a measurement of unburnt carbon remaining in the ash. Fineness of fly ash mostly depends on the operating conditions of coal crushers and the grinding process of the coal itself. Finer gradation generally results in a more reactive ash and contains less carbon.

In 2001, the annual production of fly ash in the USA was about 68 million tons. Only 32 percent of this was used in various applications, such as in concrete, structural fills, waste stabilisation/solidification etc. (ACAA 2003). Ash production in Australia in 2000 was approximated 12 million tons, with some 5.5 million tons have been utilised (Heidrich 2002). Worldwide, the estimated annual production of coal ash in 1998 was more than 390 million tons. The main contributors for this amount were China and India. Only about 14 percent of this fly ash was utilized, while the rest was disposed in landfills (Malhotra 1999). By the year 2010, the amount of fly ash produced worldwide is estimated to be about 780 million tons annually (Malhotra 2002). The utilization of fly ash, especially in concrete production, has significant environmental benefits, viz, improved concrete durability, reduced use of energy, diminished greenhouse gas production, reduced amount of fly ash that must be disposed in landfills, and saving of the other natural resources and materials (ACAA 2003).

FLY ASH WORKS

3.1 FLY ASH HELPS IN CONCRETE :principal mineralogical phases. These phases are Tricalcium Silicate–C2S (2CaO.SiO2), Tricalcium Aluminate(4CaO. Al2O3 Fe2O3). The setting and hardening of the OPC takes place as a result of reaction between these principal compounds and water.The reaction between these compounds and water are shown as under:

2C3S + 6H

Tricalcium silicate +Water

2C2S +4H

Dicalcium silicate +Water

The hydration rod s from C S and C S are similar but quantity of calcium hydroxide (lime) released is higher inC3S as compared to C

The reaction of C3A with water takes place in presencgypsum present in OPC. This reaction is very fast and is shown as under:

C3A +3(CSH2)

Tricalcium alluminate + Gypsum

C3A + CSH2

[7]

FLY ASH WORKS WITH CEMENT

3.1 FLY ASH HELPS IN CONCRETE :- Ordinary Portland Cement (OPC) is a product of four principal mineralogical phases. These phases are Tricalcium Silicate-C3S (3CaO.SiO

), Tricalcium Aluminate- C3A (3CaO.Al2O3) and Tetracalcium alumino). The setting and hardening of the OPC takes place as a result of reaction between

these principal compounds and water.The reaction between these compounds and water are shown as

+ 6H C3S2H3

+Water C-S-H gel

+4H C3S2H3

Water C-S-H gel

The hydration rod s from C S and C S are similar but quantity of calcium hydroxide (lime) S as compared to C2S.

A with water takes place in presence of sulphate ions supplied by dissolution of gypsum present in OPC. This reaction is very fast and is shown as under:

+3(CSH2) +26H

Gypsum + Water

+ CSH2 +10H

Monosulphoaluminate hydrate

CHAPTER 3

Ordinary Portland Cement (OPC) is a product of four S (3CaO.SiO2), Dicalcium Silicate

) and Tetracalcium alumino-ferrite – C4AF ). The setting and hardening of the OPC takes place as a result of reaction between

these principal compounds and water.The reaction between these compounds and water are shown as

+3CH

Calcium hydroxide

+ CH

Calcium hydroxide

The hydration rod s from C S and C S are similar but quantity of calcium hydroxide (lime)

e of sulphate ions supplied by dissolution of

C3A(CS)3 H32

Ettringite

C3ACSH12

Monosulphoaluminate hydrate

Tetracalcium alumino-ferrite forms hydration product similar to those of Csubstituting partially for alumina in the crystal

Above reactions indicate that during the hydration process of cement, lime is released out and remains as surplus in the hydrated cement. This leached out surplus lime renders deleterious effect toconcrete such as make the concrete porous, give chance to the development of microthe bond with aggregates and thus affect the durability of concrete.

If fly ash is available in the mix, this surplus lime becomes the source for pozzolfly ash and forms additional C-S-H gel having similar binding properties in the concrete as those

produced by hydration of cement paste. The reaction of fly ash with surplus lime continues as long as lime is present in the pores of liquid cement paste.

3.1.1 REDUCED HEAT OF HYDRATION :contact, a chemical reaction initiates that produces binding material and con solidates the concrete mass.

The process is exothermic and heat is released whfly ash is present in the concrete mass, it plays dual role for the strength development. Fly ash reacts with released lime and produces binder as explained above and render additional strength to the concreteThe unreactive portion of fly ash act as micro aggregates and fills up the matrix to render packing effect and results in increased strength.

The large temperature rise of concrete mass exerts temperature stresses and can lead micro crackes. When fly ash is used as part of cementitious material, quantum of heat liberated is low and staggers through pozzolanic reactions and thus reduces microconcrete mass.

[8]

ferrite forms hydration product similar to those of Csubstituting partially for alumina in the crystal structures of ettringite and monosulpho

Above reactions indicate that during the hydration process of cement, lime is released out and remains as surplus in the hydrated cement. This leached out surplus lime renders deleterious effect toconcrete such as make the concrete porous, give chance to the development of microthe bond with aggregates and thus affect the durability of concrete.

If fly ash is available in the mix, this surplus lime becomes the source for pozzolH gel having similar binding properties in the concrete as those

produced by hydration of cement paste. The reaction of fly ash with surplus lime continues as long as d cement paste.

3.1.1 REDUCED HEAT OF HYDRATION : - In concrete mix, when water and cement come in contact, a chemical reaction initiates that produces binding material and con solidates the concrete mass.

The process is exothermic and heat is released which increases the temperature of the mass When fly ash is present in the concrete mass, it plays dual role for the strength development. Fly ash reacts with released lime and produces binder as explained above and render additional strength to the concreteThe unreactive portion of fly ash act as micro aggregates and fills up the matrix to render packing effect

The large temperature rise of concrete mass exerts temperature stresses and can lead micro fly ash is used as part of cementitious material, quantum of heat liberated is low and

staggers through pozzolanic reactions and thus reduces micro-cracking and improves soundness of

ferrite forms hydration product similar to those of C3A, with iron structures of ettringite and monosulpho-aluminate hydrate.

Above reactions indicate that during the hydration process of cement, lime is released out and remains as surplus in the hydrated cement. This leached out surplus lime renders deleterious effect to concrete such as make the concrete porous, give chance to the development of micro- cracks, weakening

If fly ash is available in the mix, this surplus lime becomes the source for pozzolanic reaction with H gel having similar binding properties in the concrete as those

produced by hydration of cement paste. The reaction of fly ash with surplus lime continues as long as

In concrete mix, when water and cement come in contact, a chemical reaction initiates that produces binding material and con solidates the concrete mass.

ich increases the temperature of the mass When fly ash is present in the concrete mass, it plays dual role for the strength development. Fly ash reacts with released lime and produces binder as explained above and render additional strength to the concrete mass. The unreactive portion of fly ash act as micro aggregates and fills up the matrix to render packing effect

The large temperature rise of concrete mass exerts temperature stresses and can lead micro fly ash is used as part of cementitious material, quantum of heat liberated is low and

cracking and improves soundness of

[9]

3.1.2 WORKABILITY OF CONCRETE :- Fly ash particles are generally spherical in shape and reduces the water requirement for a given slump. The spherical shape helps to reduce friction between aggregates and between concrete and pump line and thus increases workability and improve pumpability of concrete. Fly ash use in concrete increases fines volume and decreases water content and thus reduces bleeding of concrete.

3.1.3 PERMEABILITY AND CORROSION PROTECTION :- Water is essential constituent of concrete preparation. When concrete is hardened, part of the entrapped water in the concrete mass is consumed by cement mineralogy for hydration. Some part of entrapped water evaporates, thus leaving porous channel to the extent of volume occupied by the water. Some part of this porous volume is filled by the hydrated products of the cement paste. The remaining part of the voids consists capillary voids and give way for ingress of water. Similarly,

the liberated lime by hydration of cement is water-soluble and is leached out from hardened concrete mass, leaving capillary voids for the ingress of water. Higher the water cement ratio, higher will be the porosity and thus higher will be the permeability. The permeability makes the ingress of moisture and air easy and is the cause for corrosion of reinforcement. Higher permeability facilitate ingress of chloride ions into concrete and is the main cause for initiation of chloride induced corrosion.

Additional cementitious material results from reaction between liberated surplus lime and fly ash, blocks these capillary voids and also reduces the risk of leaching of surplus free lime and thereby reduces permeability of concrete.

3.2 HOW FLY ASH CAN BE USED IN CEMENT CONCRETE? :- The main objective of using fly ash in most of the cement concrete applications is to get durable concrete at reduced cost, which can be achieved by adopting one the following two methods:

I. Using Fly ash based Portland Pozzolana Cement (PPC) conforming to IS:1489 Part-1 in place of Ordinary Portland Cement

II. Using fly ash as an ingredient in cement concrete.

The first method is most simple method, since PPC is factory-finished product and does not requires any additional quality check for fly ash during production of concrete. In this method the proportion of fly ash and cement is, however, fixed and limits the proportioning of fly ash in concrete mixes.

The addition of fly ash as an additional ingredients at concrete mixing stage as part replacement of OPC and fine aggregates is more flexible method. It allows for maximum utilization of the quality fly ash as an important component (cementitious and as fine aggregates) of concrete.

There are three basic approaches for selecting the quantity of fly ash in cement concrete:

I. Partial Replacement of Ordinary Portland Cement (OPC)- the simple replacement method. II. Addition of fly ash as fine aggregates the addition method.

III. Partial replacement of OPC, fine aggregate, and water- a modified replacement method.

[10]

3.2.1 SIMPLE REPLACEMENT METHOD:- In this method a part of the OPC is replaced by fly ash on a one to one basis by mass of cement. In this process, the early strength of concrete is lower and higher strength is developed after 56-90 days. At early ages fly ash exhibits very little cementing value. At later ages when liberated lime resulting from hydration of cement, reacts with fly ash and contributes considerable strength to the concrete. This method of fly ash use is adopted for mass concrete works where initial strength of concrete has less importance compared to the reduction of temperature rise.

3.2.2 ADDITION METHOD:- In this method, fly ash is added to the concrete without corresponding reduction in the quantity of OPC. This increases the effective cementitious content of the concrete and exhibits increased strength at all ages of the concrete mass. This method is useful when there is a minimum cement content criteria due to some design consideration.

3.2.3 MODIFIED REPLACEMENT METHOD:- This method is useful to make strength of fly ash concrete equivalent to the strength of control mix (without fly ash concrete) at early ages i.e. between 3 and 28 days. In this method fly ash is used by replacing part of OPC by mass along with adjustment in quantity of fine aggregates and water. The concrete mixes designed by this method will have a total weight of OPC and fly ash higher than the weight of the cement used in comparable to control mix i.e. without fly ash mix. In this method the quantity of cementitious material (OPC + Fly ash) is kept higher than quantity of cement in control mix (without fly ash) to offset the reduction in early strength.

[11]

CHAPTER 4

EFFECTS

4.1 EFFECT OF FLY ASH ON CARBONATION OF CONCRETE:- Carbonation phenomenon in concrete occurs when calcium hydroxides (lime) of the hydrated Portland Cement react with carbon dioxide from atmospheres in the presence of moisture and form calcium carbonate. To a small extent, calcium carbonate is also formed when calcium silicate and aluminates of the hydrated Portland cement react with carbon dioxide from atmosphere. Carbonation process in concrete results in two deleterious effects (i) shrinkage may occur (ii) concrete immediately adjacent to steel reinforcement may reduce its resistance to corrosion. The rate of carbonation depends on permeability of concrete, quantity of surplus lime and environmental conditions such as moisture and temperature. When fly ash is available in concrete; it reduces availability of surplus lime by way of pozzolanic reaction, reduces permeability and as a result improves resistance of concrete against carbonation phenomenon.

4.2 SULPHATE ATTACK:- Sulphate attacks in concrete occur due to reaction between sulphate from external origins or from atmosphere with surplus lime leads to formation of etrringite, which causes expansion and results in volume destabilization of the concrete. Increase in sulphate resistance of fly ash concrete is due to continuous reaction between fly ash and leached out lime, which continue to form additional C-S-H gel. This C-S-H gel fills in capillary pores in the cement paste, reducing permeability and ingress of sulphate ions.

4.3 CORROSION OF STEEL:- Corrosion of steel takes place mainly because of two types of attack. One is due to carbonation attack and other is due to chloride attack. In the carbonation attack, due to carbonation of free lime, alkaline environment in the concrete comes down which disturbs the passive iron oxide film on the reinforcement. When the concrete is permeable, the ingress of moisture and oxygen infuse to the surface of steel initiates the electrochemical process and as a result-rust is formed. The transformation of steel to rust increases its volume thus resulting in the concrete expansion, cracking and distress to the structure.

In the chloride attack, Chloride ion becomes available in the concrete either through the dissociation of chlorides-associated mineralogical hydration or infusion of chloride ion. The sulphate attack in the concrete decomposes the chloride mineralogy thereby releasing chloride ion. In the presence of large amount of chloride, the concrete exhibits the tendency to hold moisture. In the presence of moisture and oxygen, the resistivity of the concrete weakens and becomes more permeable thereby inducing further distress. The use of fly ash reduces availability of free limes and permeability thus result in corrosion prevention.

4.4 REDUCED ALKALI- AGGREGATE REACTION:- Certain types of aggregates react with available alkalis and cause expansion and damage to concrete. These aggregates are termed as reactive aggregates. It has been established that use of adequate quantity of fly ash in concrete reduces the amount of alkali aggregate reaction and reduces/ eliminates harmful expansion of concrete. The reaction between the siliceous glass in fly ash and the alkali hydroxide of Portland cement paste consumes alkalis thereby reduces their availability for expansive reaction with reactive silica aggregates.

In a nutshell, it can be summarized that permeability and surplus lime liberated during the hydration of Portland cement are the root causes for deleterious effect on the concrete. Impermeability is the foremost defensive mechanism for making concrete more durable and is best achieved by using fly ash as above.

[12]

4.5 ENVIRONMENTAL BENEFITS OF FLY ASH USE IN CONCRE TE :- Use of fly ash in concrete imparts several environmental benefits and thus it is ecofriendly. It saves the cement requirement for the same strength thus saving of raw materials such as limestone, coal etc required for manufacture of cement.Manufacture of cement is high-energy intensive industry. In the manufacturing of one tonne of cement, about 1 tonne of CO is emitted and goes to atmosphere. Less requirement of cement means less emission of CO2 result in reduction in green house gas emission.

Due to low calorific value and high ash content i n Indian Coal, thermal power plants in India, are producing huge quantity of fly ash. This huge quantity is being stored / disposed off in ash pond areas. The ash ponds acquire large areas of agricultural land. Use of fly ash reduces area requirement for pond, thus saving of good agricultural land.

4.6 PHYSICAL PROPERTIES:- The fly ash particles are generally glassy, solid or hollow and spherical in shape. The hollow spherical particles are called as cenospheres. The fineness of individual fly ash particle rage from 1 micron to 1 mm size. The fineness of fly ash particles has a significant influence on its performance in cement concrete. The fineness of particles is measured by measuring specific surface area of fly ash by blaine's specific area technique. Greater the surface area more will be the fineness of fly ash. The other method used for measuring fineness of fly ash is dry and wet Sieving.

The specific gravity of fly ash varies over a wide range of 1.9 to 2.55.

4.7 POZZOLANIC PROPERTIES OF FLY ASH:- Fly Ash is a pozzolanic material which is defined as siliceous or siliceous and aluminous material which in itself possesses little or no cementitious value, chemically react with Calcium Hydroxide (lime) in presence of water at ordinary temperature and form soluble compound comprises cementitious property similar to cement.

The pozzolana term came from Roman. About 2,000 years ago, Roman used volcanic ash along with lime and sand to produce mortars, which possesses superior strength characteristics & resistances to corrosive water. The best variety of this volcanic ash was obtained from the locality of pozzoli and thus the volcanic ash had acquired the name of Pozzolana.

4.8 POZZOLANIC ACTIVITY:- Pozzolanic activity of fly ash is an indication of the lime fly ash reaction. It is mostly related to the reaction between reactive silica of the fly ash and calcium hydroxide which produce calcium silicate hydrate (C-S-H) gel which has binding properties. The alumina in the pozzolana may also react in the fly ash lime or fly ash cement system and produce calcium aluminate hydrate, ettringite, gehlenite and calcium monosulpho-aluminate hydrate. Thus the sum of reactive silica and alumina in the fly ash indicate the pozzolanic activity of the fly ash.

SALIENT ADVANTAGE OF USING FLY ASH IN CEMENT CONCRE TE

� Reduction in heat of hydration and thus reduction of thermal cracks and improves soundness of concrete mass.

� Improved workability / pumpabilty of concrete

� Converting released lime from hydration of OPC into additional binding material – contributing additional strength to concrete mass.

� Pore refinement and grain refinement due to reaction between fly ash and liberated lime improves impermeability.

� Improved impermeability of concrete mass increases resistance against ingress of moisture and harmful gases result in increased durability.

� Reduced requirement of cement for same strength thus reduced cost of concrete.

[13]

CHAPTER 5

QUALITY

5.1 BUREAU OF INDIAN STANDARD:- To utilize fly ash as a Pozzolana in Cement concrete and Cement Mortar, Bureau of Indian Standard (BIS) has formulated IS: 3812 Part - 1 2003. In this code quality requirement for siliceous fly ash (class F fly ash) and calcareous fly ash (class C fly ash) with respect its chemical and physical composition have been specified. These requirements are given in table 1 & table 2:

TABLE 5.1

CHEMICAL REQUIREMENTS

SL.

NO.

CHARACTERISTIC REQUIREMENTS

SILICEOUS

FLY ASH

CALCAREOUS

FLY ASH

I Silicon dioxide (SiO2) + Aluminium oxide (Al 2O3) + Iron oxide (Fe2O3), in percent by mass, Min..

70 50

II Silicon dioxide in percent by mass, Min. 35 25

III Reactive Silica in percent by mass, Min (Optional Test)

20 20

IV Magnesium Oxide (MgO), in percent by mass, Max. .

5.0 5.0

V Total sulphur as sulphur trioxide (SO3), in percent by mass, Max.

3.0 3.0

VI Available alkalis as Sodium oxide (Na2O), percent by mass, Max.

1.5 1.5

VII Total Chlorides in percent by mass, Max 0.05 0.05

VIII Loss on Ignition, in percent by mass, Max. 5.0 5.0

[14]

TABLE 5.2

PHYSICAL REQUIREMENTS

5.2 ASTM INTERNATIONAL FOR FLY ASH:- ASTM International C-618-03 specifies the chemical composition and physical requirements for fly ash to be used as a mineral admixture in concrete. The standard requirements are given in table 3 and table 4:

TABLE 5.3

CHEMICAL REQUIREMENTS

SL.

NO

CHARACTERISTICS REQUIREMENTS FOR SILICEOUS FLY ASH AND CALCAREOUS FLY ASH

I Fineness- Specific surface in m2/kg by Blaine’s permeability method, Min.

320

II Particles retained on 45 micron IS sieve (wet sieving) in percent, Max. (Optional Test)

34

III Lime reactivity – Average compressive strength in N/mm2, Min.

4.5

IV Compressive strength at 28 days in N/mm2, Min. Not less than 80 percent of the strength

of corresponding plain cement mortar cubes

V Soundness by autoclave test -Expansion of specimen in percent, Max.

0.8

SL.

NO.

CHARACTERISTIC REQUIREMENTS

CLASS F(SILICEOUS FLY

ASH)

CLASS C (CALCAREOUS

FLYASH)

I Silicon dioxide (SiO2) + Aluminium oxide (Al2O3) + Iron oxide (Fe2O3), in percent by mass, Min..

70 50

II Sulfur trioxide (SO3), max. Percent 5.0 5.0

III Moisture content, max. ,percent 3.0 3.0

IV Loss on ignition, max., percent 6.0 6.0

[15]

TABLE 5.4

PHYSICAL REQUIREMENTS

SL.

NO

CHARACTERISTICS REQUIREMENTS FOR CLASS F &

CLASS C FLY ASH

I Fineness- amount retained when wetsieved on 45 micron (No. 325 ) sieve, Max., percent

34

II

Strength Activity index

With Portland Cement, at 7 days, min. ,percent of control

75C

With Portland cement, at 28 days, min, percent of control 75C

III Water requirement, max, percent of control 105

IV Soundness-Autoclave expansion or contraction, Max., percent

0.8

V

Uniformity Requirements:

The density and fineness of individual samples shall not vary from the average established by ten preceding tests, or by all preceding tests if the number is less than ten, by more than

Density, max. variation from average, percent..

5

5 Percent retained on 45 micron (no.325), max. variation, percentage points from average.

[16]

CHAPTER 6 MIX DESIGN

Cement Concrete is principally made with combination of cement (OPC / PPC/Slag), aggregate

and water. It may also contain other cementitious materials such as fly ash, silica fumes etc. and / or chemical admixture. Use of Fly ash along with cement helps to provide specific properties like reduced early heat of hydration, increased long term strength, increased resistance to alkali aggregate reaction and sulphate attack, reduced permeability, resistance to the intrusion of aggressive solutions and also economy. Chemical admixture are used to accelerate, retard, improve workability, reduce mixing water requirement, increase strength or alter other properties of the concrete.

6.1 CRITERIA FOR MIX DESIGN:- The selection of concrete proportions involves a balance between economy and requirements for workability and consistency, strength, durability, density and appearance for a particular application. In addition, when mass concrete is being proportioned, consideration is also given to heat of hydration.

6.2 ILLUSTRATIVE EXAMPLE OF CONCRETE MIX DESIGN (GRADE M 20):-

6.2.1 DESIGN STIPULATIONS:- i Characteristic Compressive Strength required in the field at 28 days 20 Mpa

ii Maximum size of aggregate 20mm(angular)

iii Degree of workability 0.90 Compacting factor

iv Degree of quality control Good

v Type of Exposure Mild

6.2.2 TEST DATA FOR MATERIAL:- i Specific gravity of cement 3.15

ii Compressive strength of cement at 7 days Satisfies the requirement of IS:269-1989

iii Specific gravity of coarse aggregates 2.60

Specific gravity of fine aggregates 2.60

iv Water absorption of coarse aggregate 0.50%

Water absorption of fine aggregate 1.0%

v Free surface moisture of coarse aggregate Nil

Free surface moisture of fine aggregate 2.0%

6.2.3 SIEVE ANALYSIS OF COARSE AGGREGATE:Sieve Size(mm)

Analysis of coarse aggregate fractions(%passing)

I II

20 100 100

10 0 71.20

4.75 - 9.40

2.36 - -

6.2.4 SIEVE ANALYSIS OF FINE AGGREGATE:Sieve Sizes Fine aggregate (%passing)

4.75 mm 100

2.36 mm 100

1.18 mm 93

600 micron 60

300 micron 12

150 micron 2

[17]

SIEVE ANALYSIS OF COARSE AGGREGATE:- of coarse aggregate Percentage of different fractions

I (60%) II (40%) Combined (100%)

60 40 10

0 28.5 28.5

- 3.7 3.7

- - -

SIEVE ANALYSIS OF FINE AGGREGATE:- Fine aggregate (%passing) Remarks

100 Conforming to grading zone III of table 4 IS: 385100

93

60

12

2

Remark

Combined (100%)

Conforming to table 2, IS: 383-1970

Conforming to grading zone III of table 4 IS: 385-1970

6.2.5 TARGET MEAN STRENGTH OF CONCRETE:

characteristic cube strength is 20 + 1.65 x 4 = 26.6 MPa (refer Table

6.2.6 SELECTION OF WATERtarget mean strength of 26.6 MPa is 0.50. This is lower than the maximum value of 0.55 prescribed for ‘Mild’ exposure. (refer Table 6.3) adopt W/C ratio of 0.50.

[18]

TARGET MEAN STRENGTH OF CONCRETE:- The target mean strength for specified

characteristic cube strength is 20 + 1.65 x 4 = 26.6 MPa (refer Table 6.1 & Table 6.2 for values of t

SELECTION OF WATER-CEMENT RATIO:- The water-cement ratio required for the target mean strength of 26.6 MPa is 0.50. This is lower than the maximum value of 0.55 prescribed for

) adopt W/C ratio of 0.50.

The target mean strength for specified

2 for values of t & s)

cement ratio required for the target mean strength of 26.6 MPa is 0.50. This is lower than the maximum value of 0.55 prescribed for

6.2.7 SELECTION OF WATER AND SAND CONTENT:

maximum size aggregate, sand conforming to grading= 186 kg and sand content as percentage

For change in value in waterfollowing adjustment is required.

[19]

SELECTION OF WATER AND SAND CONTENT:-From Table maximum size aggregate, sand conforming to grading Zone II, water content per cubic metre of concrete = 186 kg and sand content as percentage of total aggregate by absolute volume = 35 per cent.

water-cement ratio, compacting factor, for sand belonging to

From Table 6.4, for 20 mm Zone II, water content per cubic metre of concrete

of total aggregate by absolute volume = 35 per cent.

cement ratio, compacting factor, for sand belonging to Zone III,

Change in condition(See Table 6.5)

For decrease in water-cement ratio by(0.60

For increase in compacting factor(0.9

For sand conforming to Zone III of Table 4, IS: 383

Total

Therefore, required sand content as percentage of total aggregate by absolute volume= 35 Required water content = 186 + 5.58 = 191.6 1/m

6.2.8 DETERMINATION OF CEMENT CONTENT:Water-cement ratio = 0.50 Water = 191.6 litre ∴ Cement =1916÷0.50 = 383 kg/m3This cement content is adequate for ‘mild’ expos

6.2.9 DETERMINATION OF COARSE AND FINE AGGREGATE CONTENTS:

Table 6.6, for the specified maximum size of aggregate of 20 mm, the amount of concrete is 2 per cent. Aggregate content can be determined from the following equations :

Where, V = absolute volume of fresh concrete, which is equal to gross volumevolume of entrapped air, W = Mass of water (kg) per m3 of concreteC = Mass of cement (kg) per m3 of concreteSc = Specific gravity of cement P = Ratio of FA to total aggregate by absolute volumefa, Ca = Total masses of FA and CA (kg) per mSfa, Sca = Specific gravities of saturated, surface dry fine aggregate and coarse aggregate

[20]

Percent adjustment required

Water Content Sand in Total aggregate

by(0.60-0.50) that is 0.10 0 - 2.0

For increase in compacting factor(0.9-0.8) that is 0.10 + 3 0

For sand conforming to Zone III of Table 4, IS: 383-1970 0 - 1.5

Total + 3 - 3.5

Therefore, required sand content as percentage of total aggregate by absolute volume= 35 Required water content = 186 + 5.58 = 191.6 1/m3

DETERMINATION OF CEMENT CONTENT:-

=1916÷0.50 = 383 kg/m3 This cement content is adequate for ‘mild’ exposure condition. (refer Table 6.3)

DETERMINATION OF COARSE AND FINE AGGREGATE CONTENTS:, for the specified maximum size of aggregate of 20 mm, the amount of entra

Aggregate content can be determined from the following equations :

� � ��

��1

��

� ��

1

1000

�� 1 �

� ��

��

� �

, V = absolute volume of fresh concrete, which is equal to gross volume (m3) minus the

of concrete of concrete

P = Ratio of FA to total aggregate by absolute volume = Total masses of FA and CA (kg) per m3 of concrete respectively and

= Specific gravities of saturated, surface dry fine aggregate and coarse aggregate

Percent adjustment required

Sand in Total aggregate

2.0

1.5

3.5

Therefore, required sand content as percentage of total aggregate by absolute volume= 35 – 3.5 = 31.5%

DETERMINATION OF COARSE AND FINE AGGREGATE CONTENTS:- From entrapped air in the wet

Aggregate content can be determined from the following equations :

) minus the

= Specific gravities of saturated, surface dry fine aggregate and coarse aggregate respectively.

[21]

Therefore, 0.98 = �191.6 ��

�.��

�

�.��

�

�.��

�

��

fa = 546 kg/m3, and

Ca= ��.��

�.�� 546 �

�.�

�.� = 1188 kg/m3

fa = 546 kg/m3, and Ca = 1188 kg/m3. The mix proportion then becomes: Water Cement Fine Aggregate Coarse Aggregate 191.6 383 Bags 546 Kg 1181 Kg 0.50 1 1.425 3.10

[22]

CHAPTER 7

THE COMPRESSIVE STRENGTH OF CUBIC CONCRETE SPECIMENS

BS 1881: PART 116: 1983

7.1 SCOPE: The test method covers determination of compressive strength of cubic concrete specimens. It consists of applying a compressive axial load to molded cubes at a rate which is within a prescribed range until failure occurs. The compressive strength is calculated by dividing the maximum load attained during the test by the cross sectional area of the specimen.

7.2 APPARATUS:

I. Weights and weighing device. II. Tools and containers for mixing.

III. Tamper (square in cross section) IV. Testing machine. V. Three cubes (150 mm side)

7.3 PROCEDURE:

I. Prepare a concrete mix as mentioned in (test No. 3 ) with the proportions suggested Such as: 1: 2: 3 with w/c = 55% by mechanical mixer.

II. Prepare three testing cubes; make sure that they are clean and greased or oiled thinly. III. Metal molds should be sealed to their base plates to prevent loss of water. IV. Fill the cubes in three layers, tamping each layer with (35) strokes using a tamper, square in cross-

section with 2.54 cm side and 38.1 cm length, weighing 1.818 kg. V. While filling the molds, occasionally stir and scrape together the concrete remaining in the mixer

to keep the materials from separating. VI. Fill the molds completely, smooth off the tops evenly, and clean up any concrete outside the

cubes. VII. Mark the specimens by a slip of paper on which is written the date and the Specimen

identification. Leave the specimens in the curing room for 24 hours. VIII. After that open the molds and immerse the concrete cubes in a water basin for 7 days.

IX. Before testing, ensure that all testing machine bearing surfaces are wiped clean. X. Carefully center the cube on the lower platen and ensure that the load will be applied to two

opposite cast faces of the cube. XI. Without shock, apply and increase the load continuously at a nominal rate within the range of ( 0.2

N/mm2.s to 0.4 N/mm2.s ) until no greater load can be sustained. On manually controlled machines, as failure is approached, the loading rate will decrease, at this stage operate the controls to maintain, as far as possible, the specified loading rate. Record the maximum load applied to each cube.

NOTE:When the cubes are surface dry, or have not been cured in water, immerse them in water, for a minimum of 5 minutes, before testing. They must be tested while they are still wet.

7.4 TYPE OF FAILURE :-Record any unusual feature in the type of failure. Refer to fig.(7.1) for examples of satisfactory failure and to fig. (7.2) for examples of some unsatisfactory failures.

NOTE: Unsatisfactory failures are usually caused by insufficient attention to the details of making and testing specimens, such as bad molds, bad made specimens or mis placement of cubes in the testing machine or machine fault.

7.5 CALCULATIONS :- Calculate the cross-sectional area of the

Calculate the compressive strength of each cube by dividing thearea. Calculate the average for the three cubes.

[23]

sectional area of the cube face from the checked nominalCalculate the compressive strength of each cube by dividing the maximum load by the cross

Calculate the average for the three cubes.

cube face from the checked nominal dimensions. maximum load by the cross-sectional

TABULATION FOR Table:-8.1. NORMAL CEMENT CONCRETE :

Grade of Concrete

Days Crushing Load(KN)

15

7

15

14

15

28

[25]

TABULATION FORM OF TESTED RESULTS

8.1. NORMAL CEMENT CONCRETE :-

Crushing Load(KN)

Average Crushing Load(KN)

Area(mm2)

308 324.33

150*150 346

319 399

422.67

150*150 418 451 508

519.33

150*150 533 517

CHAPTER 8

STED RESULTS

Crushing Strength(N/mm2)

14.44

18.79

23.08

Table:-8.2. 5% FLY ASH MIXED CEMENT CONCRETE

Grade of Concrete

Days

15

7

15

14

15

28

[26]

8.2. 5% FLY ASH MIXED CEMENT CONCRETE

Crushing Load(KN)


Area(mm2)

284 319.00

150*150 330

343 416

415.00

150*150 398 431 483

511.33

150*150 513 538


14.18

18.44

22.73


Grade of Concrete


15

7

281307285

15

14

304313314

15

28

313327359

[27]

ASH MIXED CEMENT CONCRETE

Crushing Load(KN)


Area(mm2) Crushing Strength(N/mm

281 291.00

150*150 307

285 304

310.33

150*150 313 314 313

333.00

150*150 327 359


12.93

13.79

14.80


Grade of Concrete


15

7

237238263

15

14

208223230

15

28

197201210

[28]


Crushing Load(KN)



237 246.00

150*150 238

263 208

220.33

150*150 223 230 197

202.67

150*150 201 210


10.93

9.79

9.01

Table:-8.5. NORMAL CEMENT CONCRETE

Grade of Concrete


20

7

415420437

20

14

516527546

20

28

606615637

[29]

8.5. NORMAL CEMENT CONCRETE

Crushing Load(KN)



415 424.00

150*150 420

437 516

529.67

150*150 527 546 606

619.33

150*150 615 637


18.84

23.54

27.52


Grade of Concrete


20

7

408412422

20

14

517523536

20

28

598602593

[30]


Crushing Load(KN)



408 414.00

150*150 412

422 517

525.33

150*150 523 536 598

597.67

150*150 602 593


18.40

23.34

26.56


Grade of Concrete


20

7

379382388

20

14

370376396

20

28

373381382

[31]


Crushing Load(KN)



379 383.00

150*150 382

388 370

380.67

150*150 376 396 373

378.67

150*150 381 382


17.02

16.91

16.82


Grade of Concrete


20

7

321330329

20

14

260276274

20

28

257267281

[32]

ASH MIXED CEMENT CONCRETE

Crushing Load(KN)



321 326.67

150*150 330

329 260

270.00

150*150 276 274 257

268.33

150*150 267 281


14.52

12.00

11.93

Table:-8.9. NORMAL CEMENT CONCRETE

Grade of Concrete


25

7

538576548

25

14

631601611

25

28

741708749

[33]

CEMENT CONCRETE

Crushing Load(KN)



538 554.00

150*150 576

548 631

614.33

150*150 601 611 741

732.77

150*150 708 749


24.62

27.30

32.56


Grade of Concrete


25

7

53855

25

14

6579629

25

28

7693731

[34]


Crushing Load(KN)



538 537.77

150*150 516

559 607

603.76

150*150 579 629 714

712.77

150*150 693 731


23.90

26.83

31.67


Grade of Concrete


25

7

489502523

25

14

466491437

25

28

430466412

[35]


Crushing Load(KN)



489 504.00

150*150 502

523 466

464.46

150*150 491 437 430

436.00

150*150 466 412


22.40

20.64

19.38


Grade of Concrete


25

7

367396411

25

14

369346318

25

28

315337362

[36]


Crushing Load(KN)



367 391.33

150*150 396

411 369

344.33

150*150 346 318 315

338.00

150*150 337 362


17.39

15.30

15.02

COMPARISON BETWEEN NORMAL CEMENT CONCRETE AND FLY ASH MIXED CEMENT CONCRETE:-

[37]

COMPARISON BETWEEN NORMAL CEMENT CONCRETE AND FLY ASH MIXED COMPARISON BETWEEN NORMAL CEMENT CONCRETE AND FLY ASH MIXED


[38]

COMPARISON BETWEEN NORMAL CEMENT CONCRETE AND FLY ASH MIXED COMPARISON BETWEEN NORMAL CEMENT CONCRETE AND FLY ASH MIXED


[39]

BETWEEN NORMAL CEMENT CONCRETE AND FLY ASH MIXED BETWEEN NORMAL CEMENT CONCRETE AND FLY ASH MIXED

[40]

CHAPTER 9

CONCLUSIONS

Based on the experimental work reported in this study, the following conclusions are drawn:

1. Higher concentration (in terms of molar) of sodium hydroxide solution results in higher compressive strength of fly ash-based concrete.

2. Higher the ratio of sodium silicate-to-sodium hydroxide ratio by mass, higher is the compressive strength of fly ash-based concrete.

3. As the curing temperature in the range of 30oC to 90oC increases, the compressive strength of fly ash-based concrete also increases.

4. Longer curing time, in the range of 4 to 96 hours (4 days), produces higher compressive strength of fly ash-based concrete. However, the increase in strength beyond 24 hours is not significant.

5. The addition of naphthalene sulphonate-based super plasticizer up to approximately 4% of fly ash by mass, improves the workability of the fresh fly ash-based concrete with very little effect on the compressive strength of hardened concrete.

6. The slump value of the fresh fly-ash-based concrete increases with the increase of extra water added to the mixture.

7. The Rest Period, defined as the time taken between casting of specimens and the commencement of curing, of up to 5 days increases the compressive strength of hardened fly ash-based concrete. The increase in strength is substantial in the first 3 days of Rest Period.

8. The fresh fly ash-based concrete is easily handled up to 120 minutes without any sign of setting and without any degradation in the compressive strength.

9. As the ratio of water-to- solids by mass increases, the compressive strength of fly ash-based concrete decreases.

10. The compressive strength of heat-cured fly ash-based concrete does not depend on age.

11. Prolonged mixing time of up to sixteen minutes increases the compressive strength of fly ash-based concrete.

12. The average density of fly ash-based concrete is similar to OPC concrete. 13. From Fig 8.13, 8.14, 8.15 shows that with adding 10%, 20% Fly Ash the

compressive strength will decrease the age of Concrete. 14. Increase the percentage of Fly Ash, the Crushing Strength will decrease but in

addition of 5% Fly Ash the Crushing Strength of a concrete is more or less equal to the grade of Concrete.

[41]

9.1 RECOMMENDATIONS FOR FUTURE RESEARCH:-To date, the reaction mechanism of fly ashisation is still not clear. Fundamental research in this area would increase the potential of the material. For example, a study is needed to identify the scientific reason for increase in strength after a longer resting period, and to investigate the role of water in fly ashisation.

Although the present work identified many salient parameters that influence the properties of fresh and hardened fly ash-based concrete, a large database should be built on the engineering properties of various mixtures using fly ash from different sources. Such a database may identify additional parameters, and lead to familiarise the utilisation of this material in many applications.

Further research should identify possible applications of fly ash technology. This would lead to research areas that are specifically oriented towards applications. The fly ash technology has the potential to go beyond making concrete; there could be possibilities in other areas of infrastructure needed by the community.

[42]

REFERENCES

1. Concrete Technology (Theory and Practice)-M.S. Shetty. 2. Concrete Technology Laboratory Manual-Balsam J.M. Farid (Al-Tahadi

University) 3. IS 3812-2003, Pulverized FuelAsh specification, part 1 for use as pozzolana in

cement, cement mortar and concrete. 4. IS456-2000 Plain &Reinforced Concrete Code of Practice. 5. IS: 269 -1989 - Ordinary Portland Cement - 33 Grade (Reaffirmed 2004) 6. IS: 8112-1989 - 43 Grade Ordinary Portland Cement (Reaffirmed 2005) 7. IS: 12269-1987 - 53 Grade Ordinary Portland Cement (Reaffirmed 2004) 8. IS: 1489 part-1 1991 - Portland Pozzolana Cement fly ash based (Reaffirmed

2005) 9. IS: 1489 part-2 1991 - Portland Pozzolana Cement calcined clay based

(Reaffirmed 2005) 10. IS: 455-1989 - Portland Slag Cement (Reaffirmed 2005) 11. ASTM International C: 618-03 Standard specification for coal Fly ash and Raw or

Calcined Natural Pozzolana for use in Concrete. 12. V. M. Malhotra and AA Ramezanianpour March 1994, FlyAsh In Concrete 13. Fly ash in concrete (Properties and Performance) - Report of Technical

Committee 67-FAB(RILEM) 14. Souvenir & Seminar Document, May 1996 Maharashtra India Chapter of ACI,

Use of Fly ash in concrete. 15. Dr.AK Chatterjee, Concrete for the 21 Century Meeting the challenges The Indian

Scenario Cement substitute Materials for concrete making The Indian Scenario. 16. MDAThomas, KB Cripwell and Pl Owens FlyAsh in concrete:An Overview of

more than 30 years of Experiences in the United Kingdom. 17. N. Bhanumathidas &N. Kalidas 2002-FlyAsh for Sustainable Development. 18. V V Gaikwad, V C Shelke and R А Gunjal Phoenixes from fly ash Three RCC

Dams for Ghatghar Project National Seminar cum Business Meet on use of Fly ash in Hydro Sector.

19. Mohammed Ashraf, Manish Mokal and J. Bhattacharya Fly Ash India 2005, New Delhi Use of Fly ash in high Performance Concrete & Self Compacting Concrete.

20. US department of Transportation, Federal Highway Administration -Fly ash Facts for Highway Engineers -TechnologyTransfer

21. Standard Practice for selecting Proportions for Normal, Heavyweight, and Mass Concrete (ACI 211.1-91)