Utilisation of Fly Ash in Cement Concrete

7172019 Utilisation of Fly Ash in Cement Concrete

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Reciept No 133

Utilisation of Fly Ash in Cement Concrete

Pramey M ZodeSE (Civil)

Sinhgad Academy of Engineering

Kondhwa(Bk) Pune-48 (India)E-mail pramey17gmailcom

Abstract - To meet the ever increasing demand of electricity

Thermal Power Plants (TPPs) are being set up all over the

world thereby resulting into more consumption of the coal

in these plants The disposal of ash derived from combustion

has become a major issue now-a-days The study of Fly Ash

as it is called has found that it can be used in various civil

engineering applications such as bricks and concrete

making This paper reviews the utilisation of Fly Ash as the

admixture in partial replacement of ordinary Portland

cement to upto 35 and even more upto 50 in High-Volume Fly Ash (HVFA) concrete which reduces the water

demand improves the workability minimizes cracking due

to thermal and drying shrinkage and enhances durability to

reinforcement corrosion sulphate attack and alkali-silica

expansion This admixing proves to be a best filler material

which also reduce overall cost of construction and act as an

eco-friendly material

IINTRODUCTION

Ash is a residue resulting from combustion of pulverised

coal or lignite in Thermal Power Plants (TPPs) About 80 oftotal ash is in finely divided form which is carried away with

flue gases and is collected by electrostatic precipitator or other

suitable technology This ash is called Fly Ash or chimney

Ash or Hopper Ash In an industrial context fly ash usually

refers to ash produced as an industrial by-product during

combustion of coal in TPPs

Fly ash is a fine (85 of its mass passing through a 45983221m

screen) pozzolaneous or a siliceous andor aluminous glassy

powdered material having micron-sized earth elements which

in the presence of water and lime will react to form a

cementitous material It consists of inorganic materials mainly

silica and alumina with some quantum of organic material in

the form of unburnt carbon Fly ash also contains

environmental toxins in significant amounts including arsenic

(434 ppm) barium (806 ppm) beryllium (5 ppm) boron (311

ppm) cadmium (34 ppm) chromium (136 ppm) chromium

VI (90 ppm) cobalt (359 ppm) copper (112 ppm) fluorine

(29 ppm) lead (56 ppm) manganese (250 ppm) nickel

(776ppm) selenium (77 ppm) strontium (775 ppm)

thallium (9 ppm) vanadium (252 ppm) and zinc (178 ppm)

IISOURCES OF FLY ASH IN INDIA

According to National Thermal Power Corporation

(NTPC) coal is used for approximately 623 of electric

power generation in India According to Central Electricity

Authority of India there are around 83 major coal fired

thermal power plants in India As per the Ministry of Power

Statistics the total installed generating capacity (TPPs) is

about 79838 MW In addition to this there are more than

1800 selected industrial units which have TPPs of gt1MW

capacity These are the chief sources of fly ash in India

IIIASH CONTENT IN INDIAN COAL

The quality of coal depends upon its rank and grade The

coal rank arranged in an ascending order of carbon contents is

Lignite --gt sub-bituminous coal --gt bituminous coal --gt

anthracite

Indian coal is of mostly sub-bituminous rank followed by

bituminous and lignite (brown coal) Thus the ash content in

Indian coal ranges from 35 to 50

IVCURRENT FLY ASH GENERATION IN INDIA

The current electricity generation in India is about 112058

MW 65-70 of which is thermal (mostly coal based)

According to an estimate 100000 MW capacity or more

would be required in the next 10 years due to continually

increasing demand for electricity Thus the present fly ash

generation in India is around 110 million tonnes year and is

set to continue at a high rate into the foreseeable future

VCURRENT FLY ASH UTILISATION

According to the MOEF Gazette Notification dated Sept

14 1999 the then existing power stations were to achieve

20 ash utilization within three years and 100 utilization in

15 years from the date of notification New Stations were to

achieve 30 ash utilization within 9 years at the rate of 10



ash utilization within 3 years Presently out of 110 million

tonnes of total ash generated only about 30 is being

utilized Therefore thermal power stations are under great

pressure to find useful applications of fly ash The technology

utilizing fly ash in high volume fly ash concrete can provide

an avenue for utilization of fly ash on a bulk scale

VI PROBLEMS DUE TO FLY ASH

Fly ash is a very fine powder and tends to travel far in the

air When not properly disposed it is known to pollute air andwater and causes respiratory problems when inhaled When it

settles on leaves and crops in fields around the power plant it

lowers the yield The conventional method used for disposal

of both fly ash and bottom ash is to convert them into slurry

for impounding in ash ponds around the thermal plants Thismethod entails long-term problems The severe problems that

arise from such dumping are

1) The construction of ash ponds requires vast tracts of land

This depletes land available for agriculture over a period of

time

2) When one ash pond fills up another has to be built at great

cost and further loss of agricultural land

3) Huge quantities of water are required to convert ash into

slurry During rains numerous salts and metallic content inthe slurry can leach down to the groundwater and contaminate

it

Taking into account these facts fly ash is being used in

various construction activities as a raw material In this paper

detailed study of use of fly ash in raw materials like Portland

cement is considered Further this paper reviews the use of

high volume fly ash in cement making for better yield

FLY ASH BASED POZZOLANA PORTLAND

CEMENT

IPOZZOLANS

Pozzolans are defined as silicious and aluminous materials

which in themselves possess little or no cementitious value

but in finely divided form and in the presence of moisture it

chemically react with calcium hydroxide at ordinary

temperature to form compounds possessing cementitious

properties

IICLASS F FLY ASH

The burning of harder older anthracite and bituminous

coal typically produces Class F fly ash This fly ash is

pozzolanic in nature and contains less than 20 lime (CaO)

Possessing pozzolanic properties the glassy silica and

alumina of Class F fly ash requires a cementing agent such

Portland cement quicklime or hydrated lime with the

presence of water in order to react and produce cementitious

compounds

Most of the state and federal specifications allow and even

encourage the use of Fly Ash especially when specificdurability requirements are needed Fly Ash has a long history

of use in concrete Fly Ash is used in about 50 of ready

mixed concrete Class C Fly Ash is used at dosages of 15 to40 by mass of the cementitious materials in the concrete

Class F is generally used at dosages of 15 to 30

IIIFLY ASH IN PORTLAND CEMENT

Owing to its pozzolanic properties fly ash is used as a

replacement for some of the Portland cement content of

concrete The use of fly ash as a pozzolanic ingredient was

recognized as early as 1914 although the earliest noteworthystudy of its use was in 1937Before its use was lost to the Dark

Ages Roman structures such as aqueducts or the Pantheon in

Rome used volcanic ash (which possesses similar properties to

fly ash) as pozzolan in their concrete As pozzolan greatly

improves the strength and durability of concrete the use of

ash is a key factor in their preservation

Use of fly ash as a partial replacement for Portland cement

is generally limited to Class F fly ashes It can replace up to

30 by mass of Portland cement and can add to the final

strength of concrete and increase its chemical resistance and

durability Recently concrete mix design for partial cement

replacement with High Volume Fly Ash (50 cement

replacement) has been developed For Roller Compacted

Concrete (RCC) [used in dam construction] replacement

values of 70 have been achieved with processed fly ash at

the Ghatghar Dam project in Maharashtra India Due to the

spherical shape of fly ash particles it can also increase

workability of cement while reducing water demand The

replacement of Portland cement with fly ash is considered by

its promoters to reduce the greenhouse gas footprint of

concrete as the production of one ton of Portland cement

produces approximately one ton of CO2 as compared to zeroCO2 being produced using existing fly ash New fly ash

production ie the burning of coal produces approximately

twenty to thirty tons of CO2 per ton of fly ash Since the

worldwide production of Portland cement is expected to reach

nearly 2 billion tons by 2012 replacement of any large portion

of this cement by fly ash can significantly reduce carbon

emissions associated with construction



Inclusion of Fly Ash in Portland cement based plastic

concrete mixes improves concrete workability by reducing the

water content for a given consistency The spherical particles

create a lsquoball bearingrsquo effect in the mix ndash thus improving

workability Fly Ash particles also fill voids in the mix which

reduces the water requirement for a given plastic consistency

Workable Fly Ash concrete places easier finishes better and

produces better lsquooff-formrsquo surfaces than plain Portland cement

concrete For use in concrete Fly Ash is referred to as a

lsquosupplementary cementitious materialrsquo

IVCHEMICAL COMPARISION OF FLY ASH AND

PORTLAND CEMENT

The chemical composition of fly ash is very similar to that

of portland cement

TABLE I

TYPICAL CHEMICAL COMPOUNDS

IN POZZOLANIC CLASS F FLY ASH AND PORTLAND CEMENT

Chemical

compound

Class F fly ash Cement

SiO 5490 260

Al2O3 2580 430

Fe2O3 690 240

CaO 870 6440

MgO 180 210

SO2 060 230

Na2O amp K 2O 060 060

The table above shows typical compound analysis for

Class F fly ash and ordinary portland cement A glance at the

table reveals

1 The same compounds exist in fly ash and portland cement

Those of fly ash are amorphous (glassy) due to rapid cooling

those of cement are crystalline formed by slower cooling

2 The major difference between fly ash and portland cement

is the relative quantity of each of the several compounds in

them Portland cement is rich in lime (CaO) while fly ash is

low Fly ash is rich in reactive silicates while Portland cement

has smaller amounts

Portland Cement + Water Calcium Silicate Hydrate

Free Lime (CaOH)

Portland Cement + Water

+ Fly Ash Calcium Silicate Hydrate

Portland cement is manufactured with CaO some of which

is released in a free state during hydration As much as 20

pounds of free lime is released during hydration of 100

pounds of cement This liberated lime forms the necessary

ingredient for reaction with fly ash silicates to form strong and

durable cementing compounds no different from those formed

during hydration of ordinary Portland cement A review of the

chemistry of both materials makes it apparent that a blend of

the two will enhance the concrete product and efficiently

utilize the properties of both

VADVANTAGES OF FLY ASH BASED PORTLAND

CEMENT

AFly Ash improves concrete workability and lowers waterdemand

Fly Ash particles are mostly spherical tiny glass beads

Ground materials such as Portland Cement are solid angular particles Fly Ash particles provide a greater workability of

the powder portion of the concrete mixture which results in

greater workability of the concrete and a lowering of waterrequirement for the same concrete consistency Pump ability

is greatly enhanced

BFly Ash generally exhibit less bleeding and segregation than plain concretes

This makes the use of Fly Ash particularity valuable in

concrete mixtures made with aggregates deficient in fines

CSulphate and Alkali Aggregate Resistance

Class F and a few Class C Fly Ashes impart significant

sulphate resistance and alkali aggregate reaction resistance tothe concrete mixture

DFly Ash has a lower heat of hydration

Portland cement produces considerable heat upon

hydration In mass concrete placements the excess internal

heat may contribute to cracking The use of Fly Ash may

greatly reduce this heat build up and reduce external cracking

FFly Ash generally reduces the permeability and adsorption

of concrete

By reducing the permeability of chloride ion corrosion of

embedded steel is greatly decreased Also chemical resistanceis improved by the reduction of permeability and adsorption



GFly Ash is economical

The cost of Fly Ash is generally less than Portland Cement

depending on transportation Significant quantities may be

substituted for Portland Cement in concrete mixtures and thusincrease the long term strength and durability Thus the use of

Fly Ash may impart considerable benefits to the concrete

mixture over a plain concrete for less cost

HIGH-VOLUME FLY ASH (HVFA) CONCRETE

Fly Ash has a vast potential for use in High Volume Fly

Ash (HVFA) concrete especially due to its physic-chemical

properties Considerable amount of research has already been

done in India and abroad on its strength and other requisite

parameters In commercial practice the dosage of fly ash is

limited to 15-20 by mass of the total cementitious

material Usually this amount has a beneficial effect on the

workability and cost economy of concrete but it may not be

enough to sufficiently improve the durability to sulphate

attack alkali-silica expansion and thermal cracking Thus

from theoretical considerations and practical experience it is

established that with 50 or more cement replacement by fly

ash it is possible to produce sustainable high performance

concrete mixtures that show high workability high ultimate

strength and high durability

ICHARACTERISTICS DEFINING HVFA CONCRETE

MIXTURE

The characteristics defining a HVFA concrete mixture are

as follows

1) Minimum of 50 of fly ash by mass of the cementitious

materials must be maintained

2) Low water content generally less than 130 kgm3 is

mandatory

3) Cement content generally no more than 200kgm3 is

desirable

4) For concrete mixtures with specified 28-day compressive

strength of 30 MPa or higher slumps greater than 150 mm

and water-to-cementitious materials ratio of the order of 030

the use of high range water-reducing admixtures

(superplasticizers) is mandatory

5) For concrete exposed to freezing and thawing

environments the use of an air-entraining admixture resulting

in adequate air-void spacing factor is mandatory

6) For concrete mixtures with slumps less than 150 mm and

28-day compressive strength of less than 30 MPa HVFA

concrete mixtures with a water-to-cementitious materials ratio

of the order of 040 may be used without superplasticizers

IIMECHANISMS BY WHICH FLY ASH IMPROVES THE

PROPERTY OF CONCRETE

A good understanding of the mechanisms by which fly ash

improves the rheological properties of fresh concrete and

ultimate strength as well as durability of hardened concrete is

helpful to insure that potential benefits expected from HVFA

concrete mixtures are fully realized These mechanisms are

discussed next

AFly ash as a water reducer

There are two reasons why typical concrete mixtures

contain too much mixing-water Typical concrete mixtures do

not have an optimum particle size distribution and this

accounts for the undesirably high water requirement to

achieve certain workability Secondly to plasticize a cement

paste for achieving a satisfactory consistency much larger

amounts of water than necessary for the hydration of cement

have to be used because portland cement particles due to the

presence of electric charge on the surface tend to form flocs

that trap volumes of the mixing water It is generally observed

that a partial substitution of portland cement by fly ash in a

mortar or concrete mixture reduces that water requirement for

obtaining a given consistency Experimental studies have

shown that with HVFA concrete mixtures depending on thequality of fly ash and the amount of cement replaced up to

20 reduction in water requirements can be achieved This

means that good fly ash can act as a superplasticizing

admixture when used in high-volume The phenomenon is

attributable to three mechanisms First fine particles of fly ash

get absorbed on the oppositely charged surfaces of cement

particles and prevent them from flocculation The cement

particles are thus effectively dispersed and will trap large

amounts of water that means that the system will have a

reduced water requirement to achieve a given consistency

Secondly the spherical shape and the smooth surface of flyash particles help to reduce the interparticle friction and thus

facilitates mobility Thirdly the ldquoparticle packing effectrdquo is

also responsible for the reduced water demand in plasticizing

the system It may be noted that both portland cement and fly

ash contribute particles that are mostly in the 1 to 45 983221m size

range and therefore serve as excellent fillers for the void

space within the aggregate mixture In fact due to its lower

density and higher volume per unit mass fly ash is a more

efficient void-filler than portland cement



BDrying shrinkage

Perhaps the greatest disadvantage associated with the use

of neat portland-cement concrete is cracking due to drying

shrinkage The drying shrinkage of concrete is directly

influenced by the amount and the quality of the cement paste

present It increases with an increase in the cement paste-to-

aggregate ratio in the concrete mixture and also increases

with the water content of the paste Clearly the water-

reducing property of fly ash can be advantageously used for

achieving a considerable reduction in the drying shrinkage of

concrete mixtures Table 2 shows mixture proportions of a

conventional 25 MPa concrete compared to a superplasticized

HVFA concrete with similar strength but higher slump Due to

a significant reduction in the water requirement the total

volume of the cement paste in the HVFA concrete is only

25 as compared to 296 for the conventional portland-

cement concrete which represents a 30 reduction in the

cement paste-to-aggregate volume ratio

TABLE 2

COMPARISION OF CEMENT PASTE VOLUMES

Conventional

concrete

HVFA

concrete

kgm3 m

3 kgm

3 m

3

Cement 307 0098 154 0149

Fly ash - - 154 0065

Water 178 0178 120 0120

Entrapped air

(2)

- 0020 - 0020

Course aggregate 1040 0385 1210 0448

Fine aggregate 825 0305 775 0287

Total 2350 0986 2413 0989

wcm 058 - 039 -

Paste volume - 0296 - 0254

Paste percent - 300 - 257

CThermal cracking

Thermal cracking is of serious concern in massive concrete

and reinforced concrete structures For unreinforced mass-

concrete construction several methods are employed to

prevent thermal cracking and some of these techniques can be

successfully used for mitigation of thermal cracks in massive

reinforced-concrete structures For instance a 40-MPa

concrete mixture containing 350 kgm3 portland cement can

raise the temperature of concrete by approximately 55-60oC

within a week if there is no heat loss to the environment

However with a HVFA concrete mixture containing 50

cement replacement with a Class F fly ash the adiabatic

temperature rise is expected to be 30-35oC

DWater-tightness and durability

In general the resistance of a reinforced-concrete structure

to corrosion alkali aggregate expansion sulphate and other

forms of chemical attack depends on the water-tightness of theconcrete The water-tightness is greatly influenced by the

amount of mixing-water type and amount of supplementary

cementing materials curing and cracking resistance of

concrete High-volume fly ash concrete mixtures when

properly cured are able to provide excellent water-tightness

and durability The mechanisms responsible for this

phenomenon are discussed briefly below

When a concrete mixture is consolidated after placement

along with entrapped air a part of the mixing-water is also

released As water has low density it tends to travel to the

surface of concrete However not all of this ldquobleed waterrdquo is

able to find its way to the surface Due to the wall effect of

coarse aggregate particles some of it accumulates in the

vicinity of aggregate surfaces causing a heterogeneous

distribution of water in the system Obviously the interfacial

transition zone between the aggregate and cement paste is the

area with high watercement and therefore with more available

space that permits the formation of a highly porous hydration

product containing large crystals of calcium hydroxide and

ettringite Microcracks due to stress are readily formed

through this product because it is much weaker than the bulk

cement paste with a lower watercement It has been suggested

that microcracks in the interfacial transition zone play an

important part in determining not only the mechanical

properties but also the permeability and durability of concrete

exposed to severe environmental conditions This is because

the rate of fluid transport in concrete is much larger by

percolation through an interconnected network of microcracks

than by diffusion or capillary suction The heterogeneities in

the microstructure of the hydrated portland-cement paste

especially the existence of large pores and large crystalline

products in the transition zone are greatly reduced by the

introduction of fine particles of fly ash With the progress ofthe pozzolanic reaction a gradual decrease occurs in both the

size of the capillary pores and the crystalline hydration

products in the transition zone thereby reducing its thickness

and eliminating the weak link in the concrete microstructure

In conclusion a combination of particle packing effect low

water content and pozzolanic reaction accounts for the

eventual disappearance of the interfacial transition zone in

HVFA concrete and thus enables the development of a highly

crack-resistant and durable product



IIIPROPERTIES OF HVFA CONCRETE

Based on field experience and laboratory tests the

properties of HVFA concrete when compared to conventional

portland cement concrete can be summarized as follows

1) Easier flowability pumpability and compactability

2) Better surface finish and quicker finishing time when

power finish is not required

3) Slower setting time which will have a corresponding effect

on the joint cutting and lower power-finishing times for slabs

4) Early-strength up to 7 days which can be accelerated with

suitable changes in the mix design when earlier removal of

formwork or early structural loading is desired

5) Much later strength gain between 28 days and 90 days or

more (With HVFA concrete mixtures the strengthenhancement between 7 and 90-day often exceeds 100

therefore it is unnecessary to over design them with respect to

a given specified strength)

6) Superior dimensional stability and resistance to cracking

from thermal shrinkage autogenous shrinkage and drying

shrinkage

7) After three to six months of curing much higher electrical

resistivity and resistance to chloride ion penetration

according to ASTM Method C1202

8) Very high durability to the reinforcement corrosion alkali-

silica expansion and sulphate attack

9) Better cost economy due to lower material cost and highly

favorable lifecycle cost

10) Superior environmental friendliness due to ecological

disposal of large quantities of fly ash reduced carbon-dioxide

emissions and enhancement of resource productivity of the

concrete construction industry

CONCLUSION

The study of Fly Ash has shown that owing to its numerous

advantageous physical and chemical properties the material is

found to be one of the best admixtures in Portland cement

concrete and High Volume Fly Ash (HVFA) concrete making

which improves not only the quality but also its workability

subjected to various parameters Moreover the fly ash

concrete offers a holistic solution to the problem of fly ash

disposal which is one of the major issues now-a-days that too

in a sustainable manner at a reduced or no additional cost and

at the same time reducing the environmental impact of two

industries that are vital to economic development namely the

cement industry and the coal-fired power industry Thus it

also favours the Green Technology and waste management

which in turn helps in sustainable development

ACKNOWLEDGMENT

I wish to acknowledge the instructive guidance of Prof

RB Bajare Asst Professor and Prof Dr S R Parekar

HOD Dept of Civil Engineering Sinhgad Academy of

Engineering

REFERENCES

[1] Parisara ENVIS Newsletter (Vol2 No 6 January 2007) by State

Environment Related Issues Department of Forests Ecology and

Environment Government of Karnataka

[2 ] High Volume Fly-Ash Concrete Technology Fly Ash Summary Report in

India by Canadian International Development Agency (CIDA)

[3] P Kumar Mehta HIGH-PERFORMANCE HIGH-VOLUME FLY ASH

CONCRETE FOR SUSTAINABLE DEVELOPMENT International

Workshop on Sustainable Development and Concrete Technology University

of California Berkeley USA

[4] httpwwwashgroveresourcescom

[5] Fly ash From Wikipedia the free encyclopedia

[6] C N Jha amp J K Prasad ldquoFLY ASH A RESOURCE MATERIAL FOR

INNOVATIVE BUILDING MATERIAL - INDIAN PERSPECTIVErdquo

[7] Headwaters Resources Chemical Comparison of Fly Ash and Portland

Cement Bulletin No 2



ash utilization within 3 years Presently out of 110 million

tonnes of total ash generated only about 30 is being

utilized Therefore thermal power stations are under great

pressure to find useful applications of fly ash The technology

utilizing fly ash in high volume fly ash concrete can provide

an avenue for utilization of fly ash on a bulk scale

VI PROBLEMS DUE TO FLY ASH

Fly ash is a very fine powder and tends to travel far in the

air When not properly disposed it is known to pollute air andwater and causes respiratory problems when inhaled When it

settles on leaves and crops in fields around the power plant it

lowers the yield The conventional method used for disposal

of both fly ash and bottom ash is to convert them into slurry

for impounding in ash ponds around the thermal plants Thismethod entails long-term problems The severe problems that

arise from such dumping are

1) The construction of ash ponds requires vast tracts of land

This depletes land available for agriculture over a period of

time

2) When one ash pond fills up another has to be built at great

cost and further loss of agricultural land

3) Huge quantities of water are required to convert ash into

slurry During rains numerous salts and metallic content inthe slurry can leach down to the groundwater and contaminate

it

Taking into account these facts fly ash is being used in

various construction activities as a raw material In this paper

detailed study of use of fly ash in raw materials like Portland

cement is considered Further this paper reviews the use of

high volume fly ash in cement making for better yield

FLY ASH BASED POZZOLANA PORTLAND

CEMENT

IPOZZOLANS

Pozzolans are defined as silicious and aluminous materials

which in themselves possess little or no cementitious value

but in finely divided form and in the presence of moisture it

chemically react with calcium hydroxide at ordinary

temperature to form compounds possessing cementitious

properties

IICLASS F FLY ASH

The burning of harder older anthracite and bituminous

coal typically produces Class F fly ash This fly ash is

pozzolanic in nature and contains less than 20 lime (CaO)

Possessing pozzolanic properties the glassy silica and

alumina of Class F fly ash requires a cementing agent such

Portland cement quicklime or hydrated lime with the

presence of water in order to react and produce cementitious

compounds

Most of the state and federal specifications allow and even

encourage the use of Fly Ash especially when specificdurability requirements are needed Fly Ash has a long history

of use in concrete Fly Ash is used in about 50 of ready

mixed concrete Class C Fly Ash is used at dosages of 15 to40 by mass of the cementitious materials in the concrete

Class F is generally used at dosages of 15 to 30

IIIFLY ASH IN PORTLAND CEMENT

Owing to its pozzolanic properties fly ash is used as a

replacement for some of the Portland cement content of

concrete The use of fly ash as a pozzolanic ingredient was

recognized as early as 1914 although the earliest noteworthystudy of its use was in 1937Before its use was lost to the Dark

Ages Roman structures such as aqueducts or the Pantheon in

Rome used volcanic ash (which possesses similar properties to

fly ash) as pozzolan in their concrete As pozzolan greatly

improves the strength and durability of concrete the use of

ash is a key factor in their preservation

Use of fly ash as a partial replacement for Portland cement

is generally limited to Class F fly ashes It can replace up to

30 by mass of Portland cement and can add to the final

strength of concrete and increase its chemical resistance and

durability Recently concrete mix design for partial cement

replacement with High Volume Fly Ash (50 cement

replacement) has been developed For Roller Compacted

Concrete (RCC) [used in dam construction] replacement

values of 70 have been achieved with processed fly ash at

the Ghatghar Dam project in Maharashtra India Due to the

spherical shape of fly ash particles it can also increase

workability of cement while reducing water demand The

replacement of Portland cement with fly ash is considered by

its promoters to reduce the greenhouse gas footprint of

concrete as the production of one ton of Portland cement

produces approximately one ton of CO2 as compared to zeroCO2 being produced using existing fly ash New fly ash

production ie the burning of coal produces approximately

twenty to thirty tons of CO2 per ton of fly ash Since the

worldwide production of Portland cement is expected to reach

nearly 2 billion tons by 2012 replacement of any large portion

of this cement by fly ash can significantly reduce carbon

emissions associated with construction














PORTLAND CEMENT


of portland cement

TABLE I



Chemical

compound


SiO 5490 260

Al2O3 2580 430

Fe2O3 690 240

CaO 870 6440

MgO 180 210

SO2 060 230

Na2O amp K 2O 060 060



table reveals








has smaller amounts


Free Lime (CaOH)














CEMENT






is greatly enhanced













of concrete




























MIXTURE


as follows




mandatory


desirable




















discussed next




































BDrying shrinkage


















TABLE 2


Conventional

concrete

HVFA

concrete

kgm3 m

3 kgm

3 m

3

Cement 307 0098 154 0149

Fly ash - - 154 0065

Water 178 0178 120 0120

Entrapped air

(2)

- 0020 - 0020



Total 2350 0986 2413 0989

wcm 058 - 039 -



CThermal cracking













































































shrinkage












CONCLUSION















ACKNOWLEDGMENT




Engineering

REFERENCES





























PORTLAND CEMENT


of portland cement

TABLE I



Chemical

compound


SiO 5490 260

Al2O3 2580 430

Fe2O3 690 240

CaO 870 6440

MgO 180 210

SO2 060 230

Na2O amp K 2O 060 060



table reveals








has smaller amounts


Free Lime (CaOH)














CEMENT






is greatly enhanced













of concrete




























MIXTURE


as follows




mandatory


desirable




















discussed next




































BDrying shrinkage


















TABLE 2


Conventional

concrete

HVFA

concrete

kgm3 m

3 kgm

3 m

3

Cement 307 0098 154 0149

Fly ash - - 154 0065

Water 178 0178 120 0120

Entrapped air

(2)

- 0020 - 0020



Total 2350 0986 2413 0989

wcm 058 - 039 -



CThermal cracking













































































shrinkage












CONCLUSION















ACKNOWLEDGMENT




Engineering

REFERENCES









































MIXTURE


as follows




mandatory


desirable




















discussed next




































BDrying shrinkage


















TABLE 2


Conventional

concrete

HVFA

concrete

kgm3 m

3 kgm

3 m

3

Cement 307 0098 154 0149

Fly ash - - 154 0065

Water 178 0178 120 0120

Entrapped air

(2)

- 0020 - 0020



Total 2350 0986 2413 0989

wcm 058 - 039 -



CThermal cracking













































































shrinkage












CONCLUSION















ACKNOWLEDGMENT




Engineering

REFERENCES


















BDrying shrinkage


















TABLE 2


Conventional

concrete

HVFA

concrete

kgm3 m

3 kgm

3 m

3

Cement 307 0098 154 0149

Fly ash - - 154 0065

Water 178 0178 120 0120

Entrapped air

(2)

- 0020 - 0020



Total 2350 0986 2413 0989

wcm 058 - 039 -



CThermal cracking













































































shrinkage












CONCLUSION















ACKNOWLEDGMENT




Engineering

REFERENCES




































shrinkage












CONCLUSION















ACKNOWLEDGMENT




Engineering

REFERENCES
















Documents

Utilisation of Fly Ash in Cement Concrete