Ppt

A SEMINAR REPORT ONA SEMINAR REPORT ON

““EFFECT OF FLY ASH AND SILICA FUMEEFFECT OF FLY ASH AND SILICA FUMEON CONCRETE”ON CONCRETE”

UNDER THE GUIDANCE OFUNDER THE GUIDANCE OF

Prof. A.M.GalagaliProf. A.M.Galagali

SUBMITTED BYSUBMITTED BYMohammad Ali. A. JamadarMohammad Ali. A. Jamadar

US No: 2BV05CV401US No: 2BV05CV401

SEQUENCE OF SLIDESSEQUENCE OF SLIDES

1.0 Introduction1.0 Introduction

2.02.0 Materials Materials 2.1. Fly ash 2.1. Fly ash 2.2 Silica fume2.2 Silica fume

3.0 Effect of fly ash on concrete3.0 Effect of fly ash on concrete 3.1. Influence of fly ash on property of fresh concrete3.1. Influence of fly ash on property of fresh concrete

3.2. Strength development of fly as concrete3.2. Strength development of fly as concrete 3.3. Durability aspect3.3. Durability aspect

4.0 Effect of silica fume on concrete4.0 Effect of silica fume on concrete 4.1. Influence of silica fume on property of fresh concrete4.1. Influence of silica fume on property of fresh concrete 4.2 Strength development of the Portland cement-silica system 4.2 Strength development of the Portland cement-silica system 4.3 Durability of concrete congaing silica fume4.3 Durability of concrete congaing silica fume

5.0 Conclusion5.0 Conclusion

6.06.0 References References

INTRODUCTIONINTRODUCTION

Earlier notion of using high amounts of cement for Earlier notion of using high amounts of cement for concrete has now changed on favour of increased use of high concrete has now changed on favour of increased use of high amounts of mineral ad-mixtures and super plasticizers with amounts of mineral ad-mixtures and super plasticizers with reduced amounts of cement and water in the concrete mixtures. reduced amounts of cement and water in the concrete mixtures. Energy plays a crucial role in growth of developing countries, like Energy plays a crucial role in growth of developing countries, like India.India.

MATERIALSMATERIALS

Fly AshFly Ash&&

Silica FumeSilica Fume

FLYASH (PULVERIZED-FUEL ASH)FLYASH (PULVERIZED-FUEL ASH) Fly ash is a by-product of burning pulverized coal to generate electric power. Fly ash is a by-product of burning pulverized coal to generate electric power.

The fly ash particles are spherical.The fly ash particles are spherical.

Fly ash has very high fineness with Specific Surface of between 250 to 600mFly ash has very high fineness with Specific Surface of between 250 to 600m22/kg./kg.

Specific gravity is around 2.35.Specific gravity is around 2.35.

There are two classes of fly ash. There are two classes of fly ash.

One is Class F fly ash which is obtained from the burning of bituminous coal, usually has less One is Class F fly ash which is obtained from the burning of bituminous coal, usually has less than 5% CaOthan 5% CaO

Second is Class C fly ash which is obtained from burning of lignite. It may have CaO content Second is Class C fly ash which is obtained from burning of lignite. It may have CaO content is excess of 10%. is excess of 10%.

SILICA FUME (SILICA FUME (MicrosilicaMicrosilica))

Silica fume is a by-product of silicon or Ferro-Silica industry and is Silica fume is a by-product of silicon or Ferro-Silica industry and is 100 times finer than cement. 100 times finer than cement.

The specific gravity of silica fumes is generally 2.20.The specific gravity of silica fumes is generally 2.20.

The particles of silica fume are extremely fine, most of them The particles of silica fume are extremely fine, most of them having a diameter ranging between 0.03 and 0.3having a diameter ranging between 0.03 and 0.3m.m.

Specific surface of about 20000mSpecific surface of about 20000m22/kg, which is 13 to 20 times /kg, which is 13 to 20 times higher than the specific surface of other pozzolanic materials.higher than the specific surface of other pozzolanic materials.

Such fine material as silica fume has a very low bulk density: 200 Such fine material as silica fume has a very low bulk density: 200 to 300kg/mto 300kg/m33..

EFFECT OF FLY ASH ON CONCRETEEFFECT OF FLY ASH ON CONCRETE

INFLUENCE OF FLY ASH ON PROPERTIES OF FRESH INFLUENCE OF FLY ASH ON PROPERTIES OF FRESH CONCRETECONCRETE

Concrete WorkabilityConcrete Workability:: Use of fly ash increases the absolute volume of cementitious Use of fly ash increases the absolute volume of cementitious

materials (cement plus fly ash) compared to non-fly-ash concrete; materials (cement plus fly ash) compared to non-fly-ash concrete; therefore, the paste volume is increased, leading to a reduction in therefore, the paste volume is increased, leading to a reduction in aggregate particle interference and enhancement in concrete aggregate particle interference and enhancement in concrete workability. workability.

The spherical particle shape of fly ash also participates in improving The spherical particle shape of fly ash also participates in improving workability of fly ash concrete because of the so-called "ball workability of fly ash concrete because of the so-called "ball bearing" bearing"

Water demand:Water demand: For a constant workability, the reduction in the water demand of For a constant workability, the reduction in the water demand of

concrete due to fly ash is usually between 5 and 15 percent by concrete due to fly ash is usually between 5 and 15 percent by comparison with a Portland –cement –only mix having the same comparison with a Portland –cement –only mix having the same cementations material content; the reduction is larger at higher cementations material content; the reduction is larger at higher water/cement ratio.water/cement ratio.

Bleeding:Bleeding: A concrete mix containing fly ash is cohesive and has reduced bleeding A concrete mix containing fly ash is cohesive and has reduced bleeding

capacity. The mix can be suitable for pumping and for slip forming; finishing capacity. The mix can be suitable for pumping and for slip forming; finishing operations of fly ash concrete and made easier.operations of fly ash concrete and made easier.

Concrete with relatively high fly ash content will require less water than non-Concrete with relatively high fly ash content will require less water than non-fly-ash concrete of equal slump fly-ash concrete of equal slump

Time of Setting:Time of Setting: All Class F and most Class C fly ashes increase the time of setting of concrete.All Class F and most Class C fly ashes increase the time of setting of concrete.

Time of setting of fly ash concrete is influenced by the characteristics and Time of setting of fly ash concrete is influenced by the characteristics and amounts of fly ash used in concrete. amounts of fly ash used in concrete.

STRENGTH DEVELOPMENT OF FLY ASH CONCRETESTRENGTH DEVELOPMENT OF FLY ASH CONCRETE

Packing:Packing: Extent of packing depends both on the fly ash and cement used. Better Extent of packing depends both on the fly ash and cement used. Better

packing is achieved with coarser Portland cement with finer fly ash.packing is achieved with coarser Portland cement with finer fly ash.

Due to packing there will reduction in the entrapped air in concrete and Due to packing there will reduction in the entrapped air in concrete and volume of large capillary pores also reduces.volume of large capillary pores also reduces.

Density of concrete:Density of concrete: Density of concrete is increase which is beneficial with respect to strength, Density of concrete is increase which is beneficial with respect to strength,

resistance to crack and stiffness.resistance to crack and stiffness.

Compressive Strength:Compressive Strength:

Due to continued pozzonic reactivity concrete develops greater Due to continued pozzonic reactivity concrete develops greater strength at later age, which may exceed that of concrete without strength at later age, which may exceed that of concrete without fly ash.fly ash.

Permeability of concretePermeability of concrete::

The pozzonic reaction also contributes to making the texture of The pozzonic reaction also contributes to making the texture of concrete dense, resulting in decrease of water permeability and concrete dense, resulting in decrease of water permeability and gas permeability.gas permeability.

DURABILITY ASPECTSDURABILITY ASPECTS

Sulfate attack:Sulfate attack: Alumina and lime in the fly ash may contribute to the sulfate Alumina and lime in the fly ash may contribute to the sulfate

reactions. A high silica/alumina ratio probably reduces the reactions. A high silica/alumina ratio probably reduces the vulnerability to sulfate attack but no reliable generalization is vulnerability to sulfate attack but no reliable generalization is possible.possible.

Freeze-thawing:Freeze-thawing: Fly ash has not adverse effect on the resistance to freezing Fly ash has not adverse effect on the resistance to freezing

and thawing of air entrained concrete.and thawing of air entrained concrete.

Carbon:Carbon:

It has been found that high-carbon-content fly ash reduces It has been found that high-carbon-content fly ash reduces the effectiveness of admixtures such as air-entraining agents the effectiveness of admixtures such as air-entraining agents

Alkali-silica Reaction:Alkali-silica Reaction: The alkalies released by the cement preferentially combine with The alkalies released by the cement preferentially combine with

the reactive silica in the fly ash rather than in the aggregate.the reactive silica in the fly ash rather than in the aggregate.

The alkalies are tied up in nonexpansive calcium-alkali-silica gel. The alkalies are tied up in nonexpansive calcium-alkali-silica gel. Thus hydroxyl ions remaining in the solution are insufficient to Thus hydroxyl ions remaining in the solution are insufficient to react with the material in the interior of the larger reactive react with the material in the interior of the larger reactive aggregate particles and disruptive osmotic forces are not aggregate particles and disruptive osmotic forces are not generated.generated.

Chloride:Chloride: Due to reduced permeability of mature concrete containing fly ash Due to reduced permeability of mature concrete containing fly ash

the chloride ingress into such concrete is reduced.the chloride ingress into such concrete is reduced.

EFFECT OF SILICA FUME ON CONCRETEEFFECT OF SILICA FUME ON CONCRETE

INFLUENCE OF SILICA FUME ON PROPERTIES OF RESH INFLUENCE OF SILICA FUME ON PROPERTIES OF RESH CONCRETECONCRETE

Effects on Water Requirements of Fresh Concrete:Effects on Water Requirements of Fresh Concrete: The demand of water will be increased due to very large surface The demand of water will be increased due to very large surface

area of the particles of silica fume so that, in mixes with a low area of the particles of silica fume so that, in mixes with a low water/cement ratio, it necessary to use a superplasticizer. In this water/cement ratio, it necessary to use a superplasticizer. In this way, it is possible to maintain both the required water/cement way, it is possible to maintain both the required water/cement ratio and the necessary workability.ratio and the necessary workability.

Effects on Consistency and Bleeding of Fresh Concrete:Effects on Consistency and Bleeding of Fresh Concrete: Concrete incorporating more than 10% Silica Fume becomes Concrete incorporating more than 10% Silica Fume becomes

sticky; in order to enhance workability, the initial slump should be sticky; in order to enhance workability, the initial slump should be increased. It has been found that Silica Fume reduces bleeding.increased. It has been found that Silica Fume reduces bleeding.

The reduced bleeding can lead to plastic shrinkage cracking under The reduced bleeding can lead to plastic shrinkage cracking under

drying conditions, unless preventive measures are taken. drying conditions, unless preventive measures are taken.

STRENGTH DEVELOPMENT OF SILICA FUMESTRENGTH DEVELOPMENT OF SILICA FUME CONCRETCONCRET

Early StrengthEarly Strength The early strength development is probably through improvement The early strength development is probably through improvement

in packing that is action as a filler and improvement of the in packing that is action as a filler and improvement of the interface zone with aggregate.interface zone with aggregate.High Strength ConcreteHigh Strength Concrete::

Silica Fume has been successfully used to produce very high-Silica Fume has been successfully used to produce very high-strength, low-permeability, and chemically resistant concrete. strength, low-permeability, and chemically resistant concrete. Addition of Silica Fume by itself, with other factors being constant, Addition of Silica Fume by itself, with other factors being constant, increases the concrete strength.increases the concrete strength.Modulus of Elasticity:Modulus of Elasticity:

The modulus of elasticity of concrete containing silica fume is The modulus of elasticity of concrete containing silica fume is somewhat higher than is the case with Portland cement only somewhat higher than is the case with Portland cement only concretes of similar strength it has been reported that concrete concretes of similar strength it has been reported that concrete containing silica fume is more brittle.containing silica fume is more brittle.Modulus of Rupture:Modulus of Rupture:

The modulus of rupture of Silica Fume concrete is usually either The modulus of rupture of Silica Fume concrete is usually either about the same as or somewhat higher than that of conventional about the same as or somewhat higher than that of conventional concrete at the same level of compressive strengthconcrete at the same level of compressive strength..Permeability of concrete:Permeability of concrete:

The permeability of concrete is also reducesThe permeability of concrete is also reduces..

DURABILITY OF CONCRETE CONTAINING DURABILITY OF CONCRETE CONTAINING SILICA FUMESILICA FUME

Chloride:Chloride: Reduced permeability is a greater resistance to the ingress of Reduced permeability is a greater resistance to the ingress of

chloride ions.chloride ions.

Sulfate Resistance:Sulfate Resistance: The sulfate resistance of concrete containing silica fume is good, The sulfate resistance of concrete containing silica fume is good,

partly because of a lower permeability and partly in consequence partly because of a lower permeability and partly in consequence of a lower content of calcium hydroxide and of alumina.of a lower content of calcium hydroxide and of alumina.

Freeze-Thawing:Freeze-Thawing: Use of Silica Fume has no significant influence on the production Use of Silica Fume has no significant influence on the production

and stability of the air-void system. Freeze-thaw testing on Silica and stability of the air-void system. Freeze-thaw testing on Silica Fume concrete showed acceptable results; the average durability Fume concrete showed acceptable results; the average durability factor was greater than 99%.factor was greater than 99%.

Abrasion Resistance:Abrasion Resistance: Due to absence of bleeding, no weak top layer is formed and also Due to absence of bleeding, no weak top layer is formed and also

because of a better bond between the hydrated cement paste and because of a better bond between the hydrated cement paste and coarse aggregate.coarse aggregate.

CONCLUSION:CONCLUSION:

Fly Ash:Fly Ash: It can replace up to 30% by mass of Portland cement, and It can replace up to 30% by mass of Portland cement, and

can add to the concrete’s final strength and increase its can add to the concrete’s final strength and increase its

chemical resistance and durability.chemical resistance and durability. Due to the spherical shape of fly ash particles, it can also Due to the spherical shape of fly ash particles, it can also

increase workability of cement while reducing water increase workability of cement while reducing water demand.demand.

The replacement of Portland cement with fly ash also The replacement of Portland cement with fly ash also reduces the greenhouse gas.reduces the greenhouse gas.

• Silica Fume:Silica Fume: silica fume improves compressive strength,bond strength, silica fume improves compressive strength,bond strength,

and abrasion resistance.and abrasion resistance. silica fume also reduces the permeability of concrete to silica fume also reduces the permeability of concrete to

chloride ions, which protects concrete's reinfrocing steel chloride ions, which protects concrete's reinfrocing steel from corrosion, especially in chloride-rich environments from corrosion, especially in chloride-rich environments such as those of roadways,runways and saltwater bridges.such as those of roadways,runways and saltwater bridges.

REFERENCESREFERENCES

1. A.M Neville, 1. A.M Neville, “Properties of Concrete”“Properties of Concrete”

Fourth and Final Edition, PEARSON EDUCATION,2005.Fourth and Final Edition, PEARSON EDUCATION,2005.

BIBLIOGRAPHYBIBLIOGRAPHY

1. M.S.Shetty, 1. M.S.Shetty, ”concrete technology” Theory and Practice, ”concrete technology” Theory and Practice, Rajendra Ravindra(Pvt)Ltd,2006.Rajendra Ravindra(Pvt)Ltd,2006.

2. 2. http://www.wikipedia.orghttp://www.wikipedia.org

3. http://www.fhwa.dot.gov/infrastructure/3. http://www.fhwa.dot.gov/infrastructure/

materialsgrp/silica.htmmaterialsgrp/silica.htm

4. http://www.dot.gov/infrastructure/materialsgrp/4. http://www.dot.gov/infrastructure/materialsgrp/

flyash.htmflyash.htm

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