Fly Ash Ppt - Copy

Tuesday, April 11, 2023FLY ASH IN CONCRETE

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Fly Ash In Concrete

By-

Anupam Agrawal &

Devdutta Vajpayee

L.N.C.T. BHOPAL

Tuesday, April 11, 2023 FLY ASH IN CONCRETE 2

Content-Introduction of Fly Ash

History

Classification

Uses of Fly Ash

High Volume Fly Ash Concrete

Present Scenario

Contribution towards Environment


What is Fly Ash? Fly ash is one of the residues generated in the

combustion of coal. Fly ash is generally captured from the chimneys of coal-fired power plants.

Chemically, fly ash is a pozzolan. When mixed with lime (calcium hydroxide), pozzolans combine to form cementitious compounds.

http://en.wikipedia.org/wiki/Combustion

http://en.wikipedia.org/wiki/Coal

http://en.wikipedia.org/wiki/Fossil_fuel_power_plant


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FLY ASH

(Courtesy of U. of Québec)


More than 2000 years ago, Greeks and Romans built structures that survive today that took advantage of the pozzolan-lime reaction.

Romans used pozzolana cement to build the Appian Way, The Roman baths, The Coliseum and Pantheon in Rome. These structures still exist today!

History-


Classification-

Class F fly ash:

Fly ash that is produced from the burning of anthracite or bituminous coal is referred as Class F fly ash.

Class C fly ash.

Fly ash that is produced from the burning of lignite or sub bituminous coal is referred as Class C fly ash. Most Class C fly ashes have self-cementing properties.


Uses of Fly ash

Used in cementFly Ash blended cement

(PPC) too is gaining acceptance. The share of Ordinary Portland Cement is projected to decline to 57.9% from 71% by the year 2011.

Used in concrete.

In concrete it is used normally as main ingredient.

Usage ranges from 15% to 60%.

e.g.-high volume fly ash concrete (HVFAC)


Fly Ash Checklist-

Fresh Concrete

Enhancing concrete workability

Ease of Pumping

Improved Finishing

Reduced Bleeding

Reduced Segregation

Hardened Concrete

Increasing Concrete Performance

Higher Strength

Decreased Permeability

Increased Durability

Reduced Sulfate Attack

Reduced Heat of Hydration


First usage of fly ash concrete.

HUNGRY HORSE DAM

In 1929,U.S.A.


1st Usage In India

RIHAND IRRIGATION PROJECT, UP (1962)


High Volume Fly Ash Concrete.

50% to 60% fly ash is incorporated.

Low Water Content.

Low Heat of Hydration.

Low Cement Content.

produce sustainable, high performance concrete mixtures that show high workability, high ultimate strength, and high durability.


Properties of HVFA ConcreteEasier flowability, pumpability, and compactability

Slower setting time

Early-strength up to 7 days, which can be accelerated with suitable changes in the mix design

Much later strength gain between 28 days and 90 days or more


Superior dimensional stability and resistance to cracking.

After 3 to 6 months of curing, much higher electrical resistivity.

Very high durability to the reinforcement corrosion.

Better cost economy due to lower material cost and highly favorable lifecycle Cost.

Superior environmental friendliness due to ecological disposal of large quantities of fly ash.


Product ComparisonsHigh Volume Fly Ash

Concrete

• Less energy intensive manufacture

• Higher ultimate strength

• More durable

• Uses a waste by-product

• Less global warming gases created

• Is a LEED certified material

Conventional Concrete

• Energy intensive manufacturing

• Weaker ultimate strength

• Less durable

• Uses virgin material

• More global warming gases created


HVFA Concrete Used-

1999 GAP Headquarters Building, San Francisco, CA

50% fly ash concrete in pile caps and slab-on- grade work; 30% used incolumn and slab-on- metal deck work

2000 Island Wood Environmental Learning CenterWhidbey Island, WA

50% fly ash concrete in footings,stem-walls, and slab-on-grade

2001 University of California Berkeley, CA

50% fly ash concrete used in Wurster Hall and Barker Hall seismic retrofits


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Wurster Hall,Berkeley, CA


Why Fly Ash is Ideal for the Interstate Highway System and Secondary Roads ?

HVFA is more durable than asphaltic concrete and needs almost no maintenance.

The design of a highway pavement is based on flexural strength and HVFA concrete keeps gaining strength with age .

There is no reinforcing steel in pavement concrete and roller compacted concrete. Thus the corrosion of steel is a non issues.

It increases fuel efficiency of transport trucks by 11%, resulting in cost savings and lower exhaust emissions..

HVFA concrete is competitive with asphaltic concrete even onfirst-cost basis


Chemical Interaction of Fly Ash with Concrete-Making Materials

When Portland cement hydrates, calcium hydroxide is formed.

Approximately 20% of the weight of Portland cement is converted to calcium hydroxide

• Does not strengthen concrete.

Calcium hydroxide is soluble in water and may be removed by leaching action.

When fly ash is employed, hydrated lime combines with fly ash to form a stable cementitious compound.

• Helps strengthen concrete.


Fly Ash Availability and PortlandCement Production in India in2002-2010

Fly ash availability:

Estimated availability 2002: 80 to 100 million tonnes

Estimated availability in 2010: 180 to 200 million tonnes

Portland cement production:

Estimated availability in 2002: 80 million tonnes

Estimated availability in 2010: 120 million tonnes


Present Scenario

Indian RMC Manufacturers add 15-18% fly ash to concrete but the common man here still does not comprehend the benefits derived from the usage of fly ash in cement or in concrete.

In the US, the State of Wisconsin has been using a 60% Class F fly ash in concrete mix since 1989.

The Park lane Development in Halifax, Canada is a seven story structure and was built with 55% high-volume fly ash concrete .


World Cement Productionto Year 2010

s.no Year World total (million tonnes)

1 1995 1,396

2 2000 1,662

3 2005 1,839

4 2010 1,946


World-wide Cement Productionand CO2 Emissions

S.no. year CementProduction,billiontonnes

Total CO2Emissions,billiontonnes

CO2Contributionby cementIndustry, %

1 1995 1.4 21.6 7

2 2000 1.9 28-30 7


Reduction of CO2 Emissions byIncreased use of Fly Ash-

Replacing 15% of cement worldwide by SCM will reduce CO2 emissions by 227 million tonnes.

Replacing 50% of cement worldwide by SCM will reduce CO2 emissions by 750 million tonnes. This is equal to removing 1/4of all automobiles in the world.


Uses of Fly Ash In India Interstate highway system (both for the

pavement and the base course)

Secondary roads using roller-compacted concrete

Low-cost subsidized housing

Structural concrete for buildings

Development of added value products by beneficiating fly ash to replace imported silica fume


Just 1 ton of fly ash use equals-

Conserved Landfill Space

Enough for 455 days of solid waste produced by an average man.

Reduced CO2 Emissions

Equal to two months of emissions from an automobile.

Saved Energy Enough to provide electricity to an average home for 24 days.


Health Attributes

There are traces of heavy metals in the fly ash.

Some debate that the metals are effectively locked into the cement matrix, preventing their release.

By using fly ash in concrete rather than “landfilling” it, the potential for the metals to leach into the environment is reduced.

Concerns have also been raised about the higher incidence of Radium-226 in fly ash


Alternative Resources

Rice husk ash, created by the controlled burning of an agricultural waste product, can be added to mixes to further increase the strength and reduce the permeability of fly ash concrete.

Tuesday, April 11, 2023FLY ASH IN CONCRETE

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Portland Cement is environmentally very unfriendly material.

As good engineers, we must reduce its use in concrete.


So what is the solution ?

As good engineers, we must use more environmentally friendly Supplementary Cementing Materials in concrete. These materials are :

Fly Ash

Granulated B.F. Slag

Silica Fume

Rice-husk Ash


Questions…?


“ Thank You ”

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Fly Ash Ppt - Copy