LIGHT WEIGHT CONCRETE

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A Technical Seminar

On

By:

Hemanth K.R Hemanth K.R

Under the Guidelines:

Prof & Head Dept of

Prof & Head Dept of Civil Engg.Civil Engg.

Light Weight Concrete

Dr.K.P.Shivananda

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•

CONCRETE IS NOTHING BUT MIXTURE

OF AGGREGATES AND BINDER,

WHICH IS USED BY MAN FROM

THOUSANDS OF YEARS.

•

THE PEOPLE STARTED THINKING

ABOUT MAKING STRUCTURE LIGHT.

•

Let's TAKE A LOOK ON RESULT OF

THEIR THINKINGS………..

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HISTORY

•

• Romans appeared to have used Light weightRomans appeared to have used Light weight

Concrete in 2nd century, in the construction of

44m dia dome of Pantheon

44m dia dome of Pantheon •

• The search for artificial aggregates began in theThe search for artificial aggregates began in the beginning of 20th century.

beginning of 20th century. •

• In 1907, Ottoman [Hungarian] developed aIn 1907, Ottoman [Hungarian] developed a method of converting Blast furnace

method of converting Blast furnace slag in toslag in to

foamed structure, which is the first milestone of

Light Weight Concrete.

Light Weight Concrete. •

• The first commercial scale production of lightThe first commercial scale production of light weight aggregate manufactured in Kanas city,

weight aggregate manufactured in Kanas city,

in 1917, named as “HAYDITE”. in 1917, named as “HAYDITE”.

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•

• Other expanded clay aggregates such asOther expanded clay aggregates such as

“GRUELITE” “TERLITE” “ROCKLITE” were

“GRUELITE” “TERLITE” “ROCKLITE” were marketed by various American firms

marketed by various American firms

•

• In 1930, hollow globular burnt clay particlesIn 1930, hollow globular burnt clay particles known as globulite developed

known as globulite developed in Germany.in Germany.

•

• Industrial waste „cinder‟ is converted intoIndustrial waste „cinder‟ is converted into

light weight aggregate by secondary burning light weight aggregate by secondary burning and marketed in the name

and marketed in the name – – “AGLOPYRITE”.“AGLOPYRITE”.

•

• In India, Pune based company, In India, Pune based company, B.G.ShirkeB.G.Shirke Construction Company Ltd is manufacturing Construction Company Ltd is manufacturing steam cured, light weight, autoclaved and

steam cured, light weight, autoclaved and strong floor slabs, roof slabs, panels, lintels strong floor slabs, roof slabs, panels, lintels

etc. with the brand name “SIPOREX”.

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What is Light Weight

Concrete?

• •

“These

“These are the concretes which are much lighter than theare the concretes which are much lighter than the

conventional concrete, due to different constituents and

methods used in manufacturing

methods used in manufacturing process”process”..

Density of conventional concrete varies from 2400-2500

Kg/m3.But the density of light weight concrete is in between

300-1900 Kg/m3. How great difference !!!.

• •

“The

“The LWC is a concrete capable 0f LWC is a concrete capable 0f hardening, to a mass havinghardening, to a mass having

oven dry density not more than

oven dry density not more than 1800 Kg/m31800 Kg/m3 ””..

• •

“Concretes

“Concretes having a 28 days compressive strength in excess of having a 28 days compressive strength in excess of

175 Kg/m3 and 28 day air dried unit weight not exceeding 1850

Kg/m3

Kg/m3””..

Light weight concrete can be simply defined as follows, Light weight concrete can be simply defined as follows,

As per

As per RILEMRILEM, the light weight concrete committee, the light weight concrete committee

As per ACI, As per ACI,

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Advantages over Conventional concrete



 Reduction of Dead load due to less density.Reduction of Dead load due to less density.



 Increases progress of work due to less weight.Increases progress of work due to less weight.



 Lowers Haulage and Handling Lowers Haulage and Handling charges.charges.



 In extreme climatic conditions, use of In extreme climatic conditions, use of LWC is advisableLWC is advisable

because of high thermal insulation (due

because of high thermal insulation (due to porous ness).to porous ness).



 More sound and heat insulation.More sound and heat insulation.



 Its volume per unit weight is more than that of Its volume per unit weight is more than that of

conventional concrete, because of low density, results

conventional concrete, because of low density, results inin

economical

economical constructionconstruction..



 Due to low density, it reduces the size and the cost of Due to low density, it reduces the size and the cost of

structural members such as beams, columns,

foundations etc.



 This is advantageous in the case of tall structures whichThis is advantageous in the case of tall structures which

are to be constructed on soils

are to be constructed on soils of low bearing capacity.of low bearing capacity.



 It is eco-friendly because it gives an outlet for industrialIt is eco-friendly because it gives an outlet for industrial

waste such as clinker, fly ash, slag etc. which otherwise

create pollution.

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How to make concrete LIGHT ??

•

• Weight of concrete Wc is a function of weights of Weight of concrete Wc is a function of weights of aggregates, binder and volume of voids.

aggregates, binder and volume of voids.

Wc = f [ Wca, Wfa, Wb, Wv ]

Therefore, we can reduce the weight Wc by,

Therefore, we can reduce the weight Wc by, •

• Reducing the weight of coarse and fineReducing the weight of coarse and fine

aggregates, i.e. use of light weight aggregates

which are occurred either Naturally (Pumice) or

Artificially( Globulite, Terlite).

Artificially( Globulite, Terlite). •

• Increasing the volume of voids by one or Increasing the volume of voids by one or both of both of following,

following,

–

– Introducing air or gas into Introducing air or gas into the concretethe concrete –

– Remove certain fractions of fine aggregate in theRemove certain fractions of fine aggregate in the

concrete so that volume of void can be

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Classification

of

Light Weight Concrete

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Classification based on RILEM



Fully compacted concrete



Partially compacted concrete



No finer concrete



Aerated concrete produced by chemical

process (gas concrete)



Aerated concrete produced by physical process

(foam concrete)

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Classification based on density and

strength



L.W.C of Low strength and good thermal

insulation having density ranges from 250- 800

Kg/m3.



L.W.C. of medium strength and adequate

thermal insulation having density ranges from

800

800 _–

_–

1400 Kg/m3.



L.W.C. of structural strength and limited

thermal insulation having density ranges from

1400

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Methods of Production

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There are three methods to produce L.W.C.

They are,



Omitting

Omitting fine

fine sized

sized aggregates

aggregates while

while grading

grading

i.e.

No Fines Concrete.



Using

Using cellular

cellular porous

porous aggregates

aggregates

i.e.

i.e. Light

Light

Weight Aggregate Concrete.



Introducing air

or

or gas

gas in

in to concrete

to concrete

i.e. Aera

ted

Concrete.

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No Fines Concre

te



 fine aggregate fraction is omittedfine aggregate fraction is omitted



 Only cement and coarse aggregates are used (19mmOnly cement and coarse aggregates are used (19mm

_–

9mm). 9mm).



 It contains many uniformly distributed voids.It contains many uniformly distributed voids.



 Density varies from 2/3rd to3/4th of conventionalDensity varies from 2/3rd to3/4th of conventional

concrete concrete



 Strength mainly depends on W/C ratio and A/C ratio.Strength mainly depends on W/C ratio and A/C ratio.



 W/C W/C ratio ratio must must be be in in between between 0.38 0.38 to to 0.52 0.52 andand

A/C ratio must be in between 6:1 to 10:1. A/C ratio must be in between 6:1 to 10:1.

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

In case of No fines concrete, W/C ratio must

be selected very carefully



The density of No fines concrete varies from

1600-1900 kg/m3.



It can be reduced up to 360 kg/m3 by using

LWA

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Disadvantages



Possesses poor workability



Low compressive strength



Low flexural strength



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Light weight Aggregate

concrete



One of the oldest and

common method of

producing L.W.C



Light weight aggregates, either Natural or

Artificial,are used in concrete.

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Light Weight Aggregates

Natural Light weight aggregates:

These are naturally available aggregates, like These are naturally available aggregates, like

  PumicePumice   DolomiteDolomite   ScoriaScoria 

 Volcanic cinders Volcanic cinders



 Saw dustSaw dust



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

Expanded clay and shales

-

Produced by heating of Produced by heating of clay and shale

clay and shale heating up to point of incipient fusionheating up to point of incipient fusion Expanded slate

Expanded slate

-

Produced by heating rapidly to higherProduced by heating rapidly to higher temperature so as not allow gases to escape

temperature so as not allow gases to escape



Foamed blast furnace slag

Foamed blast furnace slag – – Cooling slag withCooling slag with

controlled amount of water, the steam is tapped inside the controlled amount of water, the steam is tapped inside the mass, results in L.W.A. known as foamed

mass, results in L.W.A. known as foamed slag or expandedslag or expanded slag.

slag.

Pulverized fuel ash

Pulverized fuel ash – – fly ash is mixed with limitedfly ash is mixed with limited

amount of water and made into pellets and then introduced amount of water and made into pellets and then introduced to a temperature of 1000-1200 degree c, from which it is to a temperature of 1000-1200 degree c, from which it is converted into aggregate. Most commonly used aggregate converted into aggregate. Most commonly used aggregate because of

because of it’sit’s _{high strength/ density ratio and less shrinkage}_{high strength/ density ratio and less shrinkage}

value. value.

Processed Natural L.W. Aggregates : Processed Natural L.W. Aggregates :

Processed Industrial byproduct L.W.A. : Processed Industrial byproduct L.W.A. :

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Aerated concrete

or

Cellular

concrete



General

composition

is

mortar,

suitably aerated

Called as foam concrete, cellular

concrete, gas cone etc.



In India, the factories manufacturing

aerated concrete are Siporex,

vayuthan, celcrete .

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

 Methods of aeration:Methods of aeration:

By the formation of gas by chemical By the formation of gas by chemical

reaction within the mass during liquid or reaction within the mass during liquid or plastic

plastic

state-Finely powdered Al or Zn is added to the slurry Finely powdered Al or Zn is added to the slurry

which in turn reacts with ca(OH)2 generated during which in turn reacts with ca(OH)2 generated during hydration of cement. H2 gas liberated by such

hydration of cement. H2 gas liberated by such reaction will lead to cellular concrete. It

reaction will lead to cellular concrete. It is usedis used normally in precast concrete factories

normally in precast concrete factories

By mixing preformed stable foam with By mixing preformed stable foam with

slurry-Stable foam is mixed with

Stable foam is mixed with slurry thus causingslurry thus causing cellular structure when the slurry sets

cellular structure when the slurry sets andand hardened. It is suitable for

hardened. It is suitable for small scale productionssmall scale productions and in situ works.

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Classification of Aerated

concrete :



 As per IS 6072As per IS 6072 _–_– 1971 and IS 60731971 and IS 6073 _–_– 1971, the aerated1971, the aerated

concretes are classified into five groups based on their concretes are classified into five groups based on their density, as follows

density, as follows GROUP

GROUP DRYDRY

DENSITY DENSITY Kg / m3 Kg / m3 Min. Min. Compressive Compressive Strength ( Strength ( Kg Kg // cm2) cm2) Class Class A A 851 851 to to 1000 1000 7070 Class Class B B 751 751 to to 850 850 6060 Class

Class C C 651 651 to750 to750 5050 Class

Class D D 551 551 to to 650 650 3535 Class

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Implementatio

n of

L.W.C

•

• Since the strength of L.W.C. is low, it is Since the strength of L.W.C. is low, it is used inused in the construction of roof slabs, small houses with

the construction of roof slabs, small houses with

load bearing walls etc.

load bearing walls etc. •

• It is also used in the It is also used in the construction of stairs,construction of stairs, windows, garden walls, etc.

windows, garden walls, etc. •

• In large buildings also, this is used in In large buildings also, this is used in thethe construction of partition walls.

construction of partition walls. •

• These are moulded in the form of slabs andThese are moulded in the form of slabs and used as thermal insulators inside the building.

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“

T

o r e a

l i s e

t h e lo w

c o

s t

c o

n s

t r u c t i o n ,

w

e

h a v e

t o im p

l e

m

e

n t L i g h

t w e i

g h

t

Concrete first”. Concrete first”.

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Conclusion :

•

• Since, the Light weight concrete is of lowSince, the Light weight concrete is of low compressive strength; this can not be used for

compressive strength; this can not be used for

the construction of structural members such as

beams, columns, etc. But this can be effectively

used in the construction of partition walls,

windows, floor slabs, etc. The implementation of

light weight concrete more in the structure leads

to more economy. Therefore we can conclude

that,

that, •

• ““To achieve the low cost construction, first weTo achieve the low cost construction, first we