Development Of Light Weight Concrete.docx

8/17/2019 Development Of Light Weight Concrete.docx

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ABSTRACT

This paper deals with the development of two types of lightweight concrete the one using

lightweight aggregate (Pumice stone) and the other water floating type using Aluminium powder

as an air entraining agent. This also shows the importance of water/cement ratio as in first type of

concrete it relates to the smoothness of the surface and in second one it is a major factor which

controls the expansion of concrete.


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INTRODUCTION:

Lightweight concrete can e defined as a type of concrete which includes an expanding

agent in it that increases the volume of the mixture while reducing the dead weight. !t is lighter

than the conventional concrete with a dry density of "## $g/m" up to %&'# $g/m" . The main

specialties of lightweight concrete are its low density and low thermal conductivity.

There are many types of lightweight concrete which can e produced either y using lightweight

aggregate or y using an air entraining agent. !n this project ! have wor$ed on each of the aove

mentioned types. oth of them are nonstructural concrete.

1) By using Pumice stone as a lightweight aggegate:

Pumice stone is a lightweight aggregate of low specific gravity. !t is a highly porous

material with a high water asorption percentage. !n this we do not use the conventional

aggregate and replace it y the pumice stone.

!) By using Aluminium "ow#e as an ai entaining agent:

*ater floating aerated concrete is made y introducing air or gas into slurry composed of

Portland cement and sand+ so that when the mix sets and hardens+ uniform cellular structure is

formed. Thus it is a mixture of water+ cement and finely crushed sand. *e mix fine powder of

Aluminium to the slurry and it reacts with the calcium hydroxide present in it thus producing

hydrogen gas. This hydrogen gas when contained in the slurry mix gives the cellular structure

and thus ma$es the concrete lighter than the conventional concrete.

AD$ANTA%&:

Lightweight concrete is of utmost importance to the construction industry. The

advantages of lightweight concrete are its reduced mass and improved thermal and sound

insulation properties+ while maintaining ade,uate strength. The marginally higher cost of the

lightweight concrete is offset y si-e reduction of structural elements+ less reinforcing steel and

reduced volume of concrete+ resulting in overall cost reduction. The reduced weight has

numerous advantages one of them is reduced demand of energy during construction.

T'P&S O( I%*T+&I%*T CONCR&T&:

Using lightweight aggegates:

This type is produced using lightweight aggregate such as volcanic roc$ or expanded

clay. !t can e produced with the use of naturally mined lightweight aggregates (ul$ density in


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the range of & $g/m" ) or manmade lightweight aggregates li$e Aardelite0 or Lytag0 (ul$

density # $g/m" ).

Using ,oaming agents:

This one is produced through the addition of a foaming agent in cement mortar. This

creates a fine cement matrix which has air voids throughout its structure. Aerated cement mortar

is produced y the introduction of a gas into cementitious slurry so that after hardening a cellular

structure is formed.

T'P&S O( I%*T+&I%*T A%%R&%AT&:

Light weight aggregates used in structural lightweight concrete are typically expanded

shale+ clay or slate materials that have een fired in a rotary $iln to develop a porous structure.

1ther products such as air cooled last furnace slag are also used. Also there are some non

structural lightweight aggregates with lower density made with other aggregate materials and

higher air voids in the cement paste matrix. These are typically used for their insulation

properties.

Natual aggegates:

Inoganic Natual Aggegates: 2iatomite+ pumice+ scoria and volcanic cinders are natural+

porous volcanic roc$s with a ul$ density of 3## 4 # $g/m" which ma$e a good insulating

concrete

Oganic Natual Aggegates: *ood chips and straw can e mixed with a inder to provide a

lightweight natural aggregate. These are cellular materials which have air trapped within their

structures once they have low moisture content.

-anu,actue# aggegates:

%. loated clay+ sintered fly ash and foamed last furnace slag.

5. Lightweight expanded clay aggregate6 This is produced y heating clay to a temperature of

%### 4 %5## o 7+ which causes it to expand due to the internal generation of gases that are trapped

inside. The porous structure which forms is retained on cooling so that the specific gravity is

much lower than what was efore heating it.

(oaming agents:

There are some foaming agents which when added to the cement slurry forms air voids

throughout its structure. Also there are some agents who react with the chemicals present in the


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cement slurry and evolve gases which results in the expansion of the slurry and when it hardens+

leaves air voids in the concrete thus ma$ing it lighter than the normal concrete.

The ul$ density of fine lightweight aggregates is around %5## $g/m " .

The ul$ density of coarse lightweight aggregates is around 89# $g/m " .

%&N&RA PROP&RTI&S:

ight +eight:

2ensity range from 93# :g/m" to %&3# :g/m" as compared to %#:g/m" to 5'##

:g/m" for conventional ric$ and concrete respectively. 2espite millions of tiny air filled cells+ it

is strong and durale. There is Lightweight advantage for the structure design+ leading to savings

in supporting structures and foundation.

Com"essi.e Stength: 5.# to ;.# ince lighter than concrete ? ric$+ the lightness of the material increases resistance

against earth,ua$e.

Insulation:

>uperior thermal insulation properties compared to that of conventional ric$ and

concrete+ so reduces the heating and cooling expenses. !n uildings+ lightweight concrete will

produce a higher fire rated structure.

+oa2ility:

Products made from lightweight concrete are lightweight+ ma$ing them easy to place

using less s$illed laour. The ric$s can e sawed+ drilled and shaped li$e wood using standard

hand tools+ regular screws and nails. !t is simpler than ric$ or concrete.

i,es"an:

*eather proof+ termite resistant and fire proof.

Sa.ings in -ateial:

@educes dead weight of filler walls in framed structures y more than 3# as compared

to ric$wor$ resulting in sustantial savings. 2ue to the igger and uniform shape of loc$s+

there is a saving in ed mortar and plaster thic$ness. !n most cases the higher cost of the light


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weight concrete is offset y a reduction of structural elements+ less reinforcing steel and reduced

volume of concrete.

+ate A2so"tion:

7losed cellular structures and hence have lower water asorption.

Sim Coating:

2o not re,uire plaster and water repellent paint suffices. *allpapers and plasters can also

e applied directly to the surface.

-o#ulus o, &lasticity:

The modulus of elasticity of the concrete with lightweight aggregates is lower+ #.3 4 #.;3

to that of the normal concrete. Therefore more deflection is there in lightweight concrete.


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-ANU(ACTURIN%:

!t is produced y including large ,uantities of air in the aggregate+ matrix or in etween

the aggregate particles or y a comination of these processes. Lightweight aggregates re,uire

wetting prior to use to achieve a high degree of saturation. !f the aggregates arenBt fully saturated

they have a tendency to float towards the surface of the mix after it has een placed.

2ue to the higher moisture content of lightweight concrete+ drying times are typically longer

than regular concrete. Typically+ a #.3 water to cement ratio slurry is used as a ase mixture for

lightweight concrete. The water cement ratio varies according to specific project re,uirements.


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not prevent the need for external curing.>tructural lightweight concrete has een used for ridge

dec$s+ piers and eams+ slas and wall elements in concrete and steel uildings+ par$ing

structures+ tiltup walls+ topping slas and composite slas on metal dec$ing.


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AUTOCA$&D A&RAT&D CONCR&T& USIN% AU-INIU- PO+D&R 3AAC)

Autoclaved Aerated 7oncrete (AA7) or Autoclaved Lightweight 7oncrete (AL7) is a precast

construction material that is made from a variety of aggregate parts no larger than sand. At

roughly onefifth of the weight of normal concrete+ it is an incredily lightweight uilding

material. !t provides excellent thermal and acoustic resistance and also protects against

household ha-ards as termites and fire. AA7 is commonly referred to as autoclaved cellular

concrete ecause hydrogen ules form during the production process+ resulting in small

poc$ets of air within the concrete that sustantially increase the volume of the final concrete

product. Though the precise composition of autoclaved aerated concrete may vary+ it is generally

made up of ,uart- sand or some other fine aggregate+ cement and water or some other inding

component and aluminium powder. The aluminium powder reacts with the cement and forms

hydrogen ules to form within the mix+ therey increasing the volumetoweight ratio of the

concrete mix. After the mix is cast into the desired form and the volumeincreasing chemical

reactions occur+ the concrete mix+ which is still soft+ is autoclaved.

-ANU(ACTURIN% PROC&SS:

The raw materials are atched y weight and delivered to the mixer. Eeasured amounts

of water and expansive agent are added to the mixer and the cementitious slurry is mixed.

>teel moulds are prepared to receive the fresh AA7. !f reinforced AA7 panels are to e

produced+ steel reinforcing cages are secured within the moulds. After mixing+ the slurry is

poured into the moulds. The expansive agent creates small+ finely dispersed voids in the fresh

mixture+ which increases the volume y aout 3# percent in the moulds within three

hours.*ithin a few hours after casting+ the initial hydration of cementitious compounds in the

AA7 gives it sufficient strength to hold its shape and support its own weight. After cutting+ the

aerated concrete product is transported to a large autoclave+ where the curing process is

completed. Autoclaving is re,uired to achieve the desired structural properties and dimensional

staility. The process ta$es aout eight to %5 hours under a pressure of aout %;' psi (%5 ars)

and a temperature of aout %o 7.


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T&C*NICA SP&CI(ICATIONS:

2ensity6 "## to %9## $g per cum F this is light enough to float in water

7ompressive strength6 "## to 8## psi

Allowale shear stress6 & to 55 psi

Thermal resistance6 #.& to %.53 per in. of thic$ness

>ound Transmission 7lass (>T7)6 '# for ' in. thic$ness '3 for & in. thic$ness

T&C*NICA P&R(OR-ANC&:

(ie Resistance:

Autoclaved aerated concrete provides the highest security against fire and meets the most

stringent fire safety re,uirements. 2ue to its purely mineral composition+ AA7 is classified as a

noncomustile uilding material. !t is oth resistant to fire up to %5##o 7 and heat resistant.

Stuctual Pe,omance:

Autoclaved aerated concrete is strong and durale despite its lightweight. AA7Bs solidity

comes from the calcium silicate that encloses its millions of air pores and from the process of

curing in a pressuri-ed steam chamer+ an autoclave. !ts excellent mechanical properties ma$e it

the construction material of choice for earth,ua$e -ones.

Soun# Insulation:

AA7 has excellent sound insulation properties compared to other uilding materials with

the same weight.

Dua2ility:

!t retains its properties for the entire life of a uilding and can resist wind+ earth,ua$e+

rain (also acid rain)+ storm and a wide range of external temperatures.

AD$ANTA%&S:

!t has een refined into a highly thermally insulating concreteased material used for oth

internal and external construction. esides AA7Bs insulating capaility+ one of its advantages in

construction is its ,uic$ and easy installation+ for the material can e routed+ sanded and cut to

si-e on site using standard caron steel and saws+ hand saws and drills.

Sustaina2le Constuction

The choice of the right uilding material is one of the $ey factors for sustainale

uildings. AA7 is a uilding material which offers considerale advantages over other


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construction materials. !ts high resource efficiency gives low environmental impact in all phases

of its life cycle+ from the processing of raw materials to the disposal of AA7 waste.

&n.ionmental Pe,omance:

Resouces:

AA7 is made from naturally occurring materials that are found in aundance 4 lime+ fine

sand+ other siliceous materials+ water and a small amount of aluminium powder (manufactured

from a yproduct of aluminium). Curthermore the production of AA7 demands relatively small

amounts of raw materials per m" of product+ and up to a fifth as much as other construction

products.

&n.ionmental im"act #uing "o#uction:


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light weight+ autoclaved aerated concrete is not widely produced+ so it may e difficult for many

to otain it locally. !t must also e coated with some form of protective material+ as it tends to

degrade over time ecause of its porous nature.

US&S:

!t is a lightweight+ precast uilding material that simultaneously provides structure+ insulation+

and fire and mould resistance. AA7 products include loc$s+ wall panels+ floor and roof panels

and lintels.

US& O( AU-INIU- PO+D&R:

The reactants in aerated concrete are lime (which is present in cement) and aluminium

powder. *hen the aluminium powder is added to slurry of lime+ hydrogen is produced in the

form of ules. Thic$ slurry is made with lime/cement along with aggregates. Aluminium

powder is added in the final stage of mixing. The mix is poured into moulds. The moulds are

autoclaved which imparts strength. AA7 is produced using no aggregate larger than sand.

Guart- sand+ lime and/or cement and water are used as a inding agent. Aluminium powder is

used at a rate of #.#3 4 #.#& y volume of cement.

The hydrogen gas foams and doules the volume of the raw mix (creating gas ules up to %/&

inch in diameter). At the end of the foaming process+ the hydrogen escapes into the atmosphere

and is replaced y air. 2epending on its density+ up to of the volume of an AA7 loc$ is air.

AA7Bs low density also accounts for its low structural compression strength. !t can carry loads

up to %+5## Psi+ approximately only aout %# of the compressive strength of regular concrete.

AA7 material can e coated with a stucco compound or plaster against the elements. >iding

materials such as ric$ or vinyl siding can also e used to cover the outside of AA7 materials.

&5P&RI-&NTS O( AAC:

>ince the autoclave0 facility was unavailale at the place where ! was wor$ing+ ! did not

autoclave my samples and thus was unale to find its actual strength.


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The mix design for the first sample was decided ased on studies. Then further samples were

made y changing some proportions in the previous ones.


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Sample no. 1: !n this the cement/sand ratio ta$en is %6%. Also the w/cm ratio ta$en is #.'.

Aluminium powder is #.' 4 #.3 y weight of cement.

7ement (1P7)6 %.#& $g

>and6 %.#& $g

*ater6 ''# gm

Aluminium powder6 ' 4 3 gm

The mixture was hot just after mixing which confirmed the chemical reaction in that. Also

hissing sound was coming which confirmed the evolution of gas. >ince this is aerated concrete+ it

should expand. ut it did not. The reason was less amount of water since it did not form slurry

and there were gaps etween the particles through which all the evolved gases escaped out from

the concrete. These gases should remain there only so that the concrete expands ut it did not

happen.

>o for the next sample+ ! increased the w/cm ratio to ma$e the slurry.

Sample no. 2: *ith w/cm ratio H #.'3

7ement (1P7)6 3'# gm

>and6 3'# gm

*ater6 5'" gm

Aluminium powder6 " gm

This mixture made slurry which was easily flowing. !n this just after filling the cue the initial

depth of the top surface of the slurry was %%.3 cm. After just 3 minutes+ the depth was %# cm

which showed that it expanded as we predicted.

*eight of the sample6 %.%' $g

Iolume6 %3 x %3 x 3 cm"

2ensity6 %#%"."" $g/m"

Sample no. 36 To reduce density further+ ! decreased the ,uantity of sand.

7ement (PP7)6 %# gm

>and6 8'# gm

*ater6 '8# gm

Aluminium powder6 9 gm


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!n this sample the initial depth of the top surface of the slurry was 9.& cm and just after 3 minutes

the depth was " cm.

*eight of the sample6 5.#5 $g

Iolume6 %3 x %3 x %5 cm"

2ensity6 ;'&.%3 $g/m"

This was floating in water.

Sample no. 4: !n this new sample ! tried to use Pumice >tone powder and reduced the ,uantity of

sand in the mixture. !n this sample ! had to use more ,uantity of water since pumice stone

asors water.

7ement (PP7)6 %# gm

>and6 &'# gm

Pumice >tone Powder6 %5# gm

*ater6 99# gm

Aluminium powder6 9 gm

!n this sample the initial depth of the top surface of the slurry was &.9 cm and the final depth was

'.3 cm.

*eight of the sample6 5.#' $g

Iolume of the sample6 %3 x %3 x %#.3 cm"

2ensity6 &9".'8 $g/m"

Sample no. 5: >ample of 5 cues.

7ement6 %95#J5 H "5'# gm

>and6 %59#J5 H 535# gm

Pumice stone powder6 %J5 H "9# gm

*ater6 853J5 H %&3# gm

Aluminium powder6 8J5 H %& gm


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Sample no. 6: >ample of 5 cues

7ement6 %589J5 H 5385 gm>and6 %##&J5 H 5#%9 gm

Pumice stone powder6 %''J5 H 5&& gm

*ater6 ;'#J5 H %' gm

Aluminium powder6 ;J5 H %' gm

=ere the initial depth of top surface of oth the cues was 9 cm and the final depth was # cm.

*eight of each cue6 5.'3 $g

Iolume of each cue6 %3 x %3 x %3 cm"

2ensity6 ;53.85 $g/m"


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>o in all+ sample numers "+ '+ 3 and 9 were the successful ones. They all were floating in water.


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I%*T+&I%*T CONCR&T& USIN% PU-IC& STON&:

The word KPumiceB is a general term used for a range of porous materials produced

during volcanic eruptions. Pumice stone can e wea$ and porous or strong and less porous. !ts

water asorption is as high as 33 since it is a highly porous material. The major reason ehind

using pumice as an aggregate is its much light weight and comparatively high strength.

Pumice stone6 light+ spongy+ highly porous $ind of lava with a vitreous texture. Pumice has high

silica ? al$ali and low calcium ? magnesia content. !ts spongy cellular texture is a result of the

gases escaping from hot lava. !t is having low strength and it is a good thermal insulator+ sound

insulator and fire insulator.

T&STS ON I%*T+&I%*T CONCR&T& USIN% PU-IC& STON& AS A

I%*T+&I%*T A%%R&%AT&:

Cor this project+ we got pumice stone as ig as 3# mm si-e. >o we crushed it to the si-e

less than 5# mm.

The mix design for the first sample was decided ased on studies. Then further samples

were made y changing some proportions in the previous ones.

Sample no. 1: % cue

7ement6 %.%& $g

>and6 5.9" $g

Pumice6

( %# mm)6 38# gm

('.;3 4 %# mm)6 8%# gm

(M '.;3 mm)6 %33 gm

*ater6 %5"# gm


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" days cue testing6

>.no+ *eight of cue(:g)+ Load ($trength (EPa).

%+ ".8'+ 5".%+ %.#".

Cor calculating water asorption y pumice stone6

Ta$e a sample of pumice stone in a uc$et and note down its dry weight. Then fill the uc$et

with enough water and let it remain as it is for 39 hours. Then remove the excess water and note

down the wet weight of the stones. The two weights will give us the water asorption y the

pumice stone.

2ry weight6 "&& gm

*et weight6 9#' gm

water asorption6 (wet weight 4 dry weight) N %## / (dry weight) H 33.9;

Sample no. 2: % cue considering water asorption and using admixture. !n this ! reduced the

,uantity of sand to further reduce the density of the concrete and to compensate the effect of

reduced fines+ used more amount of pumice less than '.;3 mm.

7ement6 % $g

>and6 9## gm


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Pumice6

( %# mm)6 9## gm

('.;3 4 %# mm)6 '"# gm

(M '.;3 mm)6 "## gm

*ater6 %"## gm

Admixture6 9 gm

The admixture used was K>i$a Iiscocrete 3##%B. This made water release from cement

particles.After opening it we found that its finish was not good. >ome areas were smooth and

some were not. !ts reason came out to e the larger particles of pumice stone. >o next time ! did

not use particles igger than %# mm.

Sample no. 3: for " cues using aggregates less than %# mm.

7ement6 "3'# gm

>and6 %# gm

Pumice (smaller than %# mm)6 '%## gm

*ater6 "'## gm

Admixture6 5% gm

These cues had low density and also smooth surface.


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; days cue testing6

>.no+ *eight of cue(:g)+ 2ensity(:g/m" )+ Load ($trength (EPa)

%+ '.5+ %5''.''+ %9".#+ ;.5'

5+ '.'+ %"#".;#+ %'&.'+ 9.9#

Sample no. 46 >ample for 5 cues.

7ement6 "3'# gm

>and6 5%## gmPumice6

('.;3 4 %# mm)6 5% gm

(M '.;3 mm)6 %8"# gm

*ater6 "'## gm

Admixture6 %' gm


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*eight of each cue6 '&&5 gm

Iolume of each cue6 %3 x %3 x %3 cm"

2ensity6 %''9.3% $g/m"

>o in all+ sample numers " and ' were the successful ones. Their finish was good and they were

light also.


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CONCUSION

ased on the aove experiments and samples made+ following has een concluded6

%) The Aerated concrete is a much lighter concrete and can float on water. !t does not contain

coarse aggregates. !t is composed of cement+ sand+ high watercement ratio and aluminium

powder. Oust as we mix the aluminium powder in the cementsand slurry+ the expansion in the

volume can e oserved. *ithin 3 minutes it expands y "#. !t consists of many pores and thus

is not structurally strong. !t is a good insulator of heat and sound and thus can e used in place of

conventional ric$s or at the places which does not ear any load.

5) The lightweight concrete manufactured using Pumice stone as a lightweight aggregate is half

the denser than the normal concrete. !n this the normal coarse aggregates are replaced y pumice

stone aggregate having si-e less than %# mm. !ts surface is flat and smooth and showing a good

finish. Although it cannot e used as a structural concrete ut its cue test results show

considerale strength and can e used as an architectural concrete. !t is a good insulator of heat

and sound and thus has the same uses as of the aove aerated concrete.


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R&(&R&NC&S

%) Amuja :nowledge 7entre Lirary. Amuja 7ements Ltd.

5) >amuel reen+ aveney. Pumice aggregate for structural

lightweight and internally cured concretes

") :eertana. + >ini >ara Eani and E. Thenmo-hi. Dtili-ation of ecosand and fly ash in aerated

concrete for a richest mix design

') =jh :amsiah Eohd.!smail+ Eohamad >ha-li Cathi and tudy of

lightweight concrete ehavior

3) =andoo$ on aerated concrete products y PTQ Ltd

9) iuseppe 7ampione and Lidia La Eendola. ehavior in compression of lightweight fire

reinforced concrete confined with transverse steel reinforcement (5##5)

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Development Of Light Weight Concrete.docx