Cement & concrete.ppt

7/25/2019 Cement & concrete.ppt

1/26

Cement & concreteCement & concrete


2/26

ConstituentConstituent SymbolSymbol %%

TricalciumTricalcium

SilicateSilicate

CC33SS 4545

DicalciumDicalcium

SilicateSilicate

CC22SS 3030

TricalciumTricalcium

AluminateAluminate

CC33AA 1010

TetracalciumTetracalcium

aluminofeerialuminofeeritete

CC44AFAF 88

t!erst!ers ""


3/26

Cement contd.Cement contd.

Portland cement consists of a number ofPortland cement consists of a number ofsilicate mineralssilicate minerals

Cement mixed with water sets as a functionCement mixed with water sets as a function

of time due to several hydration reactionsof time due to several hydration reactions Water binds the sheet like silicateWater binds the sheet like silicate

molecules together, thereby hardening themolecules together, thereby hardening thecementcement

Concrete sized aggregate of rocksConcrete sized aggregate of rocksembedded in a cement matrix, which bindsembedded in a cement matrix, which bindsthe rock pieces togetherthe rock pieces together


4/26

PolymersPolymers

Many simple molecules (monomer) unite toMany simple molecules (monomer) unite togive a big molecule, called polymergive a big molecule, called polymer

Organic polymers thousands of monomersOrganic polymers thousands of monomersare united by covalent bonds formed by carbonare united by covalent bonds formed by carbon

Because electrons are strongly bonded, theyBecause electrons are strongly bonded, theyare localized and polymers are thermal andare localized and polymers are thermal and

electrical insulatorselectrical insulators Relatively inert do not corrode due toRelatively inert do not corrode due to

covalent bondingcovalent bonding


5/26

PolymersPolymers

ClassificationClassification (i) thermoplasts (ii) thermosets(i) thermoplasts (ii) thermosets !hermoplasts!hermoplasts

"ong chain polymerization, proceeds linearly"ong chain polymerization, proceeds linearly have increasing plasticity, i#e#, increasing ability tohave increasing plasticity, i#e#, increasing ability to

deform plastically $ith increasing temperaturedeform plastically $ith increasing temperature

"ong chain molecules are held together by secondary"ong chain molecules are held together by secondarybondsbonds %econdary bonds bet$een the chains are bro&en more%econdary bonds bet$een the chains are bro&en more

readily therefore easily mouldable and finally meltsreadily therefore easily mouldable and finally melts


6/26

Polymers contd.Polymers contd.

Thermosets:Thermosets:

Three dimensional net work of primary bondsThree dimensional net work of primary bondsbecause polymerization proceeds in all directionsbecause polymerization proceeds in all directions

Relatively hard at room temperature and do notRelatively hard at room temperature and do notsoften on heatingsoften on heating

Become harder due to completion of any let-overBecome harder due to completion of any let-overpolymerization reactionpolymerization reaction

ecompose before melting due to their reactionecompose before melting due to their reactionwith atmospheric o!ygenwith atmospheric o!ygen

"!: Bakelite used for electrical insulation"!: Bakelite used for electrical insulation


7/26

#ong chain polymers#ong chain polymers

$lassification$lassification

%i& Plastics %ii& fibers %iii& elastomers%i& Plastics %ii& fibers %iii& elastomers

Plastics:Plastics:

'o directional property ( long chain molecules are'o directional property ( long chain molecules are

randomly orientedrandomly oriented

)ibers:)ibers:

*ll chains are more or less aligned in the long*ll chains are more or less aligned in the long

direction of the fiber -direction of the fiber - uni+ue directional propertyuni+ue directional property


8/26

$ontd.$ontd.

"lastomers:"lastomers:

#ong chain molecules e!hibiting the#ong chain molecules e!hibiting the

uni+ue rubbery behaviouruni+ue rubbery behaviour,tructure of long chain polymers:,tructure of long chain polymers:

-$$- -$-$--$$- -$-$-

# #

# #

# #

# #


9/26

Contd#

sp. hybridization ( tetrahedrally bonded

$1

$2

$3

$4 monomer


10/26

Contd#

egree of polymerization

This is the 'o. of repeating monomers in a

chain

/.wt of polymer degree of polymerization !

m.w of

monomer /.w in the range 01 111 to 0 111 111


11/26

'ame /onomer unit

R0 R2 R R3

4ses

Polyethylene

%polythene&

5 5 5 5 ,heets6tubes6

$ontainers

Polyvinyl chloride

%P7$&

5 5 5 $l "lectricalinsulation6gramaphonerecords

Polypropylene 5 5 5 $5 Ropes6filaments6vacuumflasks6flashlight

casings

Polymethylmethacrylate%Ple!iglass&

5 5 $5$88$5

Transparentwindows 9fi!tures

Polystyrene 5 5 5 $5; ,tyrofoam6 sound


12/26

Polytetrafluoroethylene%PT)"&

%Teflon&

) ) ) ) $oating for fryingpans6 razors andbearings6

chemicalware6humanbody implants

Poyacrylonitrile

%8rlon&

5 5 5 $' *crylic fiber usedas woolsubstitute inclothings


13/26

Polyamide fibersPolyamide fibers

-$ ( ' - linkage--$ ( ' - linkage-

"!: nylon %6& ('5%$5"!: nylon %6& ('5%$522&&::'5$8%$5'5$8%$522&&33$8-$8-

5ydrogen bonding between ad


14/26

C#2 C#2 C#2 C#2 C

C#2 C C#2 C#2 C#2

#

C#2 C#2 C#2 C#2 C

C#2 C#2 C#2 C#2 C#2

#


15/26

Polyester fibersPolyester fibers

' C ' lin(a)e ' terylene or *acron ' C ' lin(a)e ' terylene or *acron

++, is -resent in t!e bac(bone c!ain, is -resent in t!e bac(bone c!aininstea* of +C, ' -ro.i*es /eibility 'instea* of +C, ' -ro.i*es /eibility '

-olyester softens easily it!-olyester softens easily it!

increasin) tem-erature in s-ite ofincreasin) tem-erature in s-ite of

t!e !y*ro)en bon*in) beteent!e !y*ro)en bon*in) beteen

c!ainsc!ains


16/26

cellulosecellulose

Main constituent of wood is theMain constituent of wood is the

cellulose chain the monomercellulose chain the monomer

formula is:formula is:

CHCH22OHOH

CH OCH O

- O CH CH - O CH CH CH CHCH CH

HO OHHO OH


17/26

$ontd.$ontd.

> *lignment of long chains gives wood its highlydirectional properties

> Tensile strength more in the longitudinal

direction compared to transverse direction> Rayon-i.e.6 regenerated cellulose is natural

cellulose rendered highly crystalline

> $otton is related to natural plant fiber

> ?f the wrinkles in the long chain molecules ofcotton are removed permanently6 shrink (resistant6 sanforized cotton is obtained


18/26

'atural rubber'atural rubber

> ?soprene is the monomer unit

> ,ide groups in the monomer are both on

the same side of the molecule ( this is the

reason for the natural tendency for the

molecule to bend and promote rubbery

behavior

#

C C ' C C C ' C C ' C #

# # #

# C#3 # # # C#3#

#


19/26

$ontd.$ontd.

> 'atural rubber tapped from tree is a viscousli+uid ( long isoprene molecules are able to flowpast one another at room temperatures

> Raw rubber heated with @,A gives elastomer (cross linking takes place ( the process is calledvulcanization6 remaining double bond also getssaturated

> egree of vulcanization determines the stiffness

of rubber> $ross links increased ( rubber becomes more

rigid


20/26

$ontd.$ontd.

> "!: cycle tube is less vulcanized than a

rubber tyre

> =hen all the double bonds are used up by

sulfur bridges6 a three dimensional

network of primary bonds results

> "!: ebonite ( hard and brittle


21/26

$rystallinity of long chain polymers$rystallinity of long chain polymers

Long chain polymers usually non-Long chain polymers usually non-

crystalline or in the semicrystallinecrystalline or in the semicrystalline

formform

Non-crystalline form long chainsNon-crystalline form long chains

are randomly twisted with oneare randomly twisted with one

anotheranother


22/26

$rystallinity of long chain polymers$rystallinity of long chain polymers

Semicrystalline parts of the polymerSemicrystalline parts of the polymerolume hae the parallel chainolume hae the parallel chainarrangement! while other parts arearrangement! while other parts arerandomly orientedrandomly oriented

Sometimes single crystals of polymers canSometimes single crystals of polymers can"e grown crystals hae a folded chain"e grown crystals hae a folded chainstructure! where the same chain folds "ac#structure! where the same chain folds "ac#and forth many times into a paralleland forth many times into a parallelarrangementarrangement

Single crystal of polythene has anSingle crystal of polythene has anorthorhom"ic unit cellorthorhom"ic unit cell


23/26

/aking a crystal of polymer/aking a crystal of polymer

$n all polymers! long chains can "e aligned$n all polymers! long chains can "e alignedto some e%tent "y mechanical wor#ing to some e%tent "y mechanical wor#ing such an alignment promotes crystallinitysuch an alignment promotes crystallinity

High density polyethylene&sp'gr' (')*+High density polyethylene&sp'gr' (')*+ $n crystalline form! chains are more$n crystalline form! chains are more

closely pac#ed density increases withclosely pac#ed density increases withincreasing alignment of the chains! ,(increasing alignment of the chains! ,(crystalline+crystalline+

Low density polyethylene &sp'gr' (')2+Low density polyethylene &sp'gr' (')2+ Less than .( crystalline compared toLess than .( crystalline compared to

high density polyethylenehigh density polyethylene


24/26

$ryatallinity %contd.&$ryatallinity %contd.&

Crystallinity is also promoted "y theCrystallinity is also promoted "y the

formation of a hydrogen "ondformation of a hydrogen "ond

"etween chains instead of wea#er"etween chains instead of wea#er

an der /aals "ond'an der /aals "ond' 0%: nylon and cellulose crystalli1e0%: nylon and cellulose crystalli1e

due to the hydrogen "ond'due to the hydrogen "ond'


25/26

'actors promoting noncrystallinity

7ery long chains get tangled %coiled& easily (more difficult to crystallize

Branching impedes crystallization ( prevents

the parallel arrangement of chains necessaryfor crystallization

?rradiation of polymers can knock off a smallside group such as hydrogen6 where the end

of another molecule can be bonded6producing a branched structure ( branchingmakes the polymer stiffer


26/26

Dierent arran)ements ofDierent arran)ements of

-olymers-olymers Atactic lar)e si*e )rou-s are ran*omlyAtactic lar)e si*e )rou-s are ran*omly

arran)e* on eit!er si*e of t!e c!ain 'arran)e* on eit!er si*e of t!e c!ain 'crystalliation is *i6cult because t!ecrystalliation is *i6cult because t!earran)ement *oes not allo nei)!borin) c!ainsarran)ement *oes not allo nei)!borin) c!ains

to come closer all alon) t!e len)t! of t!e c!ainto come closer all alon) t!e len)t! of t!e c!ain 7sotactic all t!e bul(y )rou-s are arran)e* on7sotactic all t!e bul(y )rou-s are arran)e* ont!e same si*et!e same si*e

Syn*iotactic bul(y si*e )rou-s alternate onSyn*iotactic bul(y si*e )rou-s alternate oneit!er si*e of t!e c!ain in a re)ular fas!ioneit!er si*e of t!e c!ain in a re)ular fas!ion

7sotactic an* syn*iotactic -romote crystallinity7sotactic an* syn*iotactic -romote crystallinityCo-olymer to or more monomers areCo-olymer to or more monomers are

-olymerie* to)et!er-romote noncrystallinity-olymerie* to)et!er-romote noncrystallinity

Documents

Cement & concrete.ppt