flyash bricks.ppt

8/9/2019 FLYASH BRICKS.ppt

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CRACKS IN BUILDINGS

THE ROLE OF FLYASHBRICKS AND THEREMEDIES

PROF. (DR.) ANANTA KUMAR DASDEPARTMENT OF CHEMICAL ENGINEERING,

DURGAPUR INSTITUTE OF ADVANCEDTECHNOLOGY AND MANAGEMENT, DURGAPU


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INTRODUCTION


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Cracks in buildings are of common occurrence developed whenever stress in the component excstrength. This stress caused by external forces dead, live, wind, seismic loads and foundation setor induced internally due to thermal movements, changes, chemical actions, weathering actions resshrinkage or expansion of the bricks, mortar, con

due to corrosion of reinforcement etc. render the sunsafe. The other causes may be due to fault of sdesign. Fly ash brick, a building component haseect on these cracks that can be avoided manufactured and used properly.


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CLASSIFICATION OF CRACKS


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VERTICAL CRACKS

Develops due toshrinkae! e"pansion orther#al #ove#ent o$%ri&k! #ortar and&on&rete'

Do not endaner thesa$et( o$ the %uildin%ut unsihtl(

I#pression o$ $ault()ork#anship


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*ORI+ONTAL CRACKS

Develops #ainl( at the,un&tion o$ %ri&k#asonr( )ith RCC sla%

-eakens the&onstru&tion and

re.uires heav(repairin resultin hih&ost involve#ent


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STRUCTURAL

Fault( &onstru&tion

Overload

E"tensive &ra&kin o$ RCC%ea#

In&orre&t Desin

NON STRUCTURA

Internal indu&ed s%uildin #aterials

/enetration o$ #ois)eather a&tions thr#asonr( )orks

Resultin in shrin%ri&ks! #ortar! &on&r

Resultin &orrosirein$or&e#ent 0 in&rease in volu#e


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/ATTERN OF CRACKS


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CLASSIFICATIONS1

StraihtToothed

Stepped

Rando# Cra2in 3 O&&urren&e o$ &losel( spa&4ne &ra&ks at sur$a&e o$ a #aterial


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STRAI5*T

CRACKS


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TOOT*ED

CRACKS


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STE//ED

CRACKS


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RANDO6

CRACKS


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CRA+IN5


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CAUSES OF CRACKS


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A %uildin &o#ponent develops &)henever stress developed in the &o#poe"&eeds its strenth'

Exter!" !##"$e% &'re Due to dead! live! )ind or

seis#i& load

For#ation o$ settle#ent

Iter!" $%e% *t Due to ther#al #o

#oisture &hane and a&tions

In %uildin &o#ponent ledi#ensional &hanes

*ori2ontal #ove#ents' Due to volu#e &hane

&o#ponent resultin e"pansion or &ontra&tion

Co#pressive Tensile S7uildin &o#position


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SU78ECT TO CRACKIN5

6asonr(

Con&rete6ortar

-IDT* OF CRA

Thin 9 :;#

6ediu# 9;< ##

-ide 9=


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/RINCI/AL CAUSES OF CRACKS 7UILDIN5 >Non stru&tural?

Ther#al variation Che#i&al rea&tion

6oisture #ove#ent

Elasti& de$or#ation

Creep

Foundation #ove#ent 0 settle#ent o$ soil

Veetation

6anu$a&turin de$e&ts

Details in ne"t $e) slides


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T*ER6AL 6OVE6ENTS


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FACTORS AFFECTIN5

Te#perature variationDi#ensions

Coe@&ient o$ e"pansion

/h(si&al properties o$ the #ater


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COEFFICIENT OF T*ER6ALE/ANSION >;B3 C?

Cla( 7ri&k 0 7ri&k )ork 3GCe#ent #ortar 0 &on&rete ;B

Sand li#e %ri&ks ;;3;H

Fl( ash %ri&ks ;3;G


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SOME FACTORS INFLUENCING THERMAL CRACKING

a.Color & surface character!ato" reflect%t coeffce"t' re(uces heat loa

the roof

).Ther*al co"(uct%t

c.+ro%so" of a" "sulat"$ or ,rotect%e la

(.I"ter"all $e"erate( heat


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OTHER FACTORS INFLUENCING THERMAL CRACKING

Loss of heat ) ra(ato" "to the at*os,here (e,e"(s o" the ,ro,

e-,ose( surface to %olu*e of the co*,o"e"t. For "sta"ce f u"(e

co"(to"s " a /0 c* thc1 fl ash )rc1 2all 304 of heat s lost to the

hours u"(er s*lar crcu*sta"ces5 sa*e a*ou"t of heat 2ll )e lost " a

2ee1 2he" the 2all s /.0 * thc1 .

Ge"erall s,ea1"$ ther*al %arato"s " the "ter"al 2alls are "ot *uch

(oes "ot cause crac1"$. It s *a"l the e-ter"al 2alls es,ecall te-,ose( to (st"ct solar ra(ato" a"( the roof 2hch are su)6ect to su

ther*al %arato"s a"( are ths la)le to crac1"$.

Hor!o"tal crac1 at the su,,ort of a" RCC Roof sla) (ue to Ther*al *o%

sla)s.


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C*E6ICAL REACTIONS


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MO7EMENT 8UE TO CHEMICALREACTION

Solu)le sul,hates 2hch are so*et*es ,rese"t " $rou"( 2ater react 2th e-c)rc1s for* $,su* a"( calcu* alu*"ate sul,hate 2hch occu, *uch )$$er %

the or$"al co"sttue"ts. Ths e-,a"so" reacto" results " 2ea1e""$ of *aso

the" for*ato" of crac1s.

The se%ert of sul,hate attac1 (e,e"(s u,o" a*ou"t of solu)le sul,hate ,rese

fl ash )rc1s co"crete *ortar ,ro,orto" of C9A ,rese"t a"( (urato" for

co*,o"e"ts " :ua"tt re*a"s (a*,. If ,ure 2ater free of sul,hate s use( for *ash )rc1s the" sul,hate attac1 ca" )e a%o(e(. S*larl chlor(e co"te"t " 2

cell for*ato" " case of RCC a"( a$a" ,ro,a$ates the crac1s (ue to "crease "

The che*cal reacto" ,rocee(s %er slo2l a"( t *a ta1e a)out t2o to *ore

effect of ths reacto" )eco*es a,,are"t.


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SE7ERIT< OF SUL+HATE =CHLORATTACK

a.A*ou"t of solu)le sul,hate=Chlor(e ,re).+er*ea)lt of )rc1s co"crete *ortar

c.+ro,orto" of C9A ,rese"t

(.8urato" for 2hch the )ul("$ co*,o"

" :ua"tt re*a"s (a*,.


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6OISTURE 6OVE6ENT


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DRJ

S*RINKA5EVS FLJ AS* 9SAND3LI6ECO6/OSITIO

N


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FLJ AS*3SAND3LI6E 7RICKS VS C7RICKS


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ELASTIC DEFOR6ATION


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*(dration o$ li#e a$ter %ri&k $or#ation &aa redu&tion in the volu#e o$ the s(ste

sili&a 9 li#e 9 )ater to an e"tent o$ B'the volu#e o$ the dr( &o#pa&t' This isplasti& strain )hi&h aravates due to lo)ater %( evaporation that &auses su&ra&ks' I$ the proportions o$ ea&h &o#ponare properl( #i"ed this pro%le# )ill nelii%le $or #akin ( ash %ri&ks'


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CREE/


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The in&rease o$ strain o$ a &o#pa&t )ithunder sustained stress is ter#ed &reepshrinkae and &reep o&&urs si#ultaneous

The rate o$ &reep de&reases )ith ti#ethe $a&tors inuen&in &reep are si#il

shrinkae )hi&h are des&ri%ed later' In o$ ( ash %ri&ks Creep is nelii%le i$%ri&ks are #atured '


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FOUNDATION 6OVE6ENT 0SETTLE6ENT


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Fl( ash %ri&ks are not responsi%le $or thiso$ $ailure


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VE5ETATION3

The ro)th o$ un)anted plants in th

&onstru&tion #akes the &onstru&tion)eak' So an( ro)th o$ plant is to %estopped'Not related to ( ash %ri&ks


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S*RINKA5E

SHRINKAGE OF FL< ASH BRICK


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SHRINKAGE OF FL


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LIME= FL< ASH CONTENT

H$her the l*e $reater the (r"$ shr"1Co"%ersel lar$er the %olu*e of a$$relesser the shr"1a$e for )rc1s "creas"%olu*e of a$$re$ates ) /4 re(uctoshr"1a$e ) 04.So ,ro,er co*,osto)e *a"ta"e(.


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-ATER CONTENT

Greater the :ua"tt of 2ater use( " the$reater the shr"1a$e. Thus a 2et *-*ore shr"1a$e tha" a (r *- 2hcother2se s*lar. So )etter %)rato" = ,ressure $%es less shr"1a$e. O" the ha"( %arato" " the stre"$th 2ll occure.


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A55RE5ATES

B us"$ lar$est ,oss)le *a-*u* s!a$$re$ate " )rc1 a"( e"sur"$ $oo( $ra@ re:ure*e"t of 2ater s re(uce(. A$$re$that are ,orous a"( shr"1 o" (r"$ resh$her shr"1a$e


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ACCELERATORS

Accelerators l1e CaClE M$ClE s a((efaster reacto" to2ar(s slcate )o"("$use " h$h ,erce"ta$e o%er .0 tshr"1a$e coul( )e *ore. I" case of scur"$ the a((to" of accelerators ha"otcea)le *,act.


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CURIN5

+ro,er cur"$ shoul( )e (o"e starte( as so"tal set has ta1e" ,lace a"( t s to )e co"tfor at least for (as the" (r"$ shr"1a$e 2less )ecause 2he" har(e""$ ta1es ,lace *ost e"%ro"*e"ts the" there s "tall

e-,a"so" 2hch offsets a ,art of su)seshr"1a$e. Stea* cur"$ at the t*e*a"ufactur"$ re(uces the la)lt to shr"1ah$h l*e results " ,re?car)o"ato"

+RESENCE OF EDCESSI7E FOREI


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+RESENCE OF EDCESSI7E FOREIFINES

L1e Slt cla (ust shoul( "ot )e *ore th;4 " a$$re$ates )ecause t "crease suarea result"$ h$h 2ater re:ure*e"t ressta"t to )o"("$ " che*cal reacto".


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*U6IDITJ

Shr"1a$e s *uch less " coastal areas 2relat%e hu*(t re*a"s h$h. Lo2 rehu*(t causes ,lastc shr"1a$e.


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CE6ENT AS A CO6/ONENT

Ra,( har(e""$ ce*e"t to )e a%o(e( )ecause

$reater shr"1a$e tha" or("ar +ortla"( ce*

h$her ,ro,orto" of CaSO9 & lo2er ,ro,ort

al1als l1e so(u* o-(e a"( ,otassu* o-(e

use(. ++C ce*e"t s ,refera)le.

Other2se (ffere"ce " stre"$th (e%elo

)et2ee" fl ash )rc1s a"( ce*e"t *ortar 2ll

crac1s.


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TE6/ERATURE

If the te*,erature of the *- s lo2ere( 9C to /C t 2oul( results re(ucto" of re:ure*e"ts a"( he"ce lo2er shr"1a$e.thus follo2s that " a tro,cal cou"tres l1e )rc1 2or1 (o"e ) fl ash )rc1s " *l( 2

2oul( ha%e *uch less te"(e"c for cratha" that (o"e " hot su**er. So the a$$rea"( *-"$ 2ater shoul( )e sha(e( fro* su".

MEASURES FOR CONTROLLING


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MEASURES FOR CONTROLLINGCRACKS 8UE TO SHRINKAGE

O" accou"t of (r"$ out of *osture co"te"t " )ul("$ *

co*,o"e"ts.

Shr"1a$e " a *ateral "(uces te"sle stress 2he" there

restra"t to *o%e*e"t 2here the stress e-cee(s the s

crac1"$ occurs ths relat"$ the stress. Crac1s $et local!e(

secto"s such as (oor a"( 2"(o2 o,e""$ or starcase 2alls.

A%o("$ use of rch ce*e"t *ortar " *aso"r *a(e of

)rc1s. 8ela"$ ,laster 2or1 tll *aso"r has (re( after

cur"$. Shr"1a$e s *a(e to ta1e ,lace 2thout a" restra"t.

MEASURES FOR CONTROLLING


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MEASURES FOR CONTROLLINGCRACKS 8UE TO SHRINKAGE#Co

Coat of ,laster"$ o" *aso"r s restra"e( fro* shr"1a$e to so*

) ts a(hes%e )o"( to "o" shr"1"$ )ac1$rou"( the later ha%"$u"(er$o"e shr"1a$e.Shr"1a$e of a rch a"( stro"$ *ortar s 1"o2" to e-te"t suffce"ttear off the surface laer of 2ea1 )rc1s.I" su**er/ ce*e"t> sa"(I" 2"ter / ce*e"t> 0 sa"(

If a 2all e-cee(s 0?* le"$th ,ro%(e co"trol 6o"ts at 2ea1 secto"Cur"$ of *aso"r shoul( )e (o"e s,ar"$l to a%o( )o( of the$ett"$ 2et.

A%o( e-cess%e 2elt"$ of *aso"r at the t*e of ,laster"$ *osture (oes"t reach the )o( of the )loc1s.

DRJIN5 S*RININ5 OF FLJ AS*3


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DRJIN5 S*RININ5 OF FLJ AS*SAND3LI6E 7RICKS>Co#parison?

FRESH MI+TURE BRICK

STREN5T* G3M k< da(s

3;Bk

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