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FORTA® ECONO-NET® is used to reduce *$astic and "ardened concrete s"rinkage# i)*ro(e

i)*act strengt"# increase !atigue resistance and concrete toug"ness/ T"is )ediu)-dut !i+er

o!!ers good-+onding *oer# $ong-ter) dura+i$it# and true secondar0te)*erature contro$ +

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FORTA® ECONO-NET® is )ain$ used in concrete a**$ications suc" as s$a+-on-grade#

o(er$as0to**ings# cur+s# s$o*e *a(ing# dri(eas# sidea$ks# +ase)ent !$oors# garage !$oors#

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contro$ te)*erature0s"rinkage cracking "i$e i)*ro(ing +asic dura+i$it *ro*erties/ Re4uires No

Mi5 6esign or P$ace)ent C"anges1

!NSTAAT!ON

Reco))ended dosage rate o! FORTA® ECONO-NET® is %/7 $+s/ *er cu+ic ard ,&/8 kg/ *ercu+ic )eter. o! concrete added direct$ to t"e concrete )i5ing sste) during# or a!ter# t"e

+atc"ing o! t"e ot"er ingredients and )i5ed at t"e ti)e and s*eed reco))ended + t"e )i5er

)anu!acturer ,usua$$ !our to !i(e )inutes./

P"#S!CA P$OPE$T!ESMaterials% 9irgin :o)o*o$)er Po$*ro*$ene

For&% Co$$ated Fi+ri$$ated Fi+er

Secific (ravit)% &/8%

Te*sile Stre*+t,% ;


3/19


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contri+ution $e(e$ t"at cou$d +e considered as signi!icant to t"is

$ong-ter) dura+i$it goa$/

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6/19

Polypropylene Fiber Reinforced Concrete : An Overview

The capailit# of ,urale structure to resist .eathering action/ che0ical attac*/

arasion an, other ,egra,ation processes ,uring its service life .ith the 0ini0al

0aintenance is e1uall# i0portant as the capacit# of a structure to resist the loa,s

applie, on it2 Although concrete offers 0an# a,vantages regar,ing 0echanical

characteristics an, econo0ic aspects of the construction/ the rittle ehavior of the

0aterial re0ains a larger han,icap for the seis0ic an, other applications .here

fle3ile ehaviour is essentiall# re1uire,2 Recentl#/ ho.ever the ,evelop0ent of

pol#prop#lene fier-reinforce, concrete 4PFR%5 has provi,e, a technical asis for

i0proving these ,eficiencies2 This paper presents an overvie. of the effect of

pol#prop#lene 4PP5 fiers on various properties of concrete in fresh an, har,ene,

state such as co0pressive strength/ tensile strength/ fle3ural strength/ .or*ailit#/

on, strength/ fracture properties/ creep strain/ i0pact an, chlori,e penetration2

The role of fiers in crac* prevention has also een ,iscusse,2

* , *in&/ Scientist/ Structural Engineering ivision/ %entral &uil,ing Research

(nstitute/ Roor*ee 6 7onorar# Secretar# (nstitute of Engineers/ Roor*ee

.ntroduction

%era0ics .ere the first engineering 0aterials *no.n to 0an*in, an, the# still

constitute the 0ost use, 0aterials in ter0s of .eight 89/ ):2 7#,raulic ce0ents an,

ce0ent-ase, co0posites inclu,ing concretes are the 0ain cera0ic-ase,

0aterials2 %oncrete offers 0an# a,vantages in the application ,ue to its i0prove,

0echanical characteristics/ lo. per0eailit# an, higher resistance against che0ical

an, 0echanical attac*s2 Although concrete ehavior is governe, significantl# # its

co0pressive strength/ the tensile strength is i0portant .ith respect to the

appearance an, ,urailit# of concrete2 The tensile strength of concrete is relativel#


7/19

0uch lo.er2 Therefore/ fiers are generall# intro,uce, to enhance its fle3ural tensile

strength/ crac* arresting s#ste0 an, post crac*ing ,uctile ehaviour of asic

0atri32

%oncrete 0o,ification # using pol#0eric 0aterials has een stu,ie, for the pastfour ,eca,es 8;:2 (n general/ the reinforce0ent of rittle uil,ing 0aterials .ith

fiers has een *no.n fro0 ancient perio, such as putting stra. into the 0u, for

housing .alls or reinforcing 0ortar using ani0al hair etc2 !an# 0aterials li*e jute/

a0oo/ coconut/ rice hus*/ cane agasse/ an, sa.,ust as .ell as s#nthetic

0aterials such as pol#vin#l alcohol/ pol#prop#lene 4PP5/ pol#eth#lene/ pol#a0i,es

etc2 have also een use, for reinforcing the concrete 8/?/@:2 Research an,

,evelop0ent into ne. fier reinforce, concrete is going on to,a# as .ell2

Pol#prop#lene fiers .ere first suggeste, as an a,0i3ture to concrete in 9>= for

the construction of last resistant uil,ings for the $S %orps of Engineers2 The fier

has suse1uentl# een i0prove, further an, at present it is use, either as short

,iscontinuous firillate, 0aterial for pro,uction of fier reinforce, concrete or a

continuous 0at for pro,uction of thin sheet co0ponents2 Since then the use of

these fiers has increase, tre0en,ousl# in construction of structures ecause

a,,ition of fiers in concrete i0proves the toughness/ fle3ural strength/ tensile

strength an, i0pact strength as .ell as failure 0o,e of concrete2 Pol#prop#lene

t.ine is cheap/ aun,antl# availale/ an, li*e all 0an0a,e fiers of a consistent

1ualit#2

Properties of Pol/prop/lene Fibers

The ra. 0aterial of pol#prop#lene is ,erive, fro0 0ono0eric %;7> .hich is purel#

h#,rocaron2 (ts 0o,e of pol#0eriBation/ its high 0olecular .eight an, the .a# it

is processe, into fiers co0ine to give pol#prop#lene fiers ver# useful properties

as e3plaine, elo. 8:C

• There is a stericall# regular ato0ic arrange0ent in the pol#0er 0olecule an,

high cr#stallinit#2 ue to regular structure/ it is *no.n as isotactic

pol#prop#lene2

• %he0ical inertness 0a*es the fiers resistant to 0ost che0icals2 An#

che0ical that .ill not attac* the concrete constituents .ill have no effect on the

fier either2 On contact .ith 0ore aggressive che0icals/ the concrete .ill

al.a#s ,eteriorate first2


8/19

• The h#,rophoic surface not eing .et # ce0ent paste helps to prevent

choppe, fiers fro0 alling effect ,uring 0i3ing li*e other fiers2

• The .ater ,e0an, is nil for pol#prop#lene fiers2

• The orientation leaves the fil0 .ea* in the lateral ,irection .hich facilitates

firillations2 The ce0ent 0atri3 can therefore penetrate in the 0esh structure

et.een the in,ivi,ual firils an, create a 0echanical on, et.een 0atri3 an,

fier2

Figure 9C 0onofila0ent

fier

Figure )C Firillate,

fier

The fiers are 0anufacture, either # the pulling .ire proce,ure .ith circular cross

section or # e3tru,ing the plastic fil0 .ith rectangular cross-section2 The# appear

either as firillate, un,les/ 0ono fila0ent or 0icrofila0ents as sho.n in Fig2 9 6

)2 The properties of these three t#pes of PP fiers are given in Tale 9 89D:2 The

firillate, pol#prop#lene fiers are for0e, # e3pansion of a plastic fil0/ .hich is

separate, into strips an, then slit2 The fier un,les are cut into specifie, lengths

an, firillate,2 (n 0onofila0ent fiers/ the a,,ition of uttons at the en,s of thefier increases the pull out loa,2 Further/ the 0a3i0u0 loa, an, stress transfer

coul, also e achieve, # t.isting fiers 899:2

Role of Fibers

%rac*s pla# an i0portant role as the# change concrete structures into per0eale

ele0ents an, conse1uentl# .ith a high ris* of corrosion2 %rac*s not onl# re,uce the

1ualit# of concrete an, 0a*e it aestheticall# unacceptale ut also 0a*e structures

out of service2 (f these crac*s ,o not e3cee, a certain .i,th/ the# are neither

har0ful to a structure nor to its serviceailit#2 Therefore/ it is i0portant to re,uce

the crac* .i,th an, this can e achieve, # a,,ing pol#prop#lene fiers to concrete

89;:2 The ri,ging of crac*s # the a,,ition of PP fiers has een sho.n in Fig ;2

Thus a,,ition of fiers in ce0ent concrete 0atri3 ri,ges these crac*s an, restrains

the0 fro0 further opening2 (n or,er to achieve 0ore ,eflection in the ea0/

a,,itional forces an, energies are re1uire, to pull out or fracture the fires2 This


9/19

process/ apart fro0 preserving the integrit# of concrete/ i0proves the loa,-carr#ing

capacit# of structural 0e0er e#on, crac*ing2 This i0prove0ent creates a long

post-pea* ,escen,ing portion in the loa, ,eflection curve as sho.n in Fig < 89):2

Reinforcing steel ars in concrete have the sa0e eneficial effect ecause the# act

as long continuous fires2 Short ,iscontinuous fires have the a,vantage/ ho.ever/of eing unifor0l# 0i3e, an, ,isperse, throughout the concrete2

The 0ajor reasons for crac* for0ation are Plastic shrin*age/ Plastic settle0ent/

FreeBe tha. ,a0age/ Fire ,a0age etc2

Plstic s&rin0e1 (t occurs .hen surface .ater evaporates efore the lee,

.ater reaches the surface2 Pol#prop#lene fiers re,uce the plastic shrin*age crac*

area ,ue to their fle3iilit# an, ailit# to confor0 to for02 The a,,ition of D29 #

volu0e of fiers is foun, effective in re,ucing the e3tent of crac*ing # a factor of

=-9D2 The e3tent of crac* re,uction is proportional to the fier content in the

concrete2

Tble 21 Properties of vrious t/pes of pol/prop/lene fibers

Fiber t/pe #ent&

3445

6i4eter

3445

Tensile

strent&

3MP5

Modulus of

elsticit/

37P5

*pecific

surfce

348905

6ensit/

309c4:5

0onofila0en

t

;D-=D D2;D-D2;= =


10/19

Figure ;C &ri,ging of crac* using Pol#prop#lene fiers Figure Do% creating voi,s in the concrete2 The vapor pressure is release,

in ne.l# for0e, voi,s an, e3plosive spalling is significantl# re,uce, as sho.n in fig

=89


11/19

&efore 0i3ing the concrete/ the fier length/ a0ount an, ,esign 0i3 variales are

a,juste, to prevent the fiers fro0 alling2 Goo, FR% 0i3es usuall# contain a high

0ortar volu0e as co0pare, to conventional concrete 0i3es2 The aspect ratio for

the fiers are usuall# restricte, et.een 9DD an, )DD since fiers .hich are too

long ten, to "all" in the 0i3 an, create .or*ailit# prole0s2 As a rule/ fiers aregenerall# ran,o0l# ,istriute, in the concrete ho.ever/ placing of concrete shoul,

e in such a 0anner that the fiers eco0e aligne, in the ,irection of applie,

stress .hich .ill result in even greater tensile an, fle3ural strengths2 There shoul,

e sufficient co0paction so that the fresh concrete flo.s satisfactoril# an, the PP

fiers are unifor0l# ,isperse, in the 0i3ture2 The fiers shoul, not float to the

surface nor sin* to the otto0 in the fresh concrete2 %he0ical a,0i3tures are

a,,e, to fier-reinforce, concrete 0i3es pri0aril# to increase the .or*ailit# of the

0i32 Air-entraining agents an, .ater-re,ucing a,0i3tu- res are usuall# a,,e, to

0i3es .ith a fine aggregate content of =D or 0ore2 SuperplasticiBers/ .hen a,,e,

to fier-reinforce, concrete/ can lo.er .aterC ce0ent ratios/ an, i0prove the

strength/ volu0etric stailit# an, han,ling characteristics of the .et 0i32 The

properties of PFR% .ith various fier volu0e are sho.n in Tale )2

Tble 8 Mec&nicl Properties of Pol/prop/lene Fiber Reinforced Concrete

'

o

Concrete 4i


12/19

)@

;2D2<

=

;>D

4OP%5

99DD

4)D00

5

>


13/19

==2;

;

=?29

9

>2@<

2D2;

D

=>?

4OP%5>;D 9D=D

Superplastic

iBer

4Paric

FP;DD$5

%#lin,er

Firillate,

4> 00 long

6 D2D> 00

,ia5

9D

D

D

D2)

=

D2=

D

@92>

D

>D2@

D

>D2D

D

D

;?2)

D

-

-

-


14/19

Effects on Fres& Concrete

The 0ain para0eter/ .hich is often use, to ,eter0ine the .or*ailit# of fresh

concrete/ is the slu0p test2 The slu0p value ,epen,s 0ainl# on the .ater

asorption an, porosit# of the aggregates/ .ater content in the 0i3ture/ a0ount of

the aggregate an, fine 0aterial in the 0i3ture/ shape of the aggregates an,surface characteristics of the constituents in the 0i3ture2 The slu0p values

,ecrease significantl# .ith the a,,ition of pol#prop#lene fiers as sho.n in Tale ;2

The concrete 0i3ture eco0es rather cling# resulting in increasing of the a,hesion

an, cohesiveness of fresh concrete2 uring 0i3ing the 0ove0ent of aggregates

shears the firillate, fiers apart/ so that the# open into a net.or* of lin*e, fier

fila0ents an, in,ivi,ual fiers2 These fiers anchor 0echanicall# to the ce0ent

paste ecause of their large specific surface area2 The concrete 0i3ture .ith

pol#prop#lene fiers results in the fe.er rate of lee,ing an, segregation as

co0pare, to plain concrete2 This is ecause the fiers hol, the concrete together

an, thus slo. ,o.n the settle0ent of aggregates2 ue to its high tensile an, pull-

out strength/ the PP fiers even re,uce the earl# plastic shrin*age crac*ing #

enhancing the tensile capacit# of fresh concrete to resist the tensile stresses cause,

# the t#pical volu0e changes2 The fiers also ,istriute these tensile stresses

0ore evenl# throughout the concrete2 As the plastic shrin*age crac*ing ,ecreases/

the nu0er of crac*s in the concrete un,er loa,ing is re,uce,/ ,ue to ,ecrease in

crac*s fro0 the e3isting shrin*age crac*s2 (f shrin*age crac*s are still for0e,/ the

fiers ri,ge these crac*s/ re,ucing at the sa0e ti0e their length an, .i,th2

!oreover/ as the rate of lee,ing ,ecreases/ the use of pol#prop#lene fiers 0a#

accelerate the ti0e to initial an, final set of the concrete as this le, to a slo.er rate

of ,r#ing in the concrete 892?@

3445

.nitil slu4p

3445

Finl slu4p

3445

Fiber lent&

3445

D

9;D

9?D

9)?

9)

?D

9)D

<

=9

=9

;D

=9

=9

9

Effects on rdened Concrete


15/19

The a,,ition of pol#prop#lene fires in the concrete ,i, not significantl# affect the

co0pressive strength an, the 0o,ulus of elasticit# ut the# ,o increase the tensile

strength2 Splitting tensile strength of PFR% appro3 ranges fro0 to 9; of its

co0pressive strength2 A,,ition of PP fiers in concrete increases the splitting

tensile strength # appro3 )D to =D 89>:2

Co4pressive strent&1 The co0pression strength of concrete is a vital para0eter

as it ,eci,es the other para0eters li*e tension/ fle3ure etc2 The effect of

pol#prop#lene fier on the co0pressive strength of concrete has een ,iscusse, in

0an# literatures an, oserve, that pol#prop#lene fier either ,ecreases or

increases the co0pressive strength of concrete/ ut overall effect is negligile in

0an# cases2 (n fact/ the effect of a lo. volu0e of pol#prop#lene fier on the

co0pressive strength of concrete 0a# e conceale, # the e3peri0ental error2

FleC Fracture shape

of plain concrete

Figure ?C Fracture shape

of PFR concrete

Bond strent&1 (t is necessar# that there shoul, e a goo, on, et.een the fier

an, the 0atri32 (f the critical fier volu0e for strengthening has een reache, then

it is possile to achieve 0ultiple crac*ing2 This is a ,esirale situation ecause it

changes a asicall# rittle 0aterial .ith a single fracture surface to fracture into a

pseu,o ,uctile 0aterial .hich can asor transient 0inor overloa, an, shoc*s .ith


16/19

little visile ,a0age2 So the ai0 is to pro,uce large nu0er of 0ultiple crac*s at as

close spacing as possile so that the crac* .i,ths are ver# s0all/ al0ost invisile to

na*e, e#e so that the rate at .hich aggressive 0aterials can penetrate the 0atri3

is re,uce,2 7igh on, strength helps to give close crac* spacing ut it is also

essential that the fiers shoul, give sufficient ,uctilit# to asor i0pacts2 &ut inter0s of ph#sioche0ical a,hesion there is no on, et.een the fier an, the

ce0ent gel2 The use of choppe, an, t.iste, firillate, pol#prop#lene fiers .ith

their open structure has partiall# re0e,ie, the lac* of interfacial a,hesion #

0a*ing use of .e,ge action at the slightl# open fier en,s an, also # 0echanical

on,ing through firillation2 The general pull out loa,s of t.iste, firillate, fiers

8)D/ )9: 0a# range fro0 ;DD-=DDN for co00onl# use, staples ut the accurate

calculation of on, strength is co0plicate, # a lac* of *no.le,ge of the surface

area of fier in contact .ith the paste2 (t is oserve, that in ,a0age, pro,ucts an,

in ro*en speci0ens/ usuall# fier rea*s instea, of fier pull out 8:2

Frcture Properties1 The failure ehaviour of high-strength concretes is

effectivel# i0prove, # the use of fiers2 The t#pical shear on, rupture ,ue to

strain localiBation coul, e avoi,e, 4fig2 >52 (nstea, of this/ a large nu0er of the

longitu,inal crac*ing/ .hich .as pre,o0inantl# oriente, in the ,irection parallel or

su-parallel to the e3ternal co0pressive stresses/ .as for0e, at the entire concrete

speci0ens as sho.n in fig?2

%reep an, shrin*age properties of concreteC Fiers re,uce creep strain/ .hich is

,efine, as the ti0e-,epen,ent ,efor0ation of concrete un,er a constant stress2

%o0pressive creep values/ ho.ever/ 0a# e onl# 9D to )D of those for nor0al

concrete2 Shrin*age of concrete/ .hich is cause, # the .ith,ra.al of .ater fro0

concrete ,uring ,r#ing/ is also re,uce, # fiers2 The shrin*age/ creep an, total

ti0e ,epen,ent ,efor0ation of various PFR% 0i3es along .ith non firous concrete

0i3 are presente, in fig @89=:2 The re,uction in shrin*age ,ue to the presence of

fiers is e3pecte, fro0 nu0er of vie.points2 First/ the fiers ,o not e3hiit an#

shrin*age/ thus re,ucing overall shrin*age of the 0i32 (n a,,ition the fiers have a

role in retaining the .ater in the concrete 0i3 upto a certain li0it .hich helps to

,ela# the shrin*age2 Therefore a,,ition of fiers to the concrete 0i3es is al.a#s

a,vantageous in re,ucing shrin*age ,efor0ation2


17/19

Figure @C Ti0e ,epen,ent ,efor0ation of

pol#prop#lene fiers

Figure9DC Effect of pol#prop#lene fiers on i0pact resistance

of concrete

Fle # researcher89D:2 The i0pact resistance for

concretes .ith various volu0e fractions of firillate, pol#prop#lene fiers has een

sho.n in figure 9D2 The results in,icate that significant i0prove0ent in i0pact

resistance of concrete can e achieve, .ith relativel# lo. volu0e fraction of

pol#prop#lene fiers2

Tble 1 .4pct properties of fiber reinforced concrete

T/pe of 4i< Vf = Avere .4pct nu4ber

Avere filure

.4pct nu4ber .4pct ductilit/ inde<

%ontrol D )=2@ )>2@ 92D<

!icrofila0ent

D2D=

D2D

=

D29<

;

;@29

2=

;D2<

92D=


18/19

!onofila0ent

9

92)

92<

>@2

?D2?

>)2@

))

9D2D@

9;2);

C&loride penetrtion1 &esi,es i0prove, 0echanical properties ,ue to inclusion of

fier/ chlori,e penetration is also re,uce, sustantiall# # the presence of fiers

,epen,ing upon its orientation2 Antoni 89?: stu,ie, the effect of chlori,e

penetration an, foun, that the effect is insignificant for shorter fier ,ue to the

ran,o0 orientation of short fiers as co0pare to long fiers2 Further/ the chlori,e

0ove0ent into concrete is re,uce, significantl# # the presence of fier as the

interfacial transition Bone in the ,irection perpen,icular to the chlori,e penetration

.hereas fier provi,es easier path for the chlori,e to 0igrate in ,irection along the

fier2

Obstcles in Use of PFRC

Although PP fiers are gaining .i,e applications in 0an# fiel,s/ there is still nee,

for i0prove0ent in so0e properties2 A 0ajor fire .ill leave the concrete .ith

a,,itional porosit# e1ual to the volu0e of fiers incorporate, in the concrete

usuall# in the or,er of D2; to 92= # volu0etric fraction2 (n respect of

0onofila0ent fiers/ the poor on, et.een fier an, 0atri3 results in a lo. pull

out strength2 The PP fiers are also attac*e, # sunlight an, o3#gen/ ho.ever

surroun,ing concrete in PFR% protects the fiers so .ell that this shortco0ing is not

significant2 Further/ so0eti0es the fiers function as initiator of the 0icro crac*ing

ecause of their lo. 0o,ulus of elasticit# as co0pare, to the ce0ent 0atri32 Thus

0echanical on, .ith the ce0ent 0atri3 is also lo.2 The fiers cause the

enhance0ent of the pores volu0e of concrete # creating 0ore 0icro-,efects in

the ce0ent 0atri32

Conclusion

(nnovations in engineering ,esign an, construction/ .hich often call for ne.

uil,ing 0aterials/ have 0a,e pol#prop#lene fier-reinforce, concrete applications2

(n the past several #ears/ an increasing nu0er of constructions have een ta*en

place .ith concrete containing pol#prop#lene fires such as foun,ation piles/prestresse, piles/ piers/ high.a#s/ in,ustrial floors/ ri,ge ,ec*s/ facing panels/

flotation units for .al*.a#s/ heav#.eight coatings for un,er.ater pipe etc2 This has

also een use, for controlling shrin*age 6 te0perature crac*ing2

ue to enhance perfor0ances an, effective cost-enefit ratio/ the use of

pol#prop#lene fiers is often reco00en,e, for concrete structures recentl#2 PFR% is


19/19

eas# to place/ co0pact/ finish/ pu0p an, it re,uces the reoun, effect in spra#e,

concrete applications # increasing cohesiveness of .et concrete2 &eing .holl#

s#nthetic there is no corrosion ris*2 PFR% sho.s i0prove, i0pact resistance as

co0pare, to conventionall# reinforce, rittle concrete2 The use of PFR% provi,es a

safer .or*ing environ0ent an, i0proves arasion resistance in concrete floors #controlling the lee,ing .hile the concrete is in plastic stage2 The possiilit# of

increase, tensile strength an, i0pact resistance offers potential re,uctions in the

.eight an, thic*ness of structural co0ponents an, shoul, also re,uce the ,a0age

resulting fro0 shipping an, han,ling2

Ac0no(led4ent

The author .ishes to e3press his sincere than*s to !s Sonal hanvija# 6 !s

+e,anti Gan.ir of +isvesvara#a National (nstitute of Technolog#/ Nagpur for their

valuale help in preparing this paper2

fibrillated microfibers

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