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De La Salle University – Manila

Civil Engineering Department

Construction Materials and Testing

CIVMATL - EH

Reaction Paper 

Submitted byMae!ann E" Cuartero

##$$$%&'

Submitted to

Sir Ric(ard )e *esus

T(e +orldbe, is one o t(e e.ents (eld in t(e P(ilippines /(ic( e,(ibits constructione0uipment1 building materials1 interior design and ot(er products or business .enture" 2ound in

+orldbe, /ere some o t(e ne/ inno.ations /(ic( may (elp sol.e or lessen engineering

 problems" 3ne item /(ic( can be ound on t(e e,(ibit is a micro-rebar" T(is ne/ inno.ation can

(elp impro.e concrete strengt( and can possibly lessen large crac4s in concrete1 /(ic(

e.entually yields to ailure"

 

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T(e booming industry in construction1 /it( an #5"$67 increase in $%#8 according to

P(ilippine Statistics Aut(ority1 (as led to t(e dierent inno.ations in impro.ing concrete" T(ere

are se.eral actors to be considered in producing concrete" Ho/e.er1 t(e t(ree main component

considered includes strengt(1 cost and ser.iceability" In t(e strengt( category1 concrete can be

designed to attain a (ig( compressi.e strengt( but lo/ on tensile strengt(" In order to

compromise a lo/ tensile strengt(1 concrete is reinorced /it( steel bars1 or also 4no/n as

rebars" Reinorcing concrete /it( continuous steel bars aims to 4eep t(e concrete longer in its

elastic un-crac4ed p(ase" Ho/e.er1 /(en corrosion and temperature increase occurs on t(e

reinorcements1 t(e bond bet/een t(e concrete and rebar is lessened resulting to t(e ormation o 

crac4s" +(en it comes to cost and ser.iceability1 a reinorced concrete 9RC: can be designed to

 be durable by increasing its resistance to delection and controlling t(e occurrence o crac4s

9;ilbert1 $%%#:" Along /it( an increase in ser.iceability is t(e increase in cost o t(e resulting

structure"

)espite t(e ad.antageous uses o reinorcement bars1 e,periments s(o/ t(at suc( rebars

do not entirely pre.ent t(e crac4ing o concrete nor is capable o (olding crac4 /idt(s <to

acceptable design limits at economically lo/ reinorcement ratios= 9Heli,:" Aiming to disco.er 

somet(ing t(at /ill increase a concrete>s strengt(1 impro.e its perormance under stress /(ile

reduce its cost (as been t(e topic o researc( no/adays" T(roug( ad.ance tec(nology and

engineers1 Heli, /as able to disco.er a micro rebar /(ic( increases durability and crac4 

resistance o concrete"

Heli, micro rebar (as been irstly used in t(e ?nited States and (as been recently

introduced in t(e P(ilippines" T(e (eli, micro bar (as a lengt( o $@ mm /it( an e0ui.alent

diameter o %"@ mm" It is rectangular in cross-section and it (as a minimum o one '% degree

t/ist per (eli, micro rebar as s(o/n in 2igure #" T(e (eli, micro rebar comes by /eig(t" T(ereare about $@1 '%6 o ibers per 4ilogram o t(ese micro rebars" It is added to t(e concrete mi, by

gradually mi,ing it /it( t(e mi," Heli, pro.ided a mi,ing instruction in t(eir /ebsite"

According to (eli,1 t(e (eli, micro rebars s(ould be added at a rate o 8@-% seconds per 8@ lbs

9$% 4gs:" It s(ould also enter t(e mi,er /it(out any clump" Clumps larger t(an $ inc(es s(ould

 be a.oided" 2or a site batc(ing1 (eli, is t(e inal component to be added in t(e mi, /it( a mi,ing

speed o % re.olutions in @ minutes" Ho/e.er1 or a pan mi,er or a drum mi,er1 t(e ollo/ing

steps are ollo/ed or mi,ing in o (eli, micro rebar B# t(e mi,er is set to its proper speed" B$

t(e (eli, is added per dosing" B' it is added along /it( t(e aggregates B8 ater (eli, is added1

t(e ma, speed in mi,ing is maintained or @ minutes"

Ater mi,ing1 t(e concrete mi, is ready or placing" According to (eli,1 t(ere are no

special re0uirements in terms o placing t(e Heli, reinorced concrete" Placement can be directly

rom a mi, truc41 t(roug( a pump truc4 or e.en as a s(otcrete" Moreo.er1 clumps s(ould be

monitored during pouring to a.oid inconsistencies and to maintain uniormity"

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It is said t(at (eli, micro rebar can be a substitute or t(e traditional reinorcement bars"

E,periments perormed by Heli, s(o/ed t(at certain impro.ements (a.e de.eloped in concrete

/(en (eli, micro rebar is used rat(er t(an t(e traditional rebars" An e,ample /ould be t(e eect

o t(e (eli, micro rebar on t(e mec(anical properties o reinorced concrete" It (as been obser.ed

t(at t(e splitting tensile strengt( increases /(en concrete is incorporated /it( (eli, micro rebar"

Moreo.er1 /(en t(e (eli, reinorced concrete undergoes bending stress1 it e,(ibits a ductile

response but possess e0ual bending strengt( /it( t(at o t(e traditional RC" It also (as an elastic

design /(ic( results to a (ig(er allo/able stress" Suc( impro.ements occur because o t(e

 proacti.e resistance o t(e (eli, micro rebar" It acts li4e a scre/ /(ic( needs to be t/isted beore

it can be pulled out" Ater being in t(e proacti.e p(ase1 it /ill be in a reacti.e p(ase as s(o/n in

2igure $" )uring t(e reacti.e p(ase1 it e,(ibits a stable post pea4 tensile resistance" T(is means

t(at t(e micro rebars react in t(e ormation o crac4s" It /ill /or4 on a crac4 e.en beore it can

 be .isually seen"

Comparing t(e traditional RC /it( t(e (eli, RC1 t(e ormer tends to crac4 at %7 o 

load" A crac4 /ill e,pose t(e concrete to possible concrete attac4s li4e corrosion" Corrosion /ill

e.entually lead to t(e reduction o bond bet/een t(e concrete and t(e reinorcement itsel /(ic(

can lead into ailure as time progress" 3n t(e ot(er (and1 in using synt(etic ibers1 t(e small

impro.ements /(en it comes to strengt( /ere obser.ed" It may e,(ibit a good be(a.ior during

 plastic s(rin4age /(ic( occurs $8 (ours rom curing (o/e.er1 it acts as .oids until stretc(ed" 2or 

steel and iber reinorced concretes1 t(ere is at least a # to $ mm crac4s produced beore t(e

de.elopment o ull tensile strengt(1 according to Heli, 9reer to 2igure ':" Apparently1 or a

(eli, RC1 it already de.elops ull tensile strengt( at a crac4 e0ual to %"%%%@ mm" It (as a steel

/ire tensile strengt( o $6% 4si or #6%% MPa" Moreo.er1 it appro,imately (as ' gDm '  o 

electroplated inc coating /(ic( ma4es it resistant to rust"

3.erall1 t(e (eli, micro rebar resulted into a $@%7 increase in s(ear strengt(1 #%7

increase in irst crac4 strengt(1 @%7 or durability and $%7 cost sa.ings according to +es

At4inson o Century concrete" Aside rom t(e increase in perormance1 it (as decreased t(e

install time" It (as been applied to piers and arc(es in ot(er countries" Ho/e.er1 it s(ould be 4ept

in mind t(at t(e (eli, micro rebar does not replace cold !oints or isolation !oint /(ic( yield

concentrated stresses" +it( t(is ne/ inno.ation1 traditonal reinorcing o concrete can possibly

 be substituted /it( (eli, micro rebar since it (as e,empliied an increase in perormance1 a

decrease in installation time and a decrease in cost"

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2igure #" Heli, Micro Rebar 2igure $" Trend o Proacti.e and Reacti.e P(ase o 

Heli,

 

2igure '" Crac4 /idt( or ull tensile 2igure 8" Sample concrete /it( (eli, micro

strengt( de.elopment rebar  

Reerences

FGote Some numerical data come rom a C) gi.en by Heli,

;ilbert1 I" 9$%%#:" Shrinkage, Cracking and Deflection-the

Serviceability of Concrete Structures" Retrie.ed Marc( #@1 $%#@

rom

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Heli, 9$%#@:" Helix Micro Rebar  on C) R3M" 2is(er Martin

Tec(nologies1 Inc"

(ttpDD/eb%"psa"go."p(DcontentDconstruction-statistics-appro.ed-

 building-permits-ourt(-0uarter-$%#8-preliminary-results

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