Prefabricated Concrete

8/9/2019 Prefabricated Concrete

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PREFABRICATED CONCRETE


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Prefabrication

It is a construction industry term used to describe assemblies that are manufactured

under factory conditions and then transported to construction sites for

incorporation into buildin and ci!il enineerin "or#s$

%enerally& there are t"o main types of pre cast concrete elements& mainly precast

reinforced concrete elements and precast prestressed concrete elements


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Normal castin process for precast reinforced or prestressed concrete elements '

Fabrication process Good practices

1. Assembly of mould Chec# the le!el and flatness of the

base mould before assemblin themould for panel castin$

Ensure that the dimensions of

mould are "ithin the specified

tolerances$

Chec# the s(uareness of the mould

form$

2. Mould cleaning and

preparation

The mould should be clean and

free from debris and old mortars

usin remo!er or scalin bars$

Form oil or mould release aent

should be applied e!enly o!er the

mould surface$


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Chec# that the )oints and edes of

the mould& bolts& stoppers& tie rods&

side props and rubber seal are

intact and properly secured$

3. Fixing of rebars/ cast in items/

prestressing strands

Chec# that the rebar si*e& spacin

and lap lenth are in accordance

"ith the dra"ins$


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Rebars& cast in items& corruated

slee!e pipes& recesses& liftin

hoo#s and inserts must be

correctly positioned and properly

secured$


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+se of fabrication ri can help to

ensure the accuracy of rebars

fi,in and spacin$

-ufficient number of spacers "ith

the correct si*es should beproperly placed and secured to

achie!e the re(uired concrete

co!er durin castin$

4. Final inspection before casting Chec# and !erify that all details

comply "ith dra"ins$


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Chec# the mould fittin conditions

includin bloc#out details$

5. oncreting Conduct slum test in compliance

"ith -- ./ to assess the

"or#ability of the concrete mi,

before placin the concrete to the

mould$


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The drop heiht of concrete mi,

should not e,ceed more than 0m$

Proper !ibration and compaction

should be carried out in particular&

in more conestion areas$

-preadin and le!elin of concrete

surface le!el after initial set$

+se of po"er tro"el1 float is

recommended for smooth surface

finishes$


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!. uring Obser!e ade(uate curin time and

desired en!ironment$

Concrete cubes should be

sub)ected to the same curin

conditions as the precast concrete

element$

". #emoulding Cube tests should be conducted to

!erify the concrete strenth of

elements before demouldin$

2oosen and remo!e all bolts and

pins and end and side mould forms

before liftin$

For prestressed elements& cut

strands before liftin$


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$. Final inspection / transfer to

storage yard

Finis%ing &or's before deli(ery to

site )

Chec# the condition of the

finished product


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Application of prefabricated concrete as foundation component in buildings-

Precast concrete systems can be used to rapidly construct foundations$ The

elements are usually to a bespo#e desin and cast in a factory en!ironment& i!inassured (uality for the finished product$ The foundations are often supported by

concrete piles and connected toether$

These systems impro!e producti!ity& especially in ad!erse "eather conditions& and

reduces the amount of e,ca!ation re(uired 3 particularly ad!antaeous "hen

dealin "ith contaminated round$

1. Precast Abutment

The precast concrete abutment is an 423shaped5 shallo" foundation component&

much li#e a con!entional bride beam seat$ -ections are produced in 67385sections and butt3)ointed toether to form loner abutments$ They are desined

for lateral earth pressure aainst one side and for the load transferred from the

beam and tread combination from the first span$This abutment component "ill

rest on a bed of compacted stone or an unreinforced cast in place pad 9a#a :mud

mat:; so that load can be transferred uniformly to the in situ soil$ These


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abutments contain a hori*ontal re!eal positioned to recei!e the first roo!e on

the ad)acent tread$ The beam seat of the abutment has a semi3circle shaped

!alley for proper seatin of the precast beams$

-hallo" foundation component

2. Precast concrete pier system

Precast piers are ad!antaeous to enineers and desiners for many reasons$

First& these relati!ely3liht components are easily handled in the field by

laborers or small liftin e(uipment$ Taller piers are achie!ed by addin risers to

the precast pier$ Typically > is a ma,imum total heiht for a precast pier$

-econd& precast piers allo" for fe"er disturbances to the sub rade and

surroundin areas than dri!in deep foundations$

-hallo" footin option

?ost cost3effecti!e

-tac#able components consistin of base& riser9s;& and cap

Can stac# additional risers up to 6$@> in heiht abo!e rade before additional

bracin is re(uired$


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3. Cast in-place Concrete Shallow ootings

Cast3in3place concrete shallo" footins are typically circular or s(uare& and

commonly formed "ith a -onotube form$ The -onotube 9or e(ual product; actsas a stay3in3place form$ The ad!antaes associated "ith concrete piles

9durability lone!ity; are reali*ed "ith this method$ Once constructed& the

precast caps are then attached to the top of the pier "ith a steel do"el and

epo,y connection& allo"in proper alinment of the beams !ia the pin

connectors$

-hallo" footin option

Typically more cost3effecti!e than a deep foundation option

Circular or s(uare


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Precast foundation "alls simplify basement construction& sa!e time and money&

and result in "armer& drier basements$ The "alls comprise hih3strenth concrete

panels manufactured off site$ Each panel contains solid concrete studs for load3

bearin support and a built3in concrete footin$ -ome panels include riid

insulation to #eep the basement "armer and rebar and polypropylene fibers forstrenth$ alls can be customi*ed by pro)ect to allo" for door and "indo"

openins& steel3beam poc#ets and bric# ledes$ ?anufacturers offer other

con!enience features such as built3in access for "irin and plumbin and "ood or

steel nailers for easy dry"all installation$ Panels rane in si*e from = to 0= feet

"ide by / to 0= feet hih to accommodate a !ariety of basement confiurations$

The cost of precast concrete systems is competiti!e "ith the cost of other

foundation "alls$ A precast concrete foundation is best3used to construct a full

basement "ith consistent sill heiht different "all heihts slo" the process&

minimi*in the cost benefit$ Installers "ho aren>t familiar "ith precast concretepanel assembly "ill need additional trainin$ -ome manufacturers allo" only

certified installers to deli!er and erect their systems$

Other features and benefits of precast foundation "alls include

*ime and labor sa(ings.A typical precast concrete foundation can be

erected in four to fi!e hours& about a si,th of the time needed for a formed3

concrete "all$ The panels can be erected in cold temperatures& "hich means

"eather delays aren>t an issue$ And there>s no on3site curin timethe "alls

can be bac#filled as soon as the slab and first3floor )oists are in place$

+tronger, lig%ter, safer &alls.Precast concrete panels are manufactured in

temperature3controlled en!ironments& "hich enables manufacturers to

produce concrete mi,es that harden to @& psi$ This is stroner than the

=&@3psi concrete in standard poured "alls and stroner than concrete

bloc#& yet the precast panels are thinner and of lihter "eiht$ Precast panel

systems also are more resistant to fire& termites& dry rot& and tornado and

hurricane damae than other foundation types$

-etter indoor comfort.Because many precast concrete panels are formed"ith interal riid insulation& little or no additional insulation is needed to

achie!e a "arm basement$ Precast panels also are lo"3maintenance and ha!e

better soundproofin characteristics than other foundation types$

aterresistant construction.The hih3strenth& lo"3"ater concrete mi,

used for precast panels is denser than typical concrete& ma#in it more


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"ater3resistant$ This helps #eep basements dry "ithout additional

"aterproofin$ In reions "ith hih rainfall& ho"e!er& local buildin codes

may re(uire additional "aterproofin$

Ten times stroner than bloc# foundation$

It pre!ents "ater infiltration and moisture built up$

They #eep houses "armer and drier than con!entional foundations "hile

addin !aluable li!in spaces and increasin resale !alue$

To enhance strenth and durability& they are manufactured "ith steel '

reinforced concrete studs& riid insulation& a reinforced top and bottom bond

beam "ith a = inch thic# concrete facin$ Foundations can often be installed in under fi!e hours usin a precast

concrete system$


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?anufacturin process


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Benefits of Precast Buildin Components

3 Consistency (uality throuh strinent (uality control in manufacturin process

3 Impro!e buildability

3 Impro!e construction speed shorter cycle time

3 -afer more orani*ed construction site en!ironment

3 Reduce "astae of materials

3 2ess labour intensi!e

Documents

Prefabricated Concrete