Non-Destructive Evaluation of the Concrete Prefabricated ...
Prefabricated Concrete
Transcript of Prefabricated Concrete
-
8/9/2019 Prefabricated Concrete
1/17
PREFABRICATED CONCRETE
-
8/9/2019 Prefabricated Concrete
2/17
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
-
8/9/2019 Prefabricated Concrete
3/17
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$
-
8/9/2019 Prefabricated Concrete
4/17
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$
-
8/9/2019 Prefabricated Concrete
5/17
Rebars& cast in items& corruated
slee!e pipes& recesses& liftin
hoo#s and inserts must be
correctly positioned and properly
secured$
-
8/9/2019 Prefabricated Concrete
6/17
+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$
-
8/9/2019 Prefabricated Concrete
7/17
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$
-
8/9/2019 Prefabricated Concrete
8/17
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$
-
8/9/2019 Prefabricated Concrete
9/17
!. 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$
-
8/9/2019 Prefabricated Concrete
10/17
$. Final inspection / transfer to
storage yard
Finis%ing &or's before deli(ery to
site )
Chec# the condition of the
finished product
-
8/9/2019 Prefabricated Concrete
11/17
Application of prefabricated concrete as foundation component in buildings-
Precast concrete systems can be used to rapidly construct foundations$ 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
-
8/9/2019 Prefabricated Concrete
12/17
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$@> in heiht abo!e rade before additional
bracin is re(uired$
-
8/9/2019 Prefabricated Concrete
13/17
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
-
8/9/2019 Prefabricated Concrete
14/17
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
-
8/9/2019 Prefabricated Concrete
15/17
"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$
-
8/9/2019 Prefabricated Concrete
16/17
?anufacturin process
-
8/9/2019 Prefabricated Concrete
17/17
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