SECTION 03420 PRECAST PRESTRESSED CONCRETE SECTIONS

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Project Manual

03420
-
1





March 2008



Precast Prestressed Concrete Sections


SECTION 03420


PRECAST PRESTRESSED CONCRETE SECTIONS


PART
1

GENERAL


1.01

Description



Work Specified Herein and Elsewhere



A.

Work under this Section includes:


1.

Precast prestressed concrete
hollow core planks
.


2
.

All accessories, including rei
nforcements, inserts, attachment anchors
and plates, fastenings of all kinds and all other items as may be required
for complete installation of the precast prestressed concrete members.



B.

Related work specified elsewhere

1.

Cast
-
in
-
place concrete and

topping
-

Section 03300.

2.

Structural steel framing
-

Division 5.


3.

Met
al accessories embedded in cast
-
in
-
place concrete and masonry
-
Divisions 3 and 4.

4.

Roof and deck insulation
-

Section 07220.


5
.

Sealing of j
oints in precast concrete work
-

Sect
ion 07900.


1.02

Submittals


A.

All submittals shall be in accordance with Section 01300.


B.

Shop Drawings


Submit shop drawings indicating 28 day camber with all superimposed loading,
long term camber with superimpos
ed dead load only, shapes, cast
-
i
n items,
sections, jointing, setting plans, reinforcement, connection details, openings,
recesses and exposed surface finish to the E/A for approval prior to fabrication.
Each unit shall be identified by a standard mark at the time of manufacture to
facil
itate erection.


1.03

Applicable Publications


A.

American Concrete Institute (ACI)


ACI 211.1

Selecting Proportions for Concrete

ACI 318
-
77

Building Code Requirements for Reinforced Concrete


B.

American Society for Testing and Materials (ASTM)


A 41
6

Stress
-
relieved strand for Prestressed Concrete

C 192

Making and Curing Concrete Test Specimens in the Laboratory

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Project Manual

03420
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March 2008



Precast Prestressed Concrete Sections

C 33

Concrete Aggregate

C 150

Portland Cement

C 330

Lightweight Aggregates for Structural Concrete


C.

Prestressed Concrete Institute (PCI)



Design Handbook 1978 MNL
-
116



PCI Manual for Quality Control: Precast/Prestressed Concrete


1.0
4

Design


A.

Precast prestressed concrete structural units shall conform to the requirements
of ACI 318, except as otherwise indicated on the Drawings, an
d shall
have

the
size and configuration indicated on the Drawings, or equal.


B.

All units shall be capable of supporting the total design loads indicated on the
Drawings with provision for any additional construction loads and stresses at
openings and su
pports for work of other trades. All units shall be adequately
reinforced to resist all handling stresses.


C.

Precast prestressed units for wall construction shall be designed only for wind
forces and handling stresses in order to minimize additional ca
mber due to creep
of the concrete.


D.

Units shall be furnished with Underwriters Laboratory Fire Resistance Label for a
1
-
hour rating for double tees and a 2
-
hour rating for all other sections.


E.

Submit calculations on the design of all units, structu
ral steel headers, and cast
-
in
-
place concrete fillers, if any.


1.0
5

Tests


A.

General


All tests shall be performed in strict accordance with ASTM C31 and C39, by an
independent testing laboratory approved by E/A and at expense of the fabricator.
Failu
re to meet the strength requirements shall be cause for rejection. The
laboratory shall submit test reports directly to the E/A.


B.

Prestressing Steel


Certified test reports of ultimate strength and typical stress strain curves shall be
furnished by t
he steel manufacturer to the E/A.


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Project Manual

03420
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March 2008



Precast Prestressed Concrete Sections

C.

Compression Tests


Three compression test specimens shall be made for each days pour of each
class of concrete. The specimens shall be laboratory cured and tested in
accordance with ASTM C39 at 28 days; seven
-
day t
ests may be substituted for
28
-
day tests if the relation between the 7 and 28
-
day strengths of the concrete
has been established. Additional cylinders shall be made to determine strength
for transfer of prestress and shall be cured under the same conditio
ns as the
precast concrete. If high early strength concrete is used, specimens shall be
tested at 7 days.


D.

Air Content


If air entraining agents are used, tests shall be made at the same time that
specimens for compression tests are made. The air co
ntent of the concrete shall
be determined, by dir
ect measurement, using the volu
metric method in
accordance with ASTM C173.


PART
2

PRODUCTS


2.01

Cement


A.

Portland cement shall conform to ASTM C150, Type III.


B.

White portland cement for exposed p
recast architectural concrete shall conform
to ASTM C150, Type I.


C.

All cement used for exposed precast concrete shall be from one source.


2.02

Aggregate


A.

Concrete aggregate shall conform to ASTM C33. High strength haydite
aggregate may be used f
or precast slabs.


B.

Coarse aggregate for exposed architectural facing mixes shall be white quartz
selected and graded in size and color to match approved samples.


C.

Fine aggregate for exposed architectural facing mixes shall be manufactured
from the
coarse aggregate or from silica sand free of dust, silt or salts. Ordinary
concrete sand will not be permitted.


D.

All aggregates used for facing mixes shall be from one source.


2.03

Admixtures




A.

Admixtures, including air entrainment, may be used

at the discretion of the
precast concrete fabricator, and shall be approved by the E/A. An air entraining
agent, if used, shall be added at the mixer and shall conform to ASTM C260.
Admixtures containing chlorides, fluorides or nitrates shall not be use
d.


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Project Manual

03420
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March 2008



Precast Prestressed Concrete Sections

2.04

Reinforcement


A.

Prestressing steel shall be uncoated seven
-
wire, stress
-
relieved strand
conforming to ASTM A416 with a nominal ultimate strength of 270 ksi.


B.

High tensile stress
-
relieved wire shall conform to ASTM A421.


C.

Welded wire fa
bric shall conform to ASTM A185 and shall be flat sheets or mats,
not rolls.


D.

All billet steel reinforcement shall conform to ASTM A615, Grade 60.


E.

Dowel rods and transverse tie rods shall be SAE 10200R, ASTM A306, Grade
70
-
80.


2.05

Metal Accesso
ries


A.

Metal accessories including dovetail anchor slot inserts, anchors, dowels,
clamps, plates, clip angles, and other inserts shall be provided as required for
proper installation of the work. Unless otherwise indicated on the Drawings, the
metal ac
cessories shall be fabricated from galvanized steel or wrought iron
approved by the E/A. Weld areas and exposed surfaces of accessories shall be
primed for painting in accordance with Section 09900.


2.06

Concrete


A.

Concrete for precast prestressed co
ncrete

hollow

core planks

shall have a
minimum
compressive
strength of 5000 psi
and be machine extruded at zero
slump.




PART
3

EXECUTION


3.01

Fabrication



A.

Qualifications




The Contractor shall submit evidence to the E/A that the fabricator has h
ad a
satisfactory record with this type of work and that he has an adequate
prestressing plant meeting the standards of the Prestressed Concrete Institute.


B.

Holes



1.

Openings equal to or larger than 12 inches diameter or 12 inches square
shall be ca
st in by the unit manufacturer in accordance with approved
shop drawings. All other holes shall be cut by the trade requiring them
after locations are approved by the E/A. Reinforcement shall not be field
cut without the E/A's approval. Unsightly spalls

or chips from field cutting
shall be repaired.


2.

Unsightly spalls or chips from field cutting shall be repaired.

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Project Manual

03420
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March 2008



Precast Prestressed Concrete Sections


3.

Perimeter of rectangular openings shall be finished with 1 inch wood trim,
as required, to conceal cores within units and exposed edg
es around
openings. Trim to be painted as specified in Section 09900.



C.

Forms


1.

Construct forms and molds of materials that will produce precast units
with sharp risers, uniform in shape and texture, and dimensionally
accurate. Prestressing steel s
hall be placed in accordance with Drawings.
Do not use form materials having absorptive contact surfaces.


2.

Thoroughly clean form faces after each casting operation and repair
minor defects. A non
-
staining form
-
release agent may be used to coat
the fo
rms in order to facilitate stripping.


3.

Accurately position and cast all accessories into the units or provide
suitable recesses and anchors to receive accessories as required.


D.

Curing




The fabricated units shall be cured until
design
strength
is

reache
d

by any of the
following methods:


1.

Steam or hot water curing at maximum temperature not exceeding l65`F.
After placement of the concrete, prestressed members shall be held for a
minimum preset period of not less than 3 hours.



2.

Hot air com
bined with moisture.


3.

Continuous water curing.



E.

Tolerances




Deviation from dimensions shall be as outlined in PCI Manual 116.


F.

Steel Tendons


1.

Tendons shall be free of rust pitting. A light coating of rust is desirable,
but visible rust
pitting will be cause for rejection.


2.

Tendons shall be free of form oil.


3.

Pretensioning elongation and total stress as measured by gauge shall be
checked regularly and shall not vary more than 5%.


4.

Transfer of prestress to the concrete shall no
t be made until the concrete
strength has reached 3500 psi. Transfer of prestress may be by gradual
release of the tensioning jacks or by burning of strands, taking care to
prevent unsymmetrical stressing. Prior to transfer of prestress, forms
shall be l
oosened or removed to allow free movement of the casting.


G
.

Finish


Finish for precast units shall be Standard, except exposed surfaces shall have air
pockets and holes over 1/4 inch diameter filled with grout composed of one part
cement and 3 parts sa
nd. Color shall match the units. Offsets or fins over 1/8
inch shall be ground smooth.



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Project Manual

03420
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March 2008



Precast Prestressed Concrete Sections





3.02

Installation


A.

Handling


All members shall be transported directly to their permanent supports, if
practicable. If for convenience they are temporari
ly supported, calculations shall
be furnished showing that the temporary supports will not produce overstressing
of the member.


B.

Acceptance


Prior to installation of precast units remedy any defects or conditions that will
interfere with or prevent sa
tisfactory installation. Installation of units shall imply
acceptance of previous work.


C.

Welding


Welding for inserts and anchors shall be in accordance with AWS D
-
1.4
-
79,
"Reinforcing Steel Welding Code".


D.

Erection


1.

Precast prestressed units

shall be erected by the precast fabricator or in
accordance with his instructions.


2.

Provide cast
-
in
-
place concrete fillers or precast prestressed concrete
fillers where larger openings are provided than required by equipment.
Fillers shall be suffici
ently reinforced to carry the total design load and
shall be adequately anchored to supporting headers and adjacent units,
per approved shop drawings. Surfaces of fillers exposed to view shall be
finished to match adjacent unit surfaces.


3.

Installation
shall comply with the requirements for the UL fire ratings
specified.


4.

Sequence of erection shall be outlined prior to start of erection and strictly
adhered to. Base lines and elevations shall be established by the
Contractor prior to erection.


5.

Anchorage of prestressed sections shall be as indicated on Drawings and
approved shop drawings.


6.

Obtain permission from the E/A for all openings not shown on approved
shop drawings, except small diameter openings that do not cut
reinforcement.


7.

Spe
cial care shall be given to the alignment of units. Joints shall not be
grouted until approved by the E/A. Camber adjustments for adjacent
units shall be within the limits outlined in PCI Manual 116. Joints between
all roof units shall be grouted to a sl
ope not to exceed 1/8 inch per foot.


8.

Shear keys shall be grouted with a very dry mortar of
3
:1 sand and
portland cement, tamped into and completely filling the keys.


9.

Seal all exposed joints in accordance with Section 07900.

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Project Manual

03420
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March 2008



Precast Prestressed Concrete Sections




3.03

Cleaning


A.

After all precast prestressed concrete is in place and the sealing operations have
been performed, surfaces exposed to view shall be scrubbed with mild soap and
water using fiber brushes and then thoroughly rinsed with clean water. Protect
adjacent surfa
ces as required.


B.

Upon completion of precast prestressed concrete work, leave exposed surfaces
clean and free of pointing and cleaning compounds and ready for finishing, if any.


3.04

Water Repellent Treatment


A.

After cleaning and the surfaces are
thoroughly dry, surfaces exposed to weather
shall be treated with silicone water repellent in accordance with Section 03300.




END OF SECTION