STANDARD SPECIFICATIONS FOR CONSTRUCTION OF ROADS AND BRIDGES ON FEDERAL HIGHWAY PROJECTS (FP-14) - page 11

 

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STANDARD SPECIFICATIONS FOR CONSTRUCTION OF ROADS AND BRIDGES ON FEDERAL HIGHWAY PROJECTS (FP-14) - page 11

 

 

Section 551
In addition, do not allow the pile stresses resulting from the wave equation analysis to exceed the
values at which pile damage is impending. The point of impending damage is defined for steel,
concrete, and timber piles as follows.
(a) Steel piles. Limit the compressive driving stress to 90 percent of the yield strength of the
pile material.
(b) Concrete piles. Limit the tensile (TS) and compressive (CS) driving stresses to:
TS 3fc'1/2 + EPV for US Customary
TS 0.25fc'1/2 + EPV for Metric
CS 0.85fc' - EPV for US Customary
CS 0.85fc' - EPV for Metric
where:
fc
= The 28-day design compressive strength of the concrete in pounds per square
inch (megapascals)
EPV= The effective prestress value in pounds per square inch (megapascals)
(c) Timber piles. Limit the compressive driving stress to:
σdr = φda(FCO) where:
σdr = limiting driving stress (ksi or kilonewtons)
φda = resistance factor, drivability analysis
FCO
= base resistance of wood in compression parallel to the grain
(ksi or
kilonewtons)
(2) Minimum hammer energy. The energy of the driving equipment submitted for approval, as
rated by the manufacturer, will be determined by a wave equation analysis.
(c) Driving appurtenances.
(1) Hammer cushion. Equip impact pile-driving equipment, except gravity hammers, with a
suitable thickness of hammer cushion material to prevent damage to the hammer or pile and to
ensure uniform driving behavior. Fabricate hammer cushions from durable, manufactured
material according to the hammer manufacturer’s recommendations. Do not use wood, wire
rope, or asbestos hammer cushions. Place a striker plate, as recommended by the hammer
manufacturer, on the hammer cushion to ensure uniform compression of the cushion material.
Inspect the hammer cushion in the presence of the CO when beginning pile driving at each
structure or after each 100 hours of pile driving, whichever is less. Replace the cushion when its
thickness is reduced by more than 25 percent of its original thickness;
(2) Pile drive head. Provide adequate drive heads for impact hammers. Provide appropriate
drive heads, mandrels, or other devices for special piles according to the manufacturer’s
recommendations. Align the drive head axially with the hammer and pile. Fit the drive head
around the pile head so that transfer of torsional forces is prevented during driving and proper
alignment of hammer and pile is maintained;
385
Section 551
(3) Leads. Support piles in line and position with leads while driving. Construct pile driver leads
to allow freedom of movement of the hammer while maintaining axial alignment of the hammer
and the pile. Do not use swinging leads unless permitted in writing or specified in the contract.
When swinging leads are permitted fit swinging leads with a pile gate at the bottom of the leads
and in the case of battered piles, fit with a horizontal brace between the crane and the leads.
Adequately embed leads in the ground or constrain the pile in a structural frame (template) to
maintain proper alignment. Provide leads of sufficient length that do not require a follower, but
will permit proper alignment of battered piles;
(4) Followers. Do not use followers unless approved. When followers are permitted, drive the
first pile in each bent or substructure unit and every tenth pile thereafter, full length without a
follower, to verify that adequate pile embedment is being attained to develop the required
nominal capacity. Provide a follower of such material and dimensions that will permit the piles
to be driven to the required penetration. Hold and maintain follower and pile in proper alignment
during driving;
(5) Jetting. Do not use jetting unless approved. Provide jetting equipment with sufficient
capacity to deliver a consistent pressure equivalent to at least 100 pounds per square inch
(700 kilopascals) at two ¾-inch (19-millimeter) jet nozzles. Jet so as not to affect the lateral
stability of the final in-place pile. Remove jet pipes when the pile tip is at least
5 feet
(1.5 meters) above the prescribed tip elevation, and drive the pile to the required nominal
capacity with an impact hammer. Control, treat if necessary, and dispose of jet water in an
approved manner;
(6) Pile cushion. For concrete piles, use a new pile cushion to protect the head of each pile. Cut
the pile cushion at least 4 inches (100 millimeters) thick and to match the cross-section of the
pile top. Replace the pile cushion if it is compressed more than one-half its original thickness or
it begins to burn. For steel and timber piles, protect each pile with an approved driving cap.
Enclose timber piles with approved collars or bands to prevent splitting or brooming. Replace
caps when damaged. Do not reuse cushions or caps; and
(7) Pile shoes. When specified, provide shoes to protect the pile-tip from damage during driving.
Fabricate shoes to snugly fit the pile tip. For concrete piles, attach the shoe to the pile using
dowels or other approved methods. For steel piles, design and fit the shoe to the steel shape and
weld the shoe to the pile so as not to stress the web or the flange. For timber piles, carefully
shape the tip to secure an even uniform bearing for the pile shoe. Treat holes, cuts, or caps in
treated timber piles with two-brush applications of creosote-coal tar solution according to
AWPA.
551.06 Pile Lengths. Furnish piles with sufficient length to obtain the required resistance and to extend
into the pile cap or footing as indicated in the plans. In addition, increase the length to provide fresh
heading and to provide for the Contractor's method of operation. When test piles are required, furnish piles
in the lengths determined by the test piles.
551.07 Test Piles. Install test piles when specified in the contract.
Place the piles designated as dynamic load test piles in a horizontal position and not in contact with other
piles. Drill holes for mounting instruments near the head of the pile. Mount the instruments after the pile is
in leads and take wave speed measurements. Provide at least a 48- by 48-inch (1200- by 1200-millimeter)
rigid platform with a 42-inch (1050-millimeter) safety rail that can be raised to the top of the pile.
386
Section 551
Excavate the ground at the site of each test pile or production pile to the elevation of the bottom of the
footing before the pile is driven. Furnish test piles longer than the estimated length of production piles.
Drive test piles with the same equipment as the production piles.
Drive test piles to the required nominal capacity at the estimated tip elevation. Allow test piles that do not
attain the required nominal capacity at the estimated tip elevation to set up for 24 hours before re-driving.
Warm the hammer before re-driving begins by applying at least 20 blows to another pile. If the required
nominal capacity is not attained on re-driving; drive a portion or the remaining test pile length and repeat
the set up and re-drive procedure as directed. Splice and continue driving until the required nominal pile
capacity is obtained.
Conform to the requirements for production piles when test piles are to be used in the completed structure.
Remove test piles not incorporated in the completed structure to at least 24 inches (600 millimeters) below
finished grade.
551.08 Driven Pile Capacity. Drive piles to the specified penetration and to the depth necessary to obtain
the required nominal pile capacity. Splice piles not obtaining the required nominal capacity at the ordered
length, and drive with an impact hammer until the required nominal pile capacity is achieved.
Use the wave equation to determine nominal pile capacity of the in-place pile.
(a) Wave equation. Adequate penetration will be considered to be obtained when the specified wave
equation resistance criteria is achieved within 5 feet (1.5 meters) of the designated tip elevation. Drive
piles that do not achieve the specified resistance within these limits to a penetration determined by the
CO.
(b) Dynamic formula. Drive the piles to a penetration necessary to obtain the nominal pile capacity
according to the FHWA Gates Formula:
R
=1.75
E log
(10N )
100
ndr
d
10
b
(US Customary)
R
=
7
E log
(10N )
550
ndr
d
10
b
(Metric)
where:
Rndr
= Nominal pile resistance measured during pile driving in kips (kilonewtons)
Ed
=Developed hammer energy. This is the kinetic energy in the ram at impact
for a given blow. If ram velocity is not measured, it may be assumed equal
to the potential energy of the ram at the height of the stroke, taken as the
ram mass times the stroke (foot-pounds or joules)
log10(10Nb)
= Logarithm to the base 10 of the quantity 10 multiplied by N
Nb
= Number of hammer blows per inch (25 millimeters) at final penetration
387
Section 551
Determine the in-place nominal capacity of jetted piles based on impact hammer blow counts
(dynamic formula) after the jet pipes have been removed. After the pile penetration length necessary
to produce the required nominal pile capacity has been determined by impact hammer blow count,
install the remaining piles in each group or in each substructure unit to similar depths with similar
methods. Confirm the required nominal pile capacity has been achieved by using the dynamic
formula.
551.09 Preboring. Use auguring, wet rotary drilling, or other approved methods of preboring.
Prebore the pile hole to natural ground in compacted embankments more than 5 feet (1.5 meters) deep.
In natural ground, preboring may extend to the surface of the rock or hardpan for piles end-bearing on rock
or hardpan. Seat the pile into the end-bearing strata.
Stop preboring at least 5 feet (1.5 meters) above the estimated pile tip elevation and drive the pile with an
impact hammer to a penetration which achieves the required nominal pile capacity for piles not
end-bearing on rock or hardpan. Prebore holes smaller than the diameter or diagonal of the pile
cross-section while allowing penetration of the pile to the specified depth.
Increase the hole diameter to the least dimension adequate for pile installation if the subsurface
obstructions such as boulders or rock layers are encountered. Fill remaining void space around the pile
with sand or other approved material after driving is complete. Do not use a punch or a spud instead of
preboring.
Do not impair the capacity of existing piles or the safety or condition of adjacent structures. If preboring
disturbs the capacity of previously installed piles or structures, restore the required nominal capacity of
piles and structures by approved methods.
551.10 Preparation and Driving. Perform the work under Section 208. Make the heads of piles plane and
perpendicular to the longitudinal axis of the pile. Coordinate pile driving to prevent damage to other parts
of the completed work.
Drive pile heads to within 3 inches (75 millimeters) of plan location at cutoff elevation for bent caps
supported by piles and to within 6 inches (150 millimeters) of plan location from piles capped below final
grade. Locate and drive piles at least 4 inches (100 millimeters) from any edge of the cap. Drive piles so
that the axial alignment is within ¼ inch per foot (20 millimeters per meter) along the longitudinal axis of
the required alignment. The CO may stop driving to check the pile alignment. Check alignment before the
last 5 feet (1.5 meters) are driven for piles that cannot be internally inspected after installation. Do not pull
laterally on piles or splice to correct misalignment. Do not splice a properly aligned section on a
misaligned pile.
Place individual piles in pile groups either starting from the center of the group and proceeding outward in
both directions or starting at the outside row and proceeding progressively across the group.
Correct piles driven improperly, driven out of proper location, misaligned, or driven below the designated
cutoff elevation in an approved manner. Replace piles damaged during handling or driving. Obtain
approval for the proposed methods of correcting or repairing deficiencies.
388
Section 551
(a) Timber piles. Do not use piles with checks wider than ½ inch (13 millimeters). Drive treated
timber piles within 6 months after treatment. Handle and care for pressure-treated piles according to
AWPA, Standard M 4 Standard For The Care Of Preservative-Treated Wood Products.
(b) Steel piles. Furnish full-length, un-spliced piles for lengths up to 60 feet (18 meters). If splices are
required in the first pile driven and it is anticipated that subsequent piles will also require splices, place
the splices in lower third of the pile. Splice lengths less than 10 feet (3 meters) are not permitted and
only 2 splices per pile are allowed.
Load, transport, unload, store, and handle steel piles so the metal is kept clean and without damage. Do
not use piles that exceed the camber and sweep permitted by allowable mill tolerance. Steel piles
damaged during installation are unacceptable unless the minimum tip elevation is obtained and load
tests show the bearing capacity is 100 percent of the required nominal. Perform tests on damaged piles
at no cost to the Government. If driving points are required, weld driving points to steel piles according
to AASHTO/AWS, Structural Welding Code - Steel D1.1 (D1.1M) or AWS, Bridge Welding Code
D1.5 (D1.5M) as applicable.
(c) Precast and prestressed concrete piles. Support concrete piles during lifting or moving at the
points shown in the plans. Provide support at the quarter points if not specified. Furnish slings or other
equipment when raising or transporting concrete piles to avoid bending the pile or breaking edges.
Reject concrete piles with reduced strength caused by external defects such as spalls, cracks, or
internal defects such as cavities revealed with non-destructive testing.
(d) Concrete-filled pipe or steel shell piles. Furnish and handle the steel shells or pipes according to
Subsection 551.10(b). Cutting shoes for shells or pipes may be inside or outside the shell. Use high-
carbon structural steel with a machined ledge for shell bearing or cast steel with a ledge designed for
attachment with a simple weld.
Drive pile shells or pipes for a substructure unit before placing concrete in the shells or pipes when
practical. Do not drive pile shells or pipes within 15 feet (5 meters) of concrete-filled pile shell or pipe
until the concrete has cured for at least 7 days or 3 days if using high-early-strength concrete. Do not
drive pile shell or pipe after it is filled with concrete.
Remove and replace shells that are determined to be unacceptable for use due to breaks, bends, or
kinks.
551.11 Splices. Align and connect pile sections so the axis of the spliced pile is straight.
(a) Steel piles. Use welders certified for structural welding.
Make surfaces to be welded smooth, uniform, and without loose scale, slag, grease, or other material
that prevents proper welding. Steel may be oxygen cut. Carbon-arc gouging, chipping, or grinding may
be used for joint preparation.
389
Section 551
Weld according to AASHTO/AWS, Structural Welding Code - Steel D1.1 (D1.1M) or AWS, Bridge
Welding Code D1.5 (D1.5M). Weld the entire pile cross-section using prequalified AWS groove weld
butt joints. Weld so there is no visual evidence of cracks, lack of fusion, undercutting, excessive
piping, porosity, or inadequate size. Do not use manufactured splices unless approved in writing or
shown in the plans. Manufactured splices may be used in place of full penetration groove butt welds if
the Contractor can prove they can develop the full strength of the pile in compression, tension and
bending.
(b) Concrete pile splices. Use dowels or other acceptable mechanical means to splice precast concrete
or precast prestressed concrete piles. Submit drawings of proposed splices for approval.
If dowels are used, cast the dowels into the tip end of the following pile with corresponding holes at
the butt end of the driven pile. Serrate the holes to provide a mechanical bond. Separate the ends of the
piles by at least ½ inch (13 millimeters). Clean surfaces and dowel holes. Grout the dowels in place
and allow the grout to cure. Enclose the gap with forms and inject a bonding agent capable of
withstanding the impact and driving forces and having the same compressive strength as the pile.
Follow the manufacturer’s recommendations regarding the use and curing of grouting and bonding
products.
Attach manufactured splices to the concrete piles as recommended by the manufacturer. Ensure the
splice develops strengths in compression, tension, and bending equal to or exceeding the strength of
the pile being spliced.
(c) Concrete pile extensions.
(1) Precast concrete piles. Extend precast concrete piles by removing the concrete at the end of
the pile and leaving 40 diameters of reinforcement steel exposed. Remove the concrete to
produce a face perpendicular to the axis of the pile. Securely fasten reinforcement of the same
size as that used in the pile to the projecting reinforcing steel. Form the extension to prevent
leakage along the pile.
Immediately before placing concrete, wet the top of the pile thoroughly and cover with a thin
coating of neat cement, re-tempered mortar, or other suitable bonding material. Place concrete of
the same mix design and quality as that used in the pile. Keep forms in place for not less than
7 days after the concrete has been placed. Cure and finish according to Section 552.
(2) Prestressed piles. Extend prestressed precast piles according to Subsection
551.11(b).
Include reinforcement bars in the pile head for splicing to the extension bars. Do not drive
extended prestressed precast piles.
(d) Timber piles. Do not splice timber piles.
551.12 Heaved Piles. Check for pile heave during the driving operation. Take level readings immediately
after each pile is driven and again after piles within a radius of 15 feet (5 meters) are driven. Re-drive piles
that heave more than ½ inch (13 millimeters) for end-bearing piles or 1½ inches (38 millimeters) for
friction piles. Re-drive to the specified resistance or penetration.
551.13 Pile Load Tests. Pile load tests are not required unless specified.
(a) Dynamic load test. Furnish equipment and perform dynamic load tests according to ASTM D4945
under the supervision of the CO. Mount the instruments according to Subsection 551.07.
390
Section 551
Drive the pile to the depth at which the dynamic test equipment indicates that the required nominal pile
capacity is achieved. If necessary to maintain stresses in the pile below the values in Subsection
551.03(b)(1), reduce the driving energy transmitted to the pile by using additional cushions or reducing
the energy output of the hammer. Realign the driving system if nonaxial driving is indicated.
At least 24 hours after the initial driving, re-drive each dynamic load test pile with instrumentation
attached. Warm the hammer before re-driving by applying at least 20 blows to another pile. Re-drive
the dynamic load test pile for a maximum penetration of 3 inches (75 millimeters), a maximum of
20 blows, or to practical driving refusal, whichever occurs first. Practical driving refusal is defined as
12 blows per inch (15 blows per 25 millimeters) for steel piles, 10 blows per inch (8 blows per
25 millimeters) for concrete piles, and 5 blows per inch (5 blows per 25 millimeters) for timber piles.
Verify the assumptions used in the initial wave equation analysis submitted according to Subsection
551.03(b) using signal matching analysis. Analyze one blow from the original driving and one blow
from the re-driving for each pile tested.
Perform additional wave equation analyses with adjustments based on the signal matching analysis
results. Provide a graph showing blow count versus nominal capacity. Provide a blow count versus
stroke graph for the nominal capacity of open-ended diesel hammers. Provide the driving stresses,
transferred energy, and pile capacity as a function of depth for each dynamic load test.
Based on the results of the dynamic load testing, signal matching analyses, and wave equation
analyses, the order list and production driving criteria may be approved and the required cut-off
elevations provided, or additional test piles and load testing may be specified. This information will be
provided within 7 days after receipt of the order list and required test data for the test piles driven.
(b) Static load tests. Perform static load tests according to ASTM D1143 using the quick load test
method, except as modified herein. Submit drawings of the proposed loading apparatus for approval
according to the following:
(1) Have a professional engineer prepare the drawings;
(2) Furnish a loading system capable of applying 150 percent of the nominal pile capacity or
1,000 tons (9000 kilonewtons), whichever is less; and
(3) Construct the apparatus to allow increments of load to be placed gradually without causing
vibration to the test pile.
Perform test at least 5 days after test pile was driven unless approved by the CO. Drive tension piles at
the location of permanent piles when feasible if tension (anchor) piles are required. Do not use timber
or tapered piles installed in permanent locations as tension piles. Take the test to plunging failure or the
capacity of the loading system, whichever occurs first.
The nominal bearing resistance is defined as 50 percent of the failure load. The failure load is defined
as follows:
• For piles 24 inches (600 millimeters) or less in diameter, length of side for square piles or
diagonal width, the load that produces a settlement at failure of the pile head equal to:
Sf = S + (0.15 + 0.008D
)
(U.S. Customary)
391
Section 551
Sf = S + (3.8 + 0.008D
)
(Metric)
• For piles greater than 24 inches (600 millimeters) in diameter, length of side for square piles or
diagonal width:
D
S
f
=
S
+
30
where:
Sf
= Settlement at failure in inches (millimeters)
D = Pile diameter or diagonal width in inches (millimeters)
S
= Elastic deformation of pile in inches (millimeters)
Determine top elevation of the test pile immediately after driving and again just before load testing to
check for heave. Wait at least
3 days between the driving of anchor or load test piles and the
commencement of the load test. Before testing, re-drive or jack to the original elevation piles that heaves
more than ¼ inch (6 millimeters).
After completion of the load testing, remove or cut off test or anchor piling not a part of the finished
structure at least 24 inches (600 millimeters) below either the bottom of footing or the finished ground
elevation.
Based on the results of the static load testing, the order list and production driving criteria may be
approved and the required cut-off elevations provided or additional load tests may be specified. This
information will be provided within 7 days after receipt of the order list and required test data for the test
piles driven.
551.14 Pile Cutoffs. Cut off the tops of permanent piles and pile casings at the required elevation. Cut off
the piles clean and straight parallel to the bottom face of the structural member in which they are
embedded. Dispose of cutoff lengths according to Subsection 203.05(a).
Treat the heads of treated timber piles which are not embedded in concrete by one of the following
methods:
(a) Reduce the moisture content of the wood to no more than 25 percent with no free moisture on the
surface. Brush apply one application of creosote-coal tar solution as required in AWPA Standards.
Build up a protective cap by applying alternate layers of loosely woven fabric and hot asphalt or tar,
similar to membrane waterproofing, using three layers of asphalt or tar and two layers of fabric. Use
fabric at least 6 inches (150 millimeters) wider in each direction than the diameter of the pile. Turn
the fabric down over the pile and secure the edges by binding with two turns of No. 10
(3-millimeter) galvanized wire. Apply a final layer of asphalt or tar to cover the wire. Neatly trim the
fabric below the wires.
(b) Cover the sawed surface with three applications of a hot mixture of 60 percent creosote and
40 percent roofing pitch, or thoroughly brush coat with three applications of hot creosote and cover
with hot roofing pitch. Place a covering of galvanized sheet metal over the coating and bend down
over the sides of each pile.
392
Section 551
551.15 Unsatisfactory Piles. Correct unsatisfactory piles by an approved method. Methods of correcting
unsatisfactory piles may include one or more of the following:
(a) Use of the pile at a reduced capacity;
(b) Install additional piles;
(c) Repair damaged piles; and
(d) Replace damaged piles.
551.16 Placing Concrete in Steel Shell or Pipe Piles. Clean the inside of shells and pipes by removing
loose material after driving. Keep the shell or pipe substantially water tight. Remove water before placing
concrete or place the concrete using a tremie when water is present in the pile. Provide suitable equipment
for inspecting the entire inside surface of the driven shell or pipe just before placing concrete.
(a) Reinforcing steel. Make the spacing between adjacent cage elements at least five times the
maximum size of aggregate in the concrete when reinforcing steel is required.
Securely tie concrete spacers or other approved spacers at fifth points around the perimeter of the
reinforcing steel cage. Install spacers at intervals not to exceed 10 feet (3 meters) measured along the
length of the cage.
Place the reinforcement cage into the driven shell or pipe when the concrete reaches the planned
bottom elevation of the reinforcement. Support the reinforcement so it remains within 2 inches
(50 millimeters) of the required vertical location. Support the cage from the top until the concrete
reaches the top of the pile.
(b) Concrete. Construct concrete according to Section 552. Place concrete in one continuous operation
from the bottom to the top of the pile. Consolidate the top 10 feet (3 meters) of the concrete pile using
approved vibratory equipment before the initial concrete set.
551.17 Acceptance. Pile material will be evaluated under Subsections 106.02 and 106.03.
Furnish production certifications with each shipment of the following:
(a) Concrete piles;
(b) Sheet piles, steel H-piles, steel shells, and steel pipes; and
(c) Treated timber piles. Stamp each pile with an identification mark and date of inspection.
Driving piles and related work will be evaluated under Subsections 106.02 and 106.04.
Concrete for steel shells or pipe piles will be evaluated under Section 552.
Reinforcing steel for steel shells or pipe piles will be evaluated under Section 554.
393
Section 551
Measurement
551.18 Measure the Section 551 pay items listed in the bid schedule according to Subsection 109.02 and
the following as applicable:
When measuring piles by the linear foot (meter), measure the length of pile from the cutoff elevation to the
tip.
Measure splices required to drive piles deeper than the estimated tip elevation.
Payment
551.19 The accepted quantities will be paid at the contract price per unit of measurement for the Section
551 pay items listed in the bid schedule. Payment will be full compensation for the work prescribed in this
Section. See Subsection 109.05.
394
Section 552
Section 552. — STRUCTURAL CONCRETE
Description
552.01 This work consists of furnishing, placing, finishing, and curing concrete in bridges, culverts, and
other structures.
Structural concrete class is designated in the plans according to Table 552-1.
Material
552.02 Conform to the following Section and Subsections:
Coarse aggregate for concrete
703.02
Color coating
725.15
Concrete curing material and admixtures
711
Elastomeric bearing (pads)
717.10(a)
Epoxy resin adhesives
725.18
Fine aggregate for concrete
703.01
Hydraulic cement
701.01
Non-shrink grout
725.13(b)
Pozzolans
725.04
Preformed polychloroprene elastomeric joint seal for bridges
712.01(g)
Reinforcing fibers
725.17
Sealants, fillers, and seals
712.01
Water
725.01(a)
Construction Requirements
552.03 Composition (Concrete Mix Design). Design and produce concrete mixtures that conform to
Tables 552-1, 552-2, and 552-3 as required for the class specified. Determine design strength values
according to Chapter
5 of ACI
318, Building Code Requirements for Structural Concrete and
Commentary.
395
Section 552
Table 552-1
Composition of Concrete
Class
Minimum
Maximum
Coarse Aggregate
of
Compressive Strength
Water/
Size Number
Concrete
@ 28-Days, f’c,
Cementitious
AASHTO M 43 (1)
psi (MPa)
Material
Ratio
A
4500 (31.0)
0.45
5, 56, 57
A(AE)
4500 (31.0)
0.45
5, 56, 57
C
4500 (31.0)
0.45
7, 78
C(AE)
4500 (31.0)
0.45
7, 78
D(AE) (2)
5000 (34.5)
0.40
5, 56, 57
P (Prestressed) (3)
See plans
-
6,7,67,68,78
P(AE) (3)
See plans
-
6,7,67,68,78
S (Seal)
-
0.54
5, 56, 57
(1) Meet the processing requirements of AASHTO M 43, Table 1 - Standard Sizes of Processed
Aggregate.
(2) The maximum water-soluble chloride ion (Cl-) content is 0.15 percent by mass of cement. Determine
the water-soluble chloride ion content of concrete made with mix ingredients at an age between 28 and
48 days according to ASTM C1218. Submit test results with the concrete mix design for approval.
(3) The maximum water-soluble chloride ion (Cl-) content is 0.06 percent by mass of cement. Determine
the water-soluble chloride ion content of concrete made with mix ingredients at an age between 28 and
48 days according to ASTM C1218. Submit test results with the concrete mix design for approval.
Table 552-2
Air Content for Air Entrained Concrete(1)
Nominal Maximum
Minimum
Maximum
Aggregate Size (2)
Air Content (3) (%)
Air Content (3) (%)
1½ inch (37.5 mm)
4.0
7.0
1 inch (25 mm)
4.5
7.5
¾ inch (19 mm)
4.5
7.5
½ inch (12.5 mm)
5.5
8.5
(1) The minimum air content values in the table may be reduced by up to 1.0 percent for concrete
with f’c greater than 5000 pounds per square inch (34.5 megapascals).
(2) Meet the requirements of AASHTO M 43, Table 1 - Standard Sizes of Processed Aggregate.
(3) For P(AE) concrete, reduce the as-delivered minimum air content by 1.0 percent and use a
maximum air content of 6.0 percent.
396
Section 552
Table 552-3
Cementitious Material Requirements for Concrete
Maximum Percent of Total
Cementitious Material
Cementitious Material by
Mass
Fly ash or other pozzolans, AASHTO M 295
25
Slag, AASHTO M 302
50
Silica fume, AASHTO M 307
10
Total fly ash or other pozzolans, slag, and silica fume
50 (1)
Total fly ash or other pozzolans and silica fume
35 (1)
(1) Limit fly ash or other pozzolans to no more than 25 percent of the total mass of cementitious material and
limit silica fume to no more than 10 percent of the total mass of cementitious material.
Submit concrete mix designs on FHWA Form 1608, 552 Structural Concrete Mix Design Submittal.
Verify mixture design with trial mixes prepared according to ACI 318 from proposed sources or with
previous concrete production data for the mixture design submitted from proposed sources. Submit written
concrete mix designs for approval at least 36 days before production. Include the following in each mix
design submittal:
(a) Project identification;
(b) Name and address of Contractor and concrete producer;
(c) Mix design designation;
(d) Class of concrete and intended use;
(e) Material proportions;
(f) Name and location of material sources for aggregate, cement, admixtures, and water;
(g) Type of cement and other cementitious material if used. Fly ash, ground granulated blast-furnace
slag, or silica fume may partially replace cement in the mix. Follow the cement replacement limits in
Table 552-3;
(h) Cement content in pounds per cubic yard (kilograms per cubic meter) of concrete;
(i) The saturated surface dry batch mass of the coarse and fine aggregate in pounds per cubic yard
(kilograms per cubic meter) of concrete;
(j) Water content in pounds per cubic yard (kilograms per cubic meter) of concrete;
(k) Water/cementitious material ratio. The water/cementitious material ratio for modified concrete is
the ratio of the mass of water to the combined masses of hydraulic cement and cement substitute;
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Section 552
(l) Dosage of admixtures. Provide a qualified person from the admixture manufacturer to help establish
the proper dosage when requested by the CO. Do not mix chemical admixtures together in a mix
unless they are compatible. Furnish supporting documentation of compatibility from the
manufacturers.
(1) Air-entraining admixtures. Entrained air may be obtained with either air-entraining
hydraulic cement or air-entraining admixture.
(2) Set accelerating admixtures. Do not use chloride accelerators. Do not use set accelerating
admixtures in prestressed concrete applications.
(3) Hydration stabilizing admixtures. Hydration stabilizing admixtures may be used to extend
the allowable delivery time for concrete. Base the dosage on the time needed to delay the initial
set of the concrete for delivery and discharge on the job. Include the design discharge time limit
in the dosage submittal. The maximum allowable design discharge time is 3½ hours;
(m) Fine and coarse aggregate quality;
(n) Sieve analysis of fine and coarse aggregate;
(o) Absorption of fine and coarse aggregate;
(p) Bulk specific gravity (dry and saturated surface dry) of fine and coarse aggregate;
(q) Dry rodded density of coarse aggregate in pounds per cubic foot (kilograms per cubic meter.);
(r) Fineness modulus (FM) of fine aggregate;
(s) Material certifications for cementitious material, admixtures, and aggregate;
(t) Target values for concrete slump with and without high-range water reducers;
(u) Target values for concrete air content. Include the proposed range of air content for concrete to be
incorporated into the work. Describe the methods by which air content will be monitored and
controlled;
(v) Concrete density;
(w) Specified design strength (f’c) and required average strength (f’cr) for the concrete mixture at
28 days as determined by the process described in Chapter 5 of ACI 318. This process and associated
calculations are outlined on FHWA Form 1608, pages 4 and 5. Pending 28-day strength results, a mix
design may be approved on the basis that 7-day compressive strength results meet or exceed 85 percent
of the required average strength (f’cr) at 28 days;
(x) Compressive strengths test results at 7 and 28 days according to Table 552-9, note (3); and
(y) Material samples if requested.
Do not begin production until the mix design is approved by the CO.
Furnish a new mix design for approval if there is a change in a source of material or when the fineness
modulus of the fine aggregate changes by more than 0.20.
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Section 552
552.04 Handling and Storing Material. Handle and store material in a manner that prevents segregation,
contamination, or other harmful effects. Do not use cement and fly ash containing evidence of moisture
contamination. Store and handle aggregate in a manner that ensures uniform moisture content at the time
of batching.
552.05 Measuring Material. Batch the concrete according to the approved mix design and the following
tolerances:
(a) Cement
±1 percent
(b) Water
±1 percent
(c) Aggregate
±2 percent
(d) Additive
±3 percent
552.06 Batching Plant, Mixers, and Agitators. Use a batching plant, mixer, and agitator conforming to
AASHTO M 157.
552.07 Mixing. Mix the concrete in a central-mix plant or in truck mixers. Operate equipment within
manufacturer’s recommended capacity. Produce concrete of uniform consistency.
(a) Central-mix plant. Dispense liquid admixtures through a controlled flowmeter. Use dispensers
with sufficient capacity to measure, at one time, the full quantity of admixture required for each batch.
If more than one admixture is used, dispense each with separate equipment.
Charge the coarse aggregate, one-third of the water, and all air-entraining admixture into the mixer
first, then add remainder of the material.
Mix for at least 50 seconds. Begin mixing time after all cement and aggregate are in the drum. Add the
remaining water during the first quarter of the mixing time. Add 4 seconds to the mixing time if timing
starts the instant the skip reaches its maximum raised position. Transfer time in multiple-drum mixers
is included in mixing time. Mixing time ends when the discharge chute opens.
Remove the contents of an individual mixer before a succeeding batch is charged into the drum.
(b) Truck mixer. Do not use mixers with blades worn 1 inch (25 millimeters) or more below the
original manufactured height. Do not use mixers and agitators with accumulated hard concrete or
mortar in the mixing drum.
Add admixtures to the mix water before or during mixing.
Charge the batch into the drum so a portion of the mixing water enters before the cement.
Mix each batch of concrete according to AASHTO M 157.
552.08 Delivery. Produce and deliver concrete to permit a continuous placement with no concrete
achieving initial set before the remaining concrete being placed adjacent to it. Deliver, handle, and place
concrete so as to minimize rehandling of the concrete and prevent damage to the structure.
Do not place concrete that has developed an initial set. Do not re-temper concrete by adding water.
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Section 552
If a hydration stabilizing admixture is approved for use in the concrete mix, deliver and place the concrete
within the approved design discharge time limit. Limit the slump loss to no more than
2 inches
(50 millimeters) during the stabilization period. An approved and compatible hydration activator may be
used at the discharge site to ensure proper placement and testing.
(a) Truck mixer/agitator. Use the agitating speed for rotation after mixing. When a truck mixer or
truck agitator is used to transport concrete that is completely mixed in a stationary central construction
mixer, mix during transportation at manufacturer’s recommended agitating speed. Do not exceed
100 total revolutions at mixing speed, including both initial mixing and remixing.
If the concrete has not obtained an initial set, water and admixtures in the approved mix design may be
added one time at the project to obtain the required slump or air content. Limit the total of water in the
mix so as not to exceed the maximum water/cementitious material ratio of the approved mix design.
Remix the concrete and added water or admixtures with 30 revolutions at mixing speed. After the
initial introduction of mixing water to cement or cement to aggregates, complete the remixing within
the time specified in Table 552-4. After the beginning of the addition of the cement, complete the
discharge of the concrete within the time specified in Table 552-5.
Table 552-4
Concrete Remixing and Discharge Time Limits
Cement Type (1)
Admixtures
Remixing
Discharge
Time Limit
Time Limit
(hour)
(hour)
Type I, IA, II, IIA, V, or approved
None
0.75
1.00
blended hydraulic cement
AASHTO
Type I, IA, II, IIA, V, or approved
M 194,
1.25
1.50
blended hydraulic cement
Type B, D, or G
Approved design
Type I, IA, II, IIA, V, or approved
Hydration
discharge
3.00
blended hydraulic cement
stabilizer
time limit,
3.50 maximum
Type III
None
0.50
0.75
AASHTO
Type III
M 194,
1.00
1.25
Type B, D, or G
(1) AASHTO M 85 or AASHTO M 240 as applicable.
(b) Non-agitating equipment. Non-agitating equipment may be used to deliver concrete
if
the
concrete discharge is completed within 20 minutes from the beginning of the addition of the cement to
the mixing drum. Use equipment with smooth, mortar tight, metal containers capable of discharging
the concrete at a controlled rate without segregation. Provide covers when needed for protection.
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Section 552
552.09 Quality Control of Mix. Submit and follow a quality control plan according to Sections 153 and
154 as applicable and the following:
(a) Mixing. Designate a certified concrete technician at the mixing plant to be responsible for the
mixing operations and quality control including:
(1) Proper storage and handling of components of the mix;
(2) Proper maintenance and cleanliness of plant, trucks, and other equipment;
(3) Sampling and testing according to Table 552-9;
(4) Adjusting the mix proportions to maintain the required water/cementitious material ratio;
(5) Computing batch masses for each day's production;
(6) Checking of the plant's calibration; and
(7) Completing batch tickets. Include the following:
(a) Concrete supplier;
(b) Ticket serial number;
(c) Date and truck number;
(d) Contractor;
(e) Structure or location of placement;
(f) Mix-design and concrete class;
(g) Component quantities and concrete total volume;
(h) Moisture corrections for aggregate moisture;
(i) Total water in mix at plant;
(j) Time of batching and time at which discharge must be completed;
(k) Maximum water that may be added to the mix at the project; and
(l) If a hydration stabilizing admixture is used, the slump at the
plant
after adding
the
stabilizer.
Provide equipment necessary for the above tests and controls. Furnish copies of work sheets for (3),
(4), (5), and (7) above as they are completed.
(b) Delivery and sampling. Designate at least one certified concrete technician at the project to be
responsible for concrete delivery, discharge, and sampling including:
(1) Verifying adjustments to the mix comply with the specifications before discharge;
(2) Completing the batch ticket for each load by, recording the apparent water/cementitious
material ratio and the time;
(3) Sampling and testing according to Table 552-9; and
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Section 552
(4) If hydration stabilizing admixture is used, determining the slump before placement. Do not
use concrete with a slump loss of more than 2 inches (50 millimeters) as compared to the slump
recorded at the batch plant.
552.10 Temperature and Weather Conditions. Maintain the temperature of the concrete mixture just
before placement between 50 and 90 °F (10 and 32 °C), except for bridge decks between 50 and 80 °F
(10 and 27 °C).
(a) Cold weather. Cold weather is defined as a period when for more than 3 consecutive days the
following conditions exist:
(1) Average of the highest and the lowest temperatures occurring during the period from midnight
to midnight is less than 40 °F (5 °C); and
(2) Air temperature is not greater than 50 °F (10 °C) for more than one-half in a 24-hour period.
When cold weather is reasonably expected or has occurred within 7 days of anticipated concrete
placement; submit a detailed plan for the producing, transporting, placing, protecting, curing, and
temperature monitoring of concrete during cold weather. ACI 306, Guide to Cold Weather Concreting
may be used for guidance in developing the plan. Include procedures for accommodating abrupt
changes in weather conditions. Do not start placement until the plan is accepted. Allow at least 3 day
for review and approval of the plan.
Have material and equipment required for protection available at the project before commencing cold
weather concreting.
Remove snow, ice, and frost from the surfaces, including reinforcement and subgrade, against which
the concrete is to be placed. Heat surfaces that come into contact with fresh concrete to at least 35 °F
(2 °C) and maintain the temperature of these surfaces at 35 °F (2 °C) or above during concrete
placement.
Place heaters and direct ducts so as not to cause concrete drying or fire hazards. Vent exhaust flue
gases from combustion heating units to the outside of enclosures. Heat the concrete components in a
manner that is not detrimental to the mix. Do not heat cement or permit the cement to come into
contact with aggregates that are hotter than 100 °F (40 °C). Do not heat aggregates with a direct flame
or on sheet metal over fire. Do not heat fine aggregate by direct steam. Do not add salts to prevent
freezing.
Protect concrete for at least 72 hours according to Table 552-5. Protect concrete exposed in the final
construction for at least 7 days according to Table 552-5.
Furnish and place continuously recording surface temperature measuring devices that are accurate
within ±2 °F (±1 °C).
At the end of the protection period, allow the concrete to cool gradually over 24 hours at a rate not to
exceed the maximum values shown in Table 552-5. Remove protection when the concrete surface
temperature is within 25 °F (15 °C) of the ambient air temperature.
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Section 552
Table 552-5
Cold Weather Concrete Surface Temperatures
Minimum Section Size
< 12inches
12 - 36 inches
36 - 72 inches
> 72 inches
Dimension
(< 300 mm)
(300 - 900 mm)
(900 - 1800 mm)
(> 1800 mm)
Minimum temperature of
55 °F
50 °F
45 °F
40 °F
concrete during
(13 °C)
(10 °C)
(7 °C)
(5 °C)
protection period
Maximum allowable
50 °F
40 °F
30 °F
20 °F
temperature drop in a
(28 °C)
(22 °C)
(17 °C)
(11 °C)
24-hour period after end
of protection
(b) Hot weather. Hot weather is defined as any time during the concrete placement when the ambient
temperature at the work site is above 90 °F (35 °C).
Cool surfaces that come in contact with the mix to below 90 °F (35 °C) by covering with wet burlap or
cotton mats, fog spraying with water, covering with protective housing, or by other approved methods.
During placement, maintain concrete temperature by using any combination of the following:
(1) Shade the material storage areas or production equipment;
(2) Cool aggregate by sprinkling; and
(3) Cool aggregate and water by refrigeration or replacing a portion or all of the mix water with
flaked or crushed ice to the extent that the ice completely melts during mixing of the concrete.
(c) Evaporation. When placing concrete in bridge decks or other exposed slabs, limit expected
evaporation rate to less than 0.1 pound per square foot (0.5 kilograms per square meter) per hour as
determined by Figure 552-1.
When necessary, take one or more of the following actions:
(1) Construct windbreaks or enclosures to effectively reduce the wind velocity throughout the
area of placement;
(2) Use fog sprayers upwind of the placement operation to effectively increase the relative
humidity; and
(3) Reduce the temperature of the concrete according to Subsection 552.10(b).
(d) Rain. Protect the concrete from rain during and after placement.
552.11 Handling and Placing Concrete. Perform the work under Section 208, except for work under
Section 258. Construct reinforcing steel, structural steel, bearing devices, joint material, and miscellaneous
items according to the appropriate Sections.
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Section 552
(a) General. Design and construct falsework and forms according to Section 562. Remove mortar,
debris, and foreign material from the forms and reinforcing steel. Do not place concrete until the
forms, embedded material, and the adequacy of the foundation material have been inspected.
Thoroughly moisten the forms and subgrade immediately before concrete is placed against them. Use
an approved form release agent to produce a minimum of staining, air holes, and hydration
discoloration.
Handle, place, and consolidate concrete by methods that do not cause segregation and will result in
dense homogeneous concrete that is free of voids and rock pockets. Do not displace reinforcing steel or
other material that is to be embedded in the concrete during concrete placement. Do not retemper
concrete by adding water to the mix. Use temporary form spreader devices until concrete placement
precludes their need.
To use this chart:
1. Enter with air
temperature, move
up to relative
humidity.
2. Move right to
concrete
temperature.
3. Move down to
wind velocity.
4. Move left, read
approximate rate of
evaporation.
Figure 552-1
Evaporation Rate of Surface Moisture
Note: Example shown by dashed lines is for an air temperature of 65 °F
(18 °C), relative humidity of 45 percent, concrete temperature of 65 °F
(18 °C), and a wind velocity of 15 miles (24 kilometers) per hour. This
results in a rate of evaporation of
0.13 pounds per square foot
(0.63 kilograms per square meter) per hour.
404
Section 552
Place concrete continuously without interruption between planned construction or expansion joints.
Control the delivery rate, placing sequence, and construction methods to ensure fresh concrete is
always placed and consolidated against previously placed pre-initial set concrete. Do not allow time
between the placement of successive batches to exceed 30 minutes.
Do not damage previously placed concrete or break the bond between the concrete and reinforcing
steel. Keep workers off fresh concrete. Do not support platforms for workers and equipment directly
on reinforcing steel. Once the concrete is set, do not disturb the forms or reinforcing bars that project
from the concrete until it is of sufficient strength to resist damage.
(b) Sequence of placement.
(1) Substructures. Do not place loads on finished bents, piers, or abutments until concrete
cylinder tests from the same concrete cured under the same conditions as the substructure
element indicate that the concrete has at least 80 percent of its required 28-day compressive
strength.
(2) Vertical members. For vertical members less than 15 feet (4.5 meters) in height, allow the
concrete to set for at least 30 minutes before placing integral horizontal members. For vertical
members over 15 feet (4.5 meters) in height, allow the concrete to set for at least 12 hours. Do
not transfer loads from horizontal members until the concrete has reached the specified strength
and has been in place at least 7 days.
Do not mount friction collars or falsework brackets on vertical members until the concrete has
cured for at least 7 days or has reached specified strength.
(3) Superstructures. Place concrete in the superstructure only after the substructure forms are
stripped to allow inspection of the supporting concrete.
For concrete placed in T-beams or deck girders with depths greater than
48 inches
(1200 millimeters), allow 5 days cure time for the stem concrete before placement of the top or
deck slab.
For box girders, place the bottom slab and stems in one or separate placements. Do not place the
top slab until the stems have 5 days cure time.
(4) Arches. Place concrete for arches in alternate lateral sections to minimize shrinkage stresses.
Take into account deflections of the arch centering. Place other sections symmetrically with
respect to the center of the bridge span. Where wide barrel arches require a longitudinal joint,
place concrete on each side of such joint independently of the centering to avoid relative
settlements. Bond the sections together with suitable keys or dowels.
(5) Box culverts. Place the box culvert base slab and allow 24 hours before the remainder of the
culvert is constructed.
(6) Precast elements. Place and consolidate concrete so that shrinkage cracks are not produced
in the member.
(c) Placing methods. Use equipment of sufficient capacity that is designed and operated to prevent
mix segregation and mortar loss. Do not use equipment that causes vibrations that could damage the
freshly-placed concrete. Do not use equipment with aluminum parts that come in contact with the
concrete. Remove set or dried mortar from inside surfaces of placing equipment.
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Section 552
Place concrete as near as possible to its final position. Consolidate concrete in horizontal layers greater
than 18 inches (450 millimeters) thick. Do not exceed the vibrator capacity to consolidate and merge
the new layer with the previous layer. Do not place concrete at a rate that exceeds the design loading of
the forms.
Do not drop unconfined concrete more than 5 feet (1.5 meters). Concrete may be confined by using a
tube fitted with a hopper head or other approved device that prevents mix segregation and mortar
spattering. This does not apply to cast-in-place piling or drilled shaft when concrete placement is
completed before initial set occurs in the bottom of the piling.
Operate concrete pumps so that a continuous stream of concrete without air pockets is delivered at the
tube discharge.
(d) Consolidation. Provide sufficient hand-held internal concrete vibrators or mechanical vibrator
gangs suitable for the conditions of concrete placement. Use vibrators conforming to Table 552-6.
Provide rubber-coated vibrators when epoxy-coated reinforcement is used.
Provide a spare vibrator at the site in case of breakdown. Use external form vibrators only when the
forms have been designed for external vibration and when internal vibration is not possible.
Table 552-6
Hand Held Vibratory Requirements
Head Diameter
Frequency
Radius of Action
(vibrations/minute)
¾ - 1½ inches
3 - 6 inches
9,000 - 15,000
(20 to 40 mm)
(75 - 150 mm)
1¼ - 2½ inches
5 - 10 inches
8,500 - 12,500
(30 - 65 mm)
(130 - 250 mm)
2 - 3½ inches
7 - 14 inches
8,000 - 12,000
(50 - 90 mm)
(180 - 350 mm)
Consolidate concrete by mechanical vibration immediately after placement. Manipulate vibrators to
thoroughly work the concrete around reinforcement, embedded fixtures, corners, and angles in the
forms. Do not cause segregation. Do not consolidate concrete placed underwater. Supplement
vibration with spading, as necessary, to ensure smooth surfaces and dense concrete along form
surfaces, in corners, and at locations impossible to reach with the vibrators.
Vibrate the concrete at the point of deposit and at uniformly spaced points not farther apart than one
and one-half times the radius over which the vibration is visibly effective. Insert vibrators so that the
affected vibrated areas overlap. Do not use vibrators to move concrete. Insert vibrators vertically and
slowly withdraw from the concrete. Vibrate with sufficient duration and intensity to thoroughly
consolidate the concrete, but not to cause segregation. Do not vibrate at one point long enough to cause
localized areas of grout to form. Do not vibrate reinforcement.
(e) Underwater placement. Underwater placement of concrete is permitted only for concrete mixtures
designed for underwater placement according to Subsection 552.03. Use tremies, concrete pumps, or
other approved methods for placement.
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Section 552
(1) Tremies. Use watertight tremies, with a sufficient to ensure that aggregate-induced blockages
will not occur Use multiple tremies as required. Make tremies capable of being rapidly lowered
to retard or stop the flow of concrete.
Seal the discharge end and fill the tremie tube with concrete at the start of concrete placement.
Keep the tremie tube full of concrete to the bottom during placement. If water enters the tube,
withdraw the tremie and reseal the discharge end. Maintain continuous concrete flow until the
placement is completed.
(2) Concrete pumps. Use pumps with a device at the end of the discharge tube to seal out water
while the tube is first being filled with concrete. When concrete flow is started, keep the end of
the discharge tube full of concrete and below the surface of the deposited concrete until
placement has been completed.
Place underwater concrete continuously from start to finish in a dense mass. Place each succeeding
layer of concrete before the preceding layer has taken initial set using more than one tremie or pump if
necessary. Keep the concrete surface as horizontal as practical. Do not disturb after placement.
Maintain still water at the point of deposit.
Dewater after test specimens cured under similar conditions indicate that the concrete has sufficient
strength to resist the expected loads. Remove laitance or other unsatisfactory material from the
exposed concrete.
(f) Concrete railings and parapets. Use smooth, tight-fitting, rigid forms. Neatly miter corners. Place
concrete railings and parapets after the falsework for the supporting span is released. Remove forms
without damaging the concrete. Finish corners to be true, clean-cut, and without cracks, spalls, or other
defects.
Cast precast railing members in mortar-tight forms. Remove precast members from molds as soon as
the concrete has sufficient strength to be self-supporting. Protect edges and corners from chipping,
cracking, and other damage. Cure according to Subsection 552.15(b). The curing period may be
shortened when approved; use moist heat, Type III portland cement, or water reducing agents.
552.12 Construction Joints. Provide construction joints at locations shown in the plans. Obtain approval
for additional construction joints.
Extend reinforcing steel uninterrupted through construction joints. Embed lap splices or mechanical
splices within the concrete. Do not use dowels. At horizontal construction joints, place gauge strips inside
the forms along exposed faces to produce straight joint lines.
When the joint is between fresh and newly hardened concrete, rough float the first placement to
thoroughly consolidate the surface and leave the surface in a roughened condition. Clean the joint surface
of laitance, curing compound, and other foreign material. Use an abrasive blast or other approved method
to expose the aggregate on the joint surface. Re-tighten forms where the joint overlaps the first placement.
Immediately before placing new concrete, flush the joint surface with water and allow it to dry to a surface
dry condition.
When the joint is between existing concrete and a new placement, abrasive blast clean or use other
approved methods to remove laitance and foreign material, to expose clean aggregate, and to roughen the
joint surface. Before concrete placement, apply approved bonding products to the joint surface according
to the manufacturer’s recommendation.
407
Section 552
552.13 Expansion and Contraction Joints.
(a) Open joints. Form open joints with a wooden strip, metal plate, or other approved material.
Remove the joint forming material without chipping or breaking the corners of the concrete. Do not
extend reinforcement across an open joint.
(b) Filled joints. Cut pre-molded expansion joint filler to the shape and size of the surface being
jointed. Secure the joint filler on one surface of the joint using galvanized nails or other acceptable
means. Splice according to the manufacturer’s recommendations. After form removal, remove and
neatly cut concrete or mortar that has sealed across the joint. Fill joint gaps ⅛ inch (3 millimeters) or
wider with approved filler. Place necessary dowels, load transfer devices, and other devices as shown
in the plans or as directed.
(c) Steel joints. Fabricate plates, angles, or other structural shapes accurately to conform to the
concrete surface. Set joint opening to conform to the ambient temperature at the time of concrete
placement. Securely fasten the joints to keep them in correct position. Maintain an unobstructed joint
opening during concrete placement.
(d) Compression joint seals. Use one-piece compression joint seals for transverse joints and the
longest practical length for longitudinal joints. Clean and dry joints and remove spalls and
irregularities. Apply a lubricant adhesive as a covering film to both sides of the seal immediately
before installation. Compress the seal and place it in the joint as recommended by the manufacturer.
Make sure the seal is in full contact with the joint walls throughout its length.
Remove and discard seals that are twisted, curled, nicked or improperly formed. Remove and reinstall
joint seals that elongate more than 5 percent of their original length when compressed. Remove excess
lubricant-adhesive before it dries.
(e) Elastomeric expansion joint seal. Install the joint according to the manufacturer’s
recommendations and according to the plans.
552.14 Finishing Plastic Concrete. Strike off concrete surfaces that are not placed against forms. Float
finish the concrete surface. Remove laitance or thin grout. Carefully tool non-chamfered edges with an
edger. Leave edges of joint filler exposed.
Protect the surface from rain damage.
Provide at least two non-sagging and non-vibrating work bridges capable of supporting the workers and
equipment during placement, finishing, and curing operations. Place the work bridges at a reasonable
height above the concrete surface to not impede worker performance and not touch the finished or fresh
concrete surface.
(a) Striking off and floating. For bridge decks or top slabs of structures serving as finished
pavements, use an approved power driven finishing machine equipped with a screed that oscillates in a
transverse direction. Use hand-finishing methods for irregular areas when approved.
Strike off surfaces. Do not support rails within the limits of the concrete placement without approval.
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Section 552
Set rails or headers on non-yielding supports so the finishing equipment operates without interruption
over entire surface being finished. Extend rails beyond both ends of the scheduled concrete placement
a sufficient distance to enable finishing machine to finish the concrete being placed.
Set rails the entire length of continuous girder structures before placing deck concrete.
Adjust rails, headers, and strike-off equipment to the required profile and cross-section allowing for
anticipated settlement, camber, and deflection of falsework.
Before beginning delivery and placement of concrete, operate the finishing machine over the entire
area to be finished to check for excessive rail deflections, deck thickness, reinforcing steel cover, and
to verify proper operation of equipment. Make necessary corrections before concrete placement
begins.
After placing the concrete, operate finishing machine over the concrete as needed to obtain the
required profile and cross-section. Keep a slight roll of excess concrete in front of the cutting edge of
the screed at all times. Maintain this excess of concrete to the end of the pour or form and then remove
and waste it. Adjust rails or headers as necessary to correct for unanticipated settlement or deflection.
Remove rail supports embedded in the concrete to at least 2 inches (50 millimeters) below the finished
surface. Clean the voids of dust and debris using compressed air or other means. Apply approved
bonding material in the voids. Fill the voids with fresh concrete of the same type and property as
previously placed. Finish the surface with a float, roller or other approved device as necessary to
remove local irregularities.
Remove excess water, laitance, or foreign material brought to the surface using a squeegee or
straightedge drawn from the center of the slab towards either edge. Do not apply water to the surface
of the concrete during finishing operations.
(b) Straightedging. Check slab and sidewalk surfaces. Check the entire surface parallel to the
centerline of the bridge with a 10-foot (3-meter) metal straightedge. Overlap the straightedge at least
half the length of the previous straightedge placement.
Correct deviations in excess of ⅛ inch (3 millimeters) from the testing edge of the straightedge. For
deck surfaces that are to receive an overlay, correct deviations in excess of ¼ inch (6 millimeters).
(c) Texturing. Finish after floating or at a time when finishing operations will not displace aggregate.
Produce a skid-resistant surface texture on driving surfaces by grooving. Use one of the following or a
combination finishes for other surfaces as required.
(1) Grooved finish. Use a float having a single row of fins or an approved machine designed
specifically for sawing grooves in concrete pavements. Space fins
½ to ¾ inch (13 to
20 millimeters) on centers. Make the grooves 116 to 316 inch (2 to 5 millimeters) wide and ⅛ to
316 inch (3 to 5 millimeters) deep. Groove perpendicular to the centerline without tearing the
concrete surface or loosening surface aggregate.
If grooves are sawn, cut the grooves approximately ¼ inch (6 millimeters) wide at a spacing of
½ to 1 inch (13 to 25 millimeters).
On bridge decks, discontinue grooving 12 inches (300 millimeters) from curb face and provide a
longitudinal troweled finish on the surface of gutters.
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Section 552
(2) Sidewalk finish. Strike off the surface using a strike board and then float the surface. Use an
edging tool on edges and expansion joints. Broom the surface using a broom with stiff bristles,
broom perpendicular to the centerline from edge to edge with adjacent strokes slightly
overlapped. Produce regular corrugations not over ⅛ inch (3 millimeters) in depth without
tearing the concrete. Correct porous spots, irregularities, depressions, small pockets, and rough
spots while the concrete is plastic. Groove contraction joints at the required interval using an
approved grooving tool.
(3) Troweled and brushed finish. Use a steel trowel to produce a slick, smooth surface free of
bleed water. Brush the surface with a fine brush using parallel strokes.
(4) Exposed aggregate finish. Strike off the surface using a strike board and then float the
surface. Use an edging tool on transverse and longitudinal joints that are against forms or
existing pavement. Do not edge transverse joints in a continuous lane pour or longitudinal joints
in a continuous dual lane pour.
Broom the surface as soon as the concrete hardens sufficiently to prevent particles of gravel from
being dislodged. Use stiff brushes approved by the CO. Exercise care to prevent marring of the
surface and cracking or chipping of slab edges or joints. Apply a light spray of retardant to the
unfinished surface to facilitate this work if approved.
Broom transversely across the pavement. Pull the loosened semi-stiff mortar off the pavement.
Remove the mortar from adjacent pavements. Then broom parallel to the pavement centerline.
Continue this operation until a sufficient quantity of coarse aggregate is exposed. Other methods
of aggregate exposure, such as using a water spray attachment on a special exposed aggregate
broom, will be permitted if satisfactory results are demonstrated.
After curing according to Subsection 552.15(b) or (c), wash the surface with water and brush to
remove laitance and cement from the exposed coarse aggregate.
(d) Surface underneath bearings. Finish bearing surfaces to within ⅛ inch (5 millimeters) of plan
elevation.
When a masonry plate is to be set:
(1) Directly on the concrete or on filler material less than ⅛ inch (5 millimeters) thick; finish the
surface with a float to an elevation slightly above plan elevation. Grind the surface as necessary to
provide a full and even bearing after the concrete has set.
(2) On filler material between ¼ and ½ inch (6 to 13 millimeters) thick; finish the surface with a
steel trowel. Finish or grind the surface so that it does not vary from a straightedge in any direction
by more than ¼ inch (6 millimeters).
(3) On filler material greater than ½ inch (13 millimeters) thick or when an elastomeric bearing pad
is to be used; finish the surface to a plane surface free of ridges.
When required under a masonry plate or elastomeric bearing pad, use nonshrink grout. Proprietary
products may be used with approval.
(e) Surface underneath waterproofing membrane deck seal. Finish to a smooth surface, free of
ridges and other projections.
410
Section 552
552.15 Curing Concrete. Begin curing immediately after the free surface water has evaporated and the
finishing is complete. If the surface of the concrete begins to dry before the selected cure method can be
implemented, keep concrete surface moist using a fog spray without damaging the surface.
Keep surfaces to be rubbed moist after forms are removed. Cure immediately following the first rub.
Cure the top surfaces of bridge decks using the liquid membrane curing compound method combined with
the water method. Apply liquid membrane curing compound immediately after finishing. Apply the water
cure within 4 hours after finishing.
Cure concrete uninterrupted for at least 7 days. If pozzolans in excess of 10 percent by mass of the
hydraulic cement is used in the mix, cure uninterrupted for at least 10 days.
(a) Forms in-place method. For formed surfaces, leave the forms in-place without loosening. If forms
are removed during the curing period to facilitate rubbing, only strip forms from those areas able to be
rubbed during the same shift. During rubbing, keep the surface of the exposed concrete moist. After
the rubbing is complete, continue curing process using the water method for the remainder of the
curing period.
(b) Water method. Keep the concrete surface continuously wet by ponding, spraying, or covering
with material that is kept continuously and thoroughly wet. Covering material may consist of cotton
mats, multiple layers of burlap, or other approved material that does not discolor or otherwise damage
the concrete.
Cover the covering material with a waterproof sheet material that prevents moisture loss from the
concrete. Use the widest sheets practical. Lap adjacent sheets at least 6 inches (150 millimeters), and
tightly seal seams with pressure sensitive tape, mastic, glue, or other approved methods. Secure
material so that wind does not displace it. Immediately repair sheets that are broken or damaged.
(c) Liquid membrane curing compound method. Do not use the liquid membrane method on
surfaces to receive a rubbed finish. Use on construction joint surfaces is permitted only if the
compound is removed by sandblasting before placement of concrete against the joint.
Only use Type 2, white-pigmented liquid membrane on the top surfaces of bridge decks or on surfaces
not exposed to view in the completed work. Use Type 1-D clear curing compounds on other surfaces
and on colored concrete.
Mix membrane curing solutions containing pigments before use. Continue to agitate during
application. Use equipment capable of producing a fine spray. Apply the curing compound at a
minimum rate of 1 gallon per 150 square feet (0.25 liters per square meter) in one or two uniform
applications. If the solution is applied in 2 applications, follow the first application with the second
application within 30 minutes, and apply at right angles to the first application.
Immediately apply a new coat over the damaged areas if the membrane is damaged by rain or other
means during the curing period.
552.16 Finishing Formed Concrete Surfaces. Remove and replace or repair, as approved, rock pockets
or honeycombed concrete. Finish sound, formed concrete surfaces as follows:
411
Section 552
(a) Class 1 - Ordinary surface finish. Finish the following surfaces with a Class 1, ordinary surface
finish:
(1) Under surfaces of slab spans, box girders, filled spandrel arch spans, and the roadway deck
slab between superstructure girders;
(2) Inside vertical surface or T-girders of superstructures; and
(3) Surfaces to be buried and culvert surfaces above finished ground that are not visible from the
traveled way or a walkway.
Begin finishing as soon as the forms are removed. Remove fins and irregular projections from surfaces
that are exposed or will be waterproofed. Remove bulges and offsets with carborundum stones or
discs. Remove localized, poorly-bonded rock pockets or honeycombed concrete, and replace with
sound concrete or packed mortar in an approved manner.
Clean and point form tie cavities, holes, broken corners and edges, and other defects. Saturate the area
with water. Finish the area with mortar that is less than 1-hour old. After the mortar is set, rub it (if
required) and continue curing. Match exposed surfaces to surrounding concrete.
Carefully tool and remove free mortar and concrete from construction and expansion joints. Leave
joint filler exposed for its full length with clean, true edges.
Rub or grind bearing surfaces on piers and abutments to the specified elevation and slope.
If the final finished surface is not true and uniform, rub it according to Subsection 552.16(b).
(b) Class 2 - Rubbed finish. Finish the following surfaces with a Class 2, rubbed finish:
(1) Surfaces of bridge superstructures, except those surfaces designated to receive a Class 1 or
other finish;
(2) Surfaces of bridge piers, piles, columns and abutments, and retaining walls above finished
ground and to at least 12 inches (300 millimeters) below finished ground;
(3) Surfaces of open spandrel arch rings, spandrel columns and abutment towers;
(4) Surfaces of pedestrian undercrossings, except floors and surfaces to be covered with earth;
(5) Surfaces above finished ground of culvert headwalls and endwalls when visible from the
traveled way or walkway;
(6) Inside surfaces of culvert barrels higher than 48 inches (1200 millimeter) that are visible from
the traveled way. Finish for a distance inside the barrel at least equal to the height of the culvert;
and
(7) Surfaces of railings.
Complete a Class 1 finish according to Subsection 552.16(a). Saturate the concrete surface with water.
Rub the surface with a medium coarse carborundum stone using a small quantity of mortar on its face.
Use mortar composed of cement and fine sand mixed in the same proportions as the concrete being
finished. Continue rubbing until form marks, projections, and irregularities are removed and a uniform
surface is obtained. Leave the paste produced by this rubbing in place.
412
Section 552
After other work which could affect the surface is complete; rub with a fine carborundum stone, and
water until the entire surface has a smooth texture and uniform color. After the surface has dried; rub it
with burlap to remove loose powder. Leave the surface without unsound patches, paste, powder, and
objectionable marks.
(c) Class 3 - Tooled finish. Do not use mortar blocks or wires to set reinforcing steel near the formed
surface of areas to receive a tooled finish. Complete a Class 1 finish according to Subsection
552.16(a). Let the concrete set for at least 14 days or longer if necessary to prevent the aggregate
particles from being picked out of the surface. Use air tools (such as a bush hammer, pick, or crandall).
Chip away the surface mortar, and break the aggregate particles to expose a grouping of broken
aggregate particles in a matrix of mortar. Produce a tooled finish on a small test area for approval
before proceeding. Adjust the work procedures to produce a satisfactory finish and use those same
procedures to finish the designated area.
(d) Class 4 - Sandblasted finish. Complete a Class 1 finish according to Subsection 552.16(a). Let
the concrete cure for at least 14 days. Protect adjacent surfaces that are not to be sandblasted. Sandblast
a small test area for approval before proceeding. Use hard, sharp sand to produce an even fine-grained
surface in which the mortar is cut away leaving the aggregate exposed. Do not remove mortar beyond
one-third the diameter of the coarse aggregate.
(e) Class 5 - Wire brushed or scrubbed finish. Complete a Class 1 finish according to Subsection
552.16(a). Begin as soon as the forms are removed. Scrub the surface with stiff wire or fiber brushes
using a solution of muriatic acid. Mix the solution in the proportion of 1 part acid to 4 parts water.
Scrub until the cement film or surface is completely removed and the aggregate particles are exposed.
Leave an evenly pebbled texture having the appearance of fine granite to coarse conglomerate
depending upon the size and grading of aggregate. Wash the entire surface with water containing a
small quantity of ammonia.
(f) Class 6 - Color finish. Build a sufficient number of 24- by 48-inch (600- by 1200-millimeter)
concrete color sample panels to obtain a color acceptable to the CO. Protect the approved color sample
panel. Color designated surfaces to match the color of the approved sample.
Complete a Class 1 finish according to Subsection 552.16(a). Do not apply the color finish until
concrete placement for the structure is complete. Remove dust, foreign matter, form oil, grease, and
curing compound with a 5 percent solution of trisodium phosphate and then rinse the concrete surface
with clean water.
Use paper, cloth, or other means to protect surfaces not to be color finished. Apply the finish to a dry
concrete surface when the surface temperature is 40 °F (4 °C) or higher and the air temperature in the
shade is anticipated to be 40 °F (4 °C) or higher during the 24 hours following application.
Apply the color finish according to the manufacturer’s recommendations. Spray, brush, or roll on the
first coat of penetrating sealer and color base. Spray, brush, or roll on the finish coat after the first coat
has thoroughly dried. Apply finish to provide a uniform, permanent color, without runs and sags to the
surfaces.
Clean concrete areas not intended to be covered by the finish using an approved method.
413
Section 552
552.17 Concrete Anchorage Devices. Use chemical, grouted, or cast-in-place concrete anchorage devices
for attaching equipment or fixtures to concrete.
Furnish the following for approval:
(a) Concrete anchorage device sample;
(b) Manufacturer’s installation instructions; and
(c) Material data and certifications.
Fabricate metal parts of the anchorage devices from stainless steel or from steel protected with a corrosion
resistant metallic coating that does not react chemically with concrete. Supply anchorage devices complete
with hardware.
For chemical or grouted anchors, conduct a system approval test on one anchor on the project, not to be
incorporated in the work. Conduct a static load test according to ASTM E488. Demonstrate that the
anchorage device can withstand a sustained direct tension test load not less than the values shown in Table
552-7 for at least 48 hours with movement not to exceed 132 inch (1 millimeter). Also demonstrate that
when loaded to failure, the anchor device demonstrates a ductile failure of the anchor steel, not a failure of
the chemical, grout, or concrete.
Table 552-7
Sustained Load Test Values
Anchorage Device
Tension Test
Stud Size
Load
¾ inch
5,000 lb
(M20)
(24 kN)
⅝ inch
4,100 lb
(M16)
(18.3 kN)
½ inch
3,200 lb
(M12)
(12.7 kN)
⅜ inch
2,100 lb
(M8)
(7.1 kN)
Install concrete anchorage devices as recommended by the device manufacturer and so that the attached
equipment or fixtures bear firmly against the concrete. Torque installed nuts to the values specified in
Table 552-8 unless otherwise specified in the manufacturer’s instructions. Set bearing anchor bolts
according to the requirements of Section 564.
In the presence of the CO, proof load a random sample of at least 10 percent of the anchors to 90 percent
of the yield stress of the steel. If an anchor fails, reset the failed anchor and proof load the reset anchor and
100 percent of remaining anchors. The proof load may be applied by torqueing against a load indicator
washer, applying a direct tension load to the anchor, or another method approved by the CO. After proof
loading, release the load on the anchor and retighten the nuts to the torque specified in Table 552-8 or
according to the manufacturer’s instructions.
414
Section 552
Table 552-8
Torque for Anchorage Devices
Anchorage Device
Torque
Stud Diameter
¾ inch
125 ft•lb
(M20)
(180 N•m)
⅝ inch
90 ft•lb
(M16)
(130 N•m)
½ inch
60 ft•lb
(M12)
(80 N•m)
⅜ inch
35 ft•lb
(M8)
(30 N•m)
552.18 Loads on New Concrete Structures. Do not allow traffic on concrete bridge decks until deck
concrete has attained the design compressive strength and has been in place
14 days or longer.
Construction loads less than 4000 pounds (1800 kilograms) may be placed on the deck 7 days after the
concrete is placed and the concrete in the entire span has attained a compressive strength of at least
70 percent of the specified design strength.
For precast concrete multi-beam sections, do not allow vehicles on any span until the grout has attained a
strength of 3,000 pounds per square inch (21 megapascals) and tie rods have been tightened.
For post-tensioned concrete structures, do not allow vehicles over 4,500 pounds (2000 kilograms) on any
span until the prestressing steel for that span is tensioned, grouted, and cured, the grout has obtained a
strength of 3,000 pounds per square inch (21 megapascals), and the tie rods are tightened. Vehicles
weighing less than 4,500 pounds (2000 kilograms) may be permitted on a span provided the mass of the
vehicle was included in the falsework design.
552.19 Concrete Repair. For concrete repairs, remove existing or new defective concrete according to
Subsection 203.04(b) and (c). After removal of deteriorated or unsound concrete, shotblast exposed
structural steel, reinforcing steel, and concrete surfaces which will be in contact with repair material
until free of rust and foreign material. Clean the sound concrete surface by flushing with clean water
from a high pressure water jet or compressed air. Remove and replace deteriorated reinforcing steel.
Before placing repair concrete, thoroughly flushing with clean water under pressure or compressed air.
If compressed air is used, provide a filter in airline to ensure that the air is oil-free. If there is an interval
of more than 24 hours between cleaning of the sound concrete surfaces that have been contaminated by
substances detrimental to good bonding, clean by abrasive shot blasting and pressurized water flushing
or remove the concrete.
For vertical and overhead concrete repairs and those horizontal repairs to areas less than 5 inches
(130 millimeters) in depth; use a non-shrink grout patching compound placed according to the
manufacturer’s recommendations.
For other repairs patches greater than 5 inches (130 millimeters) in depth, apply a bonding coat of a epoxy
resin adhesive to the surfaces of the sound existing concrete immediately before placing new concrete
against it. Follow the manufacturer’s recommendations for the epoxy resin adhesive. Repair areas using
Class A(AE) concrete.
415
Section 552
552.20 Acceptance. See Table 552-9 for sampling, testing, and acceptance requirements and the quality
characteristic category.
Material for concrete will be evaluated under Subsections
106.02 and 106.03. Furnish production
certifications with each shipment cementitious material.
The concrete mixture's slump, air content, density, and temperature will be evaluated under Subsections
106.02 and 106.04.
Concrete compressive strength will be evaluated under Subsection 106.05. The lower specification limit is
the minimum required compressive strength at 28 days (fc’) specified in the contract. Remove and replace
concrete represented by cylinders having a compressive strength less than 90 percent of the minimum
28-day strength (f’c).
Construction (including batching, placing, finishing, and curing concrete) of concrete structures will be
evaluated under Subsections 106.02 and 106.04.
Falsework and forms will be evaluated under Section 562.
Measurement
552.21 Measure the Section 552 pay items listed in the bid schedule according to Subsection 109.02 and
the following as applicable:
When measuring structural concrete by the cubic yard (cubic meter), measure in the structure.
Payment
552.22 The accepted quantities will be paid at the contract price per unit of measurement for the Section
552 pay items listed in the bid schedule, except the structural concrete contract price will be adjusted
according to Subsection 106.05. Payment will be full compensation for the work prescribed in this Section.
See Subsection 109.05.
Payment for structural concrete will be made at a price determined by multiplying the contract price by the
compressive strength pay factor.
416
Section 552
Table 552-9
Sampling, Testing, and Acceptance Requirements
Material or
Type of
Characteristic
Category
Test Methods
Sampling
Point of
Split
Reporting
Remarks
Product
Acceptance
Specifications
Frequency
Sampling
Sample
Time
(Subsection)
(Subsection)
Source
Aggregate
Measured and
Quality
Subsection
1 per
Source of
Yes
Before
(703.02)
tested for
703.01 &
material
material
producing
conformance
703.02
type
(106.04 & 105)
Mix Design
Concrete
"
All
Subsection
1 per
"
If
"
composition
552.03
mix
requested
design
Production
Produced
Measured and
Gradation
AASHTO
1 per
Flowing
Yes
Before
aggregate
tested for
T 27 & T 11
day
aggregate
batching
(fine & coarse)
conformance
stream
(106.04)
(bin, belt,
discharge
conveyor belt,
or stockpile)
Fineness
AASHTO
"
"
"
modulus
T 27
Moisture test
AASHTO
"
"
"
T 255
417
Section 552
Table 552-9 (continued)
Sampling, Testing, and Acceptance Requirements
Material or
Type of
Characteristic
Category
Test Methods
Sampling
Point of
Split
Reporting
Remarks
Product
Acceptance
Specifications
Frequency
Sampling
Sample
Time
(Subsection)
(Subsection)
Production (continued)
Concrete
Measured and
Density
AASHTO
1 per
Point of
No
Upon
(552.09(b))(1)
tested for
T 121
load after
discharge
completing
conformance
at least
tests
(106.04)
0.25 yd3
(0.2 m3)
is discharged(4)
Air content
AASHTO
"
"
No
"
T 152 or
AASHTO
T 196
Slump
AASHTO
"
"
No
"
T 119
Temperature
ASTM
"
"
No
"
C1064
Concrete
Statistical
Compressive
II
AASHTO
1 set per
Discharge
Yes
28
Deliver
(552.09(b))(1)
(106.05)
strength(2)(3)
T 23 & T 22
30 yd3
stream at
days
verification
(28-day)
(25 m3),
point of
cylinders to
but not less
placing
the CO or
than 1 per
designated
day and
laboratory
not less than
for scheduled
5 sets total
testing
(1) Sample according to AASHTO R 60, except composite samples are not required.
(2) Cast at least four compressive strength test cylinders for 6- by 12-inch (150- by 300-millimeter) specimens or six compressive strength cylinders for 4- by 8-inch
(100- by 200-millimeter) and carefully transport the cylinders to the job site curing facility.
(3) A single compressive strength test result is the average result from two 6- by 12-inch (150- by 300-millimeter) or three 4- by 8-inch (100- by 200-millimeter)
cylinders cast from the same load.
(4) If three successive samples are tested and compliance to the specifications is indicated, screening tests may be reduced to an approved frequency. Resume initial
testing frequency if a test shows a failing temperature, air content, slump, or when directed.
(5) If the point of placement is different from the point of discharge, correlate the discharge tests with the placement tests to document the changes.
418
Section 553
Section 553. — PRESTRESSED CONCRETE
Description
553.01 This work consists of prestressing precast or cast-in-place concrete by furnishing, placing, and
tensioning prestressing steel. This work also includes installing precast, prestressed members, except
piling.
Material
553.02 Conform to the following Section and Subsections:
Anchorage devices
722.01
Elastomeric bearing (pads)
717.10(a)
Grout for post-tensioned structures
725.13(c)
Prestressing steel
709.02
Reinforcing steel
709.01
Structural concrete
552
Construction Requirements
553.03 Qualifications. Submit the following for approval at least 30 days before prestressed concrete
operations begin:
(a) Professional engineer. Name of the engineer who is certified by PCI for Plant Quality
Personnel, Level I or higher and is not directly employed by the precast concrete manufacturing
plant;
(b) Precast concrete manufacturing Plant and Quality Control Manager. Name and appropriate
certifications;
(c) Grouting supervisor. Name and a résumé describing experience on projects of similar
complexity and American Segmental Bridge Institute (ASBI) grouting certification; and
(d) Grouting personnel. Names and a résumé describing their experience on projects of similar
complexity.
553.04 Method Approval. Perform prestressing by either pre-tensioning or post-tensioning methods. If a
method is proposed that is not in the contract, submit detailed drawings of the method, material, and
equipment proposed for approval at least 30 days before starting prestressing. Include the following:
(a) Method and sequence of stressing;
(b) Complete specifications, details, and test results for the prestressing steel and anchoring devices;
(c) Anchoring stresses;
(d) Arrangement of the prestressing steel in the members;
419
Section 553
(e) Tendon elongation calculations for jacking procedures to be used;
(f) Number, spacing, and method of draping pre-tensioned strands;
(g) Other substantiating calculations for the prestressing method;
(h) Type of tendon ducts for post-tensioning;
(i) Pressure grouting material and equipment for post-tensioning;
(j) Samples of wire or strand; and
(k) Additions or re-arrangement of reinforcing steel and changes in concrete dimensions.
For on-site casting, submit drawings showing anticipated leveling or alterations to the site. After
completion of casting, clear the site of equipment and rubbish, and restore it to an acceptable condition.
553.05 Prestressing Steel. Use prestressing steel that is bright and free of corrosion, dirt, grease, wax,
scale, rust, oil, or other foreign material that may prevent bond between the steel and the concrete. Do not
use prestressing steel that has sustained physical damage or is pitted.
One splice per strand is permitted when single strand jacking is used. When multi-strand jacking is used,
splice all the strands or no more than 10 percent of the strands. Use strands having similar properties, from
the same source, and having the same "twist" or "lay". Locate splices outside the casting bed and between
members.
Do not weld or ground welding equipment on forms or other steel in the member after the prestressing
steel is installed.
Failure of one wire in a 7-wire prestressing strand is acceptable if 85 percent of the required tension load is
attained before failure and if the failed strand does not constitute more than 2 percent of the total area of
strands in an individual beam or girder.
Extend bars using couplers which, when assembled, have a tensile strength not less than the tensile
strength of the bars.
Protect prestressing steel against physical damage, rust, or corrosion. Do not use damaged prestressing
steel.
Package prestressing steel to protect it from physical damage and corrosion during shipping and storage.
Place a corrosion inhibitor in the package. Use a corrosion inhibitor that has no deleterious effect on the
steel, concrete, or bond strength of steel to concrete. Replace or restore damaged packaging.
Mark the shipping package with a statement that the package contains high-strength prestressing steel and
a warning to use care in handling. Identify the type, kind, and quantity of corrosion inhibitor used,
including the date when placed, safety regulations, and instructions for use. Assign a lot number and tag
for identification purposes to wire, strand, anchorage assemblies, or bars shipped to the site.
553.06 Concrete. Construct prestressed concrete according to Section 552. Construct reinforcing steel
according to Section 554.
420
Section 553
Make at least one set release strength test cylinders according to AASHTO T 23 in addition to those
required to determine the 28-day compressive strength. Cure the release strength test cylinders with the
concrete member they represent.
Rough cast the top surface of members against which concrete will be cast. Finish surfaces to be covered
with a waterproofing membrane deck seal to a smooth surface free of ridges and other projections.
Cure the girder in a saturated atmosphere of at least 90 percent relative humidity. Cure time may be
shortened by heating the outside of impervious forms with radiant heat, convection heat, conducted steam,
or hot air.
Apply radiant heat by pipes circulating steam, hot oil, hot water, or electric heating elements. Inspect
casting beds to ensure uniform heat application. Use a suitable enclosure to contain the heat. Minimize
moisture loss by covering exposed concrete surfaces with plastic sheeting or liquid membrane curing
compound according to Subsection 552.15. Sandblast curing compound from surfaces to which concrete
will be bonded.
Envelop the entire surface with saturated steam. Completely enclose the casting bed with a suitable type of
housing, tightly constructed to prevent the escape of steam and exclude outside air. Use steam at
100 percent relative humidity. Do not apply the steam directly to the concrete.
With hot air, the CO will approve the method to envelop and maintain the girder in a saturated atmosphere.
Do not allow dry heat to touch the girder surface.
With heat curing methods:
(a) Keep unformed girder surfaces in a saturated atmosphere throughout the curing time.
(b) Embed a thermocouple, linked with a thermometer accurate to ±5 °F (±3 °C), 6 to 8 inches (150 to
200 millimeters) from the top or bottom of the girder on its centerline and near its midpoint.
(c) Monitor with a recording sensor, accurate to ±5 °F (±3 °C), arranged and calibrated to continuously
record, date, and identify concrete temperature throughout the heating cycle.
(d) Make the temperature record available to the CO.
(e) Heat concrete to no more than 100 °F (38 °C) during the first 2 hours after placing concrete, and
increase the temperature no more than 40 °F (22 °C) per hour to a maximum of 160 °F (71 °C).
(f) Cool concrete, after curing is complete, no more than 40 °F (22 °C) per hour until a temperature
20 °F (11 °C) above the temperature of the air to which the concrete will be exposed has been reached.
(g) Keep the temperature of the concrete above 60 °F until the girder reaches release strength.
Cure precast, prestressed members to the release compressive strength. This is when the average strength
of two representative test cylinders is greater than the minimum required strength and the individual
strength of any one cylinder is no more than 5 percent below the required strength.
553.07 Tensioning. Use hydraulic jacks to tension prestressing steel. Use a pressure gauge or load cell for
measuring jacking force.
421
Section 553
Calibrate measuring devices at least once every 6 months or if they appear to be giving erratic results.
Calibrate the jack and gauge as a unit with the cylinder extension in the approximate position that it will be
at final jacking force. Keep a certified calibration chart with each gauge.
If a pressure gauge is used, do not gauge loads less than ¼ nor more than ¾ of the total graduated capacity
of the gauge, unless calibration data clearly establishes consistent accuracy over a wider range. Use a
pressure gauge with an accurate reading dial at least 6 inches (150 millimeters) in diameter.
Measure the force induced in the prestressing steel using calibrated jacking gauges, load cells, or a
calibrated dynamometer. Take elongation measurements of the prestressing steel. Determine the required
elongation from average load-elongation curves for the prestressing tendons used.
For pre-tensioned members, if there is a discrepancy between the gauge pressure and elongation of more
than 5 percent in tendons over 50 feet (15 meters) in length or 7 percent in tendons of 50 feet (15 meters)
or less in length determine the source of error before proceeding. Do not allow discrepancies in
post-tensioned members to exceed 7 percent.
If the jacking system is equipped with an automatic release valve that closes when the required
prestressing force is reached, strand elongation measurements are only required for the first and last tendon
tensioned and for at least 10 percent of the remaining tendons.
If a load cell is used, do not use the lower 10 percent of the manufacturer’s rated capacity of the load cell
to determine the jacking force.
Do not exceed a temporary tensile stress of 80 percent of the specified minimum ultimate tensile strength
of the prestressing steel. Anchor prestressing steel at an initial stress that will result in the retention of a
working stress after all losses of not less than those required.
For pre-tensioned members, do not allow the initial release stress after seating, and before other losses, to
exceed 70 percent of the specified minimum ultimate tensile strength of the prestressing steel for
stress-relieved strands and 75 percent for low-relaxation strands. For post-tensioned members, do not
allow the initial release stress after seating to exceed 70 percent of the specified minimum ultimate tensile
strength of the prestressing steel.
553.08 Pre-tensioned Members. Cast pre-tensioned members to the tolerances shown in Table 553-1.
(a) Prestressing steel. Protect prestressing steel placed in the stressing bed from contamination and
corrosion if the stressing bed is to be exposed to weather for more than 36 hours before encasement in
concrete.
Free strands of kinks or twists. Accurately hold prestressing steel in position and tension according to
Subsection 553.06. Do not allow strands to unwind more than one turn. Keep a record of the jacking
force and elongation measurements after the strands are tensioned to 20 percent of final jacking force.
Tension prestressing steel to the required stress. Include in elongation computations strand anchorage
slippage, splice slippage, in place horizontal movement of the structural member during prestressing
operations, and prestressing steel temperature changes between the time of tensioning and the time
when the concrete takes its initial set. Computations must be prepared by a professional engineer.
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Section 553
Maintain the prestress bed forms, strands, and reinforcement bar temperature within 25 °F (14 °C) of
the temperature of the concrete to be placed in the forms. Support strands with rollers at points of
direction change when strands are tensioned in a draped position. Use free-running rollers with
minimal friction. Initially, when strands are tensioned and then pulled into the draped position, tension
to no more than the required tension minus the increased tension due to forcing the strand to a draped
profile. If the load in a draped strand at the dead end, as determined by elongation measurements, is
less than 95 percent of the jack load, tension the strand from both ends of the bed. Make the load, as
computed from the sum of elongations produced by jacking at both ends, agree within 5 percent of the
jack load.
Within 3 hours before placing concrete, check the tension on the prestressing strands. The method and
equipment for checking the loss of prestress will be approved by the CO. If strands are tensioned
individually, check each strand for loss of prestress. Retension to the original computed jacking stress
for strands that show a loss of prestress in excess of 3 percent. If strands are tensioned in a group,
check the entire group for total loss of prestress. Release and retension the entire group if the total
prestress shows a loss in excess of 3 percent or if individual strands appears significantly different
from the rest of the strands in the group.
(b) Releasing steel. Release the prestress load to the concrete after the concrete has attained its
required release compressive strength. Do not expose the concrete to temperatures below freezing for
at least 7 days after casting. Cut or release strands such that lateral eccentricity of the prestress force is
minimized. Cut off prestressing steel flush with the end of the member, except as noted in the plans.
(c) Debonding strands. Use solid or split plastic sheathing with a minimum thickness of 1/32 inches
(0.8 millimeters) to debond strands. Before placing concrete, use tape to thoroughly seal split and solid
sheathing including ends to prevent the migration of concrete mortar along the strand.
553.09 Storing, Transporting, and Erecting. Do not ship prestressed concrete members until concrete
cylinder tests, manufactured of the same concrete and cured under the same conditions as the members;
indicate that the concrete in each member has attained the minimum required design strength and is at least
7 days old, except decked Bulb-T sections must be at least 10 days old.
Before transporting prestressed concrete members, provide written certification from a professional
engineer conforming to the qualifications of Subsection 553.03, that the members were fabricated and
visually inspected according to the contract and meet minimum quality requirements.
Store, transport, and erect precast, prestressed girders, slab units, and box units in the upright position with
the points of support and directions of the reactions, with respect to the member, approximately the same
as when the member is in its final position. Prevent cracking or damage during hoisting, handling, and
storing of the precast units. Replace units damaged by improper handling or storing.
553.10 Post-Tensioned Members. Construct post-tensioned members to the tolerances shown in Table
553-1. Construct supporting falsework so that the superstructure is free to lift off the falsework and shorten
during post-tensioning. Detail formwork left inside box girders to support the roadway slab to offer
minimum resistance to girder shortening due to shrinkage and post-tensioning.
(a) Ducts. Use mortar-tight ducts that are sufficiently-rigid to maintain their shape and alignment
during concrete placement and grout installation. Use ducts conforming to the following minimum
wall thicknesses:
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Section 553
(1) Metal duct, 2⅝ inch (65 millimeter) diameter
26 gage (0.55 millimeter)
(2) Metal duct, > 2⅝ inches (> 65 millimeter) diameter
24 gage (0.70 millimeter)
(3) High density polyethylene (HPDE)
14 gage (2.0 millimeter)
(4) High density polypropylene (HDPP)
14 gage (2.0 millimeter)
(5) Metal duct with bar tendons preassembled
31 gage (0.25millimeter)
with duct
For tendons composed of single prestressing bars, provide ducts with a minimum internal duct
diameter of at least ¼ inch (6 millimeters) larger than the outside diameter of the prestressing bar. For
multiple wire, bar, or strand tendons, provide a duct nominal internal cross-sectional area of at least
two and one-quarter times the net area of the prestressing steel. When tendons are to be placed by the
pull through method, provide a duct nominal internal cross-sectional area of at least two and one-half
times the net area of the prestressing steel.
Make positive joints between duct sections. Do not make angles at the joints. Use waterproof tape at
the joints. Bend ducts without crimping or flattening. Use ferrous metal or polyethylene couplings to
connect ducts to anchoring devices.
Protect ducts against crushing, excessive bending, dirt contamination, and corrosive elements during
transport, handling, and storing.
In case of duct damage, seal duct with tape, or splice a duct coupler over the damaged section to form
a seal that prevents cement paste from entering the duct during the placement of concrete and to
prevent leakage during grouting operations.
Provide ducts and anchorage assemblies with inlets for the injection of grout into the duct after
prestressing according to the PTI, Guide Specification for Grouting of Post-Tensioned Structures.
Provide ducts with outlets to allow the escape of air, water, grout, and bleed water according to the
PTI, Guide Specification for Grouting of Post-Tensioned Structures.
Provide inlets and outlets with an inner diameter of at least ¾ inch (19 millimeters) for strand tendons
and of at least ½ inch (13 millimeters) for single bar tendons. Extend the length of outlets a sufficient
distance out of the concrete member to allow for the proper closing of the outlets.
Place inlets and outlets, at a minimum, in the following locations:
• Anchorage area of the tendon;
• High points of the duct, when the vertical distance between the highest and lowest point is
more than 24 inches (600 millimeters);
• Inlet at or near the lowest point of the tendon;
• Outlet at low points of the duct;
• Major changes in the cross-section of the duct, such as couplers and anchorages; and
• Outlet at a distance less than 36 inches (900 millimeter) downstream from high point outlets.
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