510PRESTRESSED CONCRETE

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5-141SECTIO N 510 – PRESTRESSE D CONCRETE

510.0 1 DESCRIPTION . This work shall consist of manufacturing, transporting, and erecting precast prestressed concrete members. 510.0 2 MATERIALS . Materials shall meet the requirements of the following subsections: Portland Cement ................................ ................................ ................................ ......... 701.02 High Early -Strength Portland Cement ................................ ................................ .......701.0 3 Portland -Pozzolan Cement ................................ ................................ ......................... 701.0 4 Portland -Limestone Cement ................................ ................................ ...................... 701.0 5 Portland Blast -Furnace Slag Cement ................................ ................................ ......... 701.0 6 Ternary Blended Cement ................................ ................................ ........................... 701.0 7 Fine Aggregate for Concrete ................................ ................................ ...................... 704.01 Coarse Aggregate for Concrete ................................ ................................ .................. 704.02 Lightweight Fine Aggregate for Concrete ................................ ................................ .704.19 Mortar, Type IV ................................ ................................ ................................ ......... 707.0 1(e) Preformed Joint Filler, Cork, and Asphalt -Treated Felt ................................ ............ 707.0 6 Polyvinyl Chloride (PVC) Waterstop ................................ ................................ ........ 707.08 Bar Reinforcement ................................ ................................ ................................ .....713.01 Prestressing Strand and Post -Tensioning Strand ................................ ....................... 713.0 4 Structural Steel ................................ ................................ ................................ ........... 714.02 High -Strength Low -Alloy Structural Steel ................................ ................................ 714.03 Carbon Steel Bolts, Nuts, and Washers ................................ ................................ .....714.04 High -Strength Structural Bolts and Assemblies, 120 ksi ................................ ........... 714.05 Concrete Curing Materials ................................ ................................ ......................... 725.01 Air-Entraining Admixtures ................................ ................................ ........................ 725.02(b) Retarding Admixtures ................................ ................................ ................................ 725.02(c) Water -Reducing Admixtures ................................ ................................ ..................... 725.02(e) Water -Reducing and Retarding Admixtures ................................ .............................. 725.02(f) Water -Reducing, High Range Admixtures ................................ ................................ 725.02(g) Water -Reducing, High Range, and Retarding Admixtures ................................ .......725.02(h) Accelerating Admix tures ................................ ................................ ........................... 725.02(i) Water -Reducing and Accelerating Admixtures ................................ ......................... 725.02(j) Specific Performance Admixtures ................................ ................................ ............. 725.02(k) Mineral Admixtures ................................ ................................ ................................ ...725.03 Polystyrene Insulation Board ................................ ................................ ..................... 735.01 Blanket Insulation Material ................................ ................................ ........................ 735.02 Pipe Insulation ................................ ................................ ................................ ........... 740.0 6 Water ................................ ................................ ................................ .......................... 745.01 Concrete Repair Material , Type I ................................ ................................ .............. 780.0 1(a) Bearing pads for structures shall meet the requirements of Section 731 . 510 5-142 510.0 3 GENERA L FABRICATIO N REQUIREMENTS .

requirements of PCI MNL -116 and PCI MNL -135, except as modified in this section .

PCI under its Plant Certification Program for prestressed concrete. The plant shall be certified at a minimum to the level of product being produced. If there is an archi tectural finish for the product, the plant shall be certified at a minimum to the level of product being produced plus the architectural certification at that level. Prestressed concrete shall be manufactured in a plant that maintains a quality control laboratory that meets the requirements of the Agency’s Qualified Laboratory Program . As a minimum, the laborat ory shall be equipped with a compression testing machine, curing room or chamber, apparatuses for measuring slump/flow and air entrainment, and a complete set of Aggregate sieves. The compression testing machine shall be calibrated yearly by an independent laborat ory using equipment that is certified by the National Institute of Standards and Technology. The testing machine shall be power -operated and capable of applying the load continuously rather than intermittently, and without shock.

Agency as to its ability and commitment to produce concrete to the requirements of this section . A satisfactory program of quality control shall include gradation and moisture determinations of the aggregates, as well as slump, air content, and strength determinations of the concrete. These tests shall be performed at regular and suitable intervals as specified in the Materials Sampling Manual and actively used to main tain the quality of the concrete within the specified requirements. The fabricator shall have a plant specific quality control plan approved by the Agency prior to the beginning of any fabrication activities. 510.0 4 SUBMITTALS . As soon as practical after award of the Contract, all required information shall be prepared and submitted. Fabrication drawings, also referred to in the precast industry as production drawings or shop drawings, for the prestressed concrete shall be sub mitted in accordance with the requirements of Subsection 105.06 , with an additional copy sent to the Structural Concrete Engineer. Fabrication drawings shall include such detail as needed to fully describe the intended as -built condition of the prestressed elements including any connections between prestressed elements or existing structures and materials.

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5-143In addition to the requirements in Subsection 105.06 , the following shall be included:

following items:

minimum, to verify that they meet the requirements of AASHTO T 84 and AASHTO T 85 for absorption and specific gravity and AASHTO T 19 for unit weight.

contributed to hy dration by all admixtures, when the cumulative total exceeds 1 gallon per cubic yard. All mix qualification test results shall be generated with concrete from batches that are produced at this maximum W/CM ratio.

The concrete shall be classified and tested as self-consolidating concrete (SCC) if the minimum spread is at least 18 inches. When the concrete is tested as a n SCC mix, the difference between the J -ring test (ASTM C1621 ) and the spread test (ASTM C1611 ), shall be 2 inches or less for the minimum and maximum spread. Concrete that fails to meet the 18 inches minimum spread threshold will be classified and tested as conventional concrete. The visual stability index (VSI) determination will be included for the minimum and maximum values and shall not be greater than 1. The concrete shall not demonstrate segregation at the minimum or maximum slump/spread.

510 5-144 d. Temperature results obtained in accordance with the requirements of ASTM C1064 .

of AASHTO T 22 for early breaks and design strength, and 28 -day standard cure results obtained in accordance with the requirements of AASHTO R 100 . The type of cure shall be l isted for each age of break.

requirements of AASHTO T 358 . Results shall be categorized as Low, Very Low, or Negligible in accordance with AASHTO T 358, Table 1. The surface resistivity may be accepted prior to 56 days if the results meet these requirements. The 56 day test results shall be completed and submitted regardless of the results of earlier tests. Testing shall be performed by an independent AASHTO re:source qualified laborat ory. Test results that are suspected to have been adversely affected due to the presence of polymeric admixtures in the proposed mix may be retested with the polymeric admixture omitted.

separately based on the requirements of AASHTO T 303 . If one or more of the aggregates exceeds 0.10% expansion, then the aggregate shall be tested again according to the requirements of ASTM C1567 . The Contractor may elect to go directly to ASTM C1567 testing if they suspect that the aggregate may exceed the 0.10% expansion if tested by AASHTO T 303. Testing shall be performed by an independent AASHTO re:source qualified laborat ory accredited in the specific test method.

AASHTO T 160 . Testing shall be performed by an independent AASHTO re:source qualified laborat ory accredited in conducting testing that mee ts the requirements of AASHTO T 160 . The maximum free shrinkage test result shall not exceed 0.06%. The cross -section of the prism shall be 4 inches × 4 inches. The requirements of AASHTO T 160 , Section 11.1.2 shall be followed for storage and measurements.

510 5-145 (7) Mix design approvals will be valid for a 12 -month period. The approved mix design will be allowed re -approval if the following conditions are satisfied:

have changed from the initial approved mix design.

volumes adjusted accordingly. The properties to be tested include , but are not limited to, specific gravity, unit weight, and absorption.

Aggregate property values will be valid for 14 months from the date tested.

completed and accepted for the initial mix design approval, as well as any

applicable updated test information.

New mix designs and mix designs that were initially approved more than 36 months ago

shall have new testing completed to be submitted for approval.

The proposed concrete mix design, including performance history and all requests for

variance from the material requirements of these specifications, shall be submitted for

approval. The Structural Concrete Engineer may require a minimum of 8 weeks for testing,

review, and approval of new mix designs.

be submitted. Fabricators shall calculate the camber estimate at the time of release and at the

estimated time of delivery. The camber control plan shall be as detailed in Subsection 510.08(i).

jack and gauge combinations shall be submitted.

pressure, elongations, and movement of anchorage abutments. A professional engineer shall

review and stamp the calculations.

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requirements of Subsection 510.09.

prestress forces.

concrete strength to allow lifting, based on calculations stamped by a professional engineer.

Lifting attachments are not required to be permanently installed in the work and may be removed

or left in place at the Contractor’s convenience, provided that the minimum clear cover

requirements are met.

All design details shall be in accordance with the VTrans Structures Design Manual and the AASHTO

LRFD Bridge Design Specifications. A professional engineer shall stamp any design calculations included

in the submittal materials.

510.05CONCRETE

provisions of Section 501 identified in Table 510.05A.

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TABLE 510.05A – BATCH PLANT OPERATION SUBSECTIONS AND TOPICS

Subsection Topic

Subsection 501.04(a) General Requirements

Subsection 501.04(d) Testing Laboratory

Subsection 501.04(e) Bins and Scales

Subsection 501.04(f) Production Tolerances for Batching

Subsection 501.04(g) Storage and Proportioning of Materials

Subsection 501.05 Mixing and Delivery

Paragraphs 1 and 3 only.

For plants not located in Vermont, the Agency has the option

of waiving the requirements of Subsection 501.05(a)(6) in

their entirety and Subsection 501.05(c), paragraph 1 only.

curing, and testing requirements.

Specimens shall be tested either at the Agency’s Materials Testing and Certification Section

Central Laboratory, or at the fabricator’s plant laboratory. An Agency representative shall witness

all tests.

Concrete for prestressed members shall conform to the following:

the design compressive strength shown on the Plans. When a 28-day test result is below

the specified design strength, all concrete represented by that test shall be unacceptable for

the requirements of this section. The Engineer reserves the right to reject all members that

were manufactured from this concrete.

water contributed to hydration by all admixtures when the cumulative total exceeds 1

gallon per cubic yard. If total cementitious material content exceeds 900 pounds per cubic

yard, then water batched shall not exceed 300 pounds per cubic yard. The maximum W/CM

ratio in production shall not exceed the maximum W/CM ratio specified in Subsection

510.04(a)(6)a

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152.

as tested in accordance with the requirements of AASHTO T 309.

the minimum and maximum slump or spread ranges submitted in the mix design, the load

may be rejected. The VSI shall be less than or equal to 1.

be cured along with the piece they represent through the complete curing period. These

cylinders shall be kept with the piece they represent until collected by the Agency as

specified by the requirements of AASHTO T 277 and AASHTO T 358.

design shall be used in the prestressed units required for any one structure, unless otherwise

authorized by the Structural Concrete Engineer. Any admixture containing calcium chloride shall

not be used.

510.06INSPECTION. Materials furnished and the work performed under the requirements of Section

shall be inspected by the Agency. The inspector shall have the authority to reject any material or work

that does not meet the requirements of these specifications. Any work performed that has not been

inspected may be rejected, unless waived in writing by the Engineer.

The inspector shall be provided with a minimum office space of 100 square feet with a least dimension of

6 feet. A desk surface with a minimum of two drawers, as well as dedicated private telephone and internet

services, shall be provided to the laboratory. The phone and internet service shall be provided in

accordance with Subsection 631.02(a)(4), except that selection of the service by the Engineer is not

required.

Any variances shall be approved by the Structural Concrete Engineer. This office space shall be located

on the premises as close to the production area as practicable.

The Engineer reserves the right to reject inadequate office facilities and require suitable alternatives.

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510.07PRESTRESSING. Prestressing shall be accomplished by the pre-tensioning method

The fabricator shall provide all equipment necessary for the prestressing operations. Prestressing shall be

done with approved jacking equipment. Hydraulic jacks shall be equipped with pressure gauges or other

indicating devices. The combination of jack and pressure gauge, or other tensioning system, shall be

accompanied by a certified calibration chart showing the relationship between the gauge reading and the

force in the ram for both ascending and descending movements of the ram. The calibration date of each

combination jack and gauge or indicating device shall be within the 12-month period immediately prior

to the start of work.

If other types of jacks are used, calibrated proving rings or other devices shall be furnished so that the

jacking force may be accurately determined.

Suitable precautions shall be taken by the fabricator to prevent accidents due to breaking of the

prestressing steel or slippage of the grips during prestressing operations.

The tensioning operation shall proceed until the calculated gauge reading has been reached. The

elongation of each strand shall then be measured. If the measured elongation differs from the theoretical

by more than 5%, the tensioning operation shall be stopped, and the cause of the discrepancy determined

prior to continuing.

Immediately after tensioning, the final position of each strand shall be marked to check any strand slippage

prior to placing concrete. If slippage is suspected or if the time between tensioning and placing concrete

exceeds 48 hours, then 10% of the total number of strands including the strands that are suspected to have

slipped shall be re-tensioned and the elongation measured. The specific strands to be re-pulled will be

selected by the Agency inspector, but no fewer than two strands shall be re-pulled.

If additional elongation is gained, the amount gained shall be subtracted from the theoretical elongation.

If the result of the theoretical elongation minus the gain in elongation is less than the minimum allowable

elongation per the requirements of PCI MNL-116 for any of the strands tested, the final force shall be

applied to all strands.

For abutment anchorage set-ups where the strands are anchored to abutments that are independent from

the form, thermal adjustments shall be made if the ambient temperature at the time of tensioning differs

by more than 25°F from the concrete temperature prior to placement and if the net force differential is

greater than 2.5%.

Consideration shall be given to partial bed length usage and adjustments made when the net effect on the

length of the bed used exceeds the allowable. The thermal coefficient of steel shall be taken as 6.5 ×

-6 /°F.

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510.08FABRICATION

of 14 calendar days prior to beginning concrete placement, unless the Engineer deems, in writing,

that a pre-production meeting is unnecessary. The meeting shall be held a minimum of 5 calendar

days prior to beginning concrete placement unless otherwise approved by the Structural Concrete

Engineer.

At a minimum, the pre-production meeting shall be attended by the crew supervisor, plant

manager, inspector or inspector’s supervisor, a representative from the Agency’s Materials Testing

and Certification Section Structural Concrete Unit, and the Project Manager or designer.

Additionally, the fabricator shall have available at the pre-production meeting the approved

fabrication drawings and a complete anticipated production schedule for all components included

in the fabrication drawings.

body of the member. Any defects or damage due to formwork, stripping, or handling may be cause

for rejection.

Forms for interior voids or holes in the members shall be constructed of a material that will

adequately resist breakage or deformation during concrete placement and that will not materially

increase the weight of the members. Interior void forms shall be accurately positioned as shown

on the Plans and secured to prevent displacement during concrete placement. All voids shall be

adequately vented to prevent damage to the members during curing. Each void shall contain a

suitably located drain hole.

Holes or cutouts for anchoring devices, diaphragm connections, openings for connection rods,

recesses for grout holes for railing bolts, and any other related details shown on the Plans shall be

provided for in the members. Where diaphragm dowels do not pass through the member, the

dowels may be attached by use of an approved anchorage embedded in the concrete member.

an approved conduit. Unless otherwise shown on the Plans, the ratio of cross-sectional area of the

tendon to be encased to the interior cross-sectional area of the conduit shall not exceed 0.4, except

when a steel bar is used as a tendon. The inside diameter of the conduit shall be at least 3/8 inch

greater than the diameter of the bar. Conduit that has been crushed or has opened seams shall not

be used.

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The conduit shall be rigidly constructed, completely sealed, accurately placed, and securely

fastened to maintain the desired profile during concreting. No conduit shall be located more than

1/4 inch from the position shown on the Plans. Bundling of conduits will not be permitted.

the center of gravity of the steel as shown on the approved shop drawings. Prestress strands shall

be protected against corrosion and be free of nicks, kinks, dirt, rust, oil, grease, and other

deleterious substances.

reinforcement shall be furnished and installed in conformance with the requirements of Section

507. The chairs or spacers used to support or locate the reinforcement that bears on the faces of

the forms shall be made of, or be coated with, a non-corrosive material so that no discoloration

will show on the faces of the prestressed concrete units.

requirements of Subsection 510.07, and in the presence of an Agency representative. The jacking

force exerted and the elongation produced shall be recorded. Several units may be cast and stressed

at one time in a continuous line. Sufficient space shall be maintained between the ends of the units

to permit access for cutting strands after the concrete has attained the required strength.

reviewed and approved the placement of the reinforcement, conduits, anchorages, and prestressing

strands.

The concrete shall be vibrated internally, externally, or a combination thereof to the required

consolidation. The vibrating shall be done with care and in such a manner that the concrete is

uniformly consolidated, any displacement of or damage to reinforcement, conduit, voids, and

prestressing strand is avoided, and acceptable finish surfaces are produced.

When a vibrator is used with rebar with special coatings or made of non-metallic material or

material that could be susceptible to damage, the vibrator head shall be non-metallic or rubber-

coated.

SCC concrete should not be vibrated. If there is a need to vibrate SCC concrete, it shall only be

vibrated for the minimum time necessary so as to avoid segregation.

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strength (f′c) has been attained, or as stated on the approved fabrication drawings. The compressive

strength shall be determined by cylinders tested in accordance with the Materials Sampling

Manual. The prestressing strands shall be released in the de-tensioning pattern detailed on the shop

drawings.

If de-tensioning is accomplished by single strand release, each strand shall be cut by gradually

heating the strand at both ends of the member simultaneously. A minimum length of 5 inches of

strand shall be heated to prevent any shock or snap when the strand is finally severed. Each strand

shall be cut at all spaces between members cast continuously, before starting de-tensioning on the

following strand in sequence.

Strands shall be cut flush and epoxy-painted unless otherwise specified on the Plans. If the strands

are required to be recessed, a block-out shall be built into the bulkhead that will allow the strands

to be cut without damaging the concrete. The recess shall be thoroughly cleaned and patched with

Type IV mortar. The mortar shall be wet cured for three days or as specified by the manufacturer.

and PCI MNL-135 unless otherwise noted in the Contract or approved by the Engineer.

The camber and differential camber between beams measured at pre-shipping inspection shall be

within PCI tolerances and shall be measured with dunnage placed under bearing areas of the beam

and at no less than 72 hours after the removal of any means of camber correction. Tolerances shall

be compared to the calculated camber estimates at the time of the pre-shipping inspection.

The camber control plan shall detail how the fabricator will achieve the calculated camber estimate

submitted in the fabrication drawings as required in Subsection 510.04(b). The fabricator shall

achieve a beam camber at time of delivery that is within PCI tolerances of the calculated camber

estimate. In addition, it is the responsibility of the Contractor to confirm at the time of fabrication

drawing review that the calculated camber estimate is compatible with the grades and elevations

of the rest of the structure.

tolerances as specified in Table 510.08A.

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TABLE 510.08A – PRESTRESS DECK PANEL TOLERANCES

Element Tolerance

Vertical position of strand group

(measured from bottom of panel) + 0 inches, - 1/8 inch

Dunnage ± 6 inches

Warping (distance from nearest

adjacent corner) 1/16 inch per foot

Finish of strands (minimum

extension beyond ends of panel) 4 inches

manufacturing site.

Minor defects are defined as the intermittent presence of holes, honey-combing, chips, or spalls,

which measure 6 inches or less in the longest dimension, and that do not penetrate deeper than 1

inch into the concrete. Minor defects may be repaired using an approved standard repair procedure

as detailed in Subsection 510.08(k)(3).

Surface voids or bug holes that are less than 5/8 inch in diameter and less than 1/4 inch deep need

not be repaired. Minor defects that recur with any identifiable regularity or pattern may be required

to be addressed through a non-conformance report (NCR), at the discretion of the Structural

Concrete Engineer.

Any defect that has the potential to affect structural capacity or integrity shall be categorized as a

major defect. It is at the sole discretion of the Structural Concrete Engineer to determine into which

category any defect is categorized.

Structural Concrete Engineer. Cracks equal to or greater than 0.01 inch in width may be

cause for rejection based on their width, length, location, and frequency. At the Structural

Concrete Engineer’s discretion, cracked members shall be repaired or replaced at the

Contractor’s expense. De-tensioning procedures causing web-splitting or other member

cracking shall be revised before de-tensioning the next bed. Cracks with a width of 0.05

inch and greater found in any member will be cause for rejection.

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the Agency’s Approved Products List. Any unsound concrete shall be carefully chipped

out and the perimeter saw-cut to a minimum depth of 1/4 inch or deeper if recommended

by the repair material manufacturer. The prepared surface profile shall be as specified by

the repair material manufacturer. If not specified, the prepared surface profile shall

conform to, at a minimum, the International Concrete Repair Institute’s CSP 6 (Medium

Scarification) surface profile. The repair material shall be cured as specified by the

manufacturer.

comprehensive documented process for repairing minor defects at the fabricator’s facility.

At a minimum, the SRP shall detail the scope of defects for which that procedure is

intended to be used, a detailed narrative including every step of the repair procedure, and

the product documentation for the specific repair materials that will be used.

The SRP shall include example pictures of defects for which the procedure could be used,

detailed example pictures covering every step of the repair procedure, and example pictures

of a successfully completed repair job.

Approval to use an SRP for any given defect is at the sole discretion of the Structural

Concrete Engineer, and all SRPs shall be approved by them prior to their use. SRPs shall

be submitted to the Structural Concrete Engineer at least 14 calendar days in advance of

the repair work. The Agency’s consent to use an SRP for the repair of a defect does not

constitute acceptance of that repair.

minor above, shall be documented with a non-conformance report (NCR). NCRs shall be

submitted within 2 working days of the discovery of the defect. At a minimum, the NCR

shall detail what the defect is, including detailed pictures of the piece and defect, and what

caused it.

The NCR shall further document the proposed repair, the procedure for carrying out the

proposed repair, and a plan of action to prevent additional similar defects from occurring.

Any approved repairs shall be documented and photographed during the repair work and

after completion of the repair.

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rejected.

crosses more than one strand.

total number of strands in the panel.

impact on the structural integrity of the deck panel.

covered with an asphalt wearing surface shall be given a finish as specified on the approved shop

drawings, or if not specified, in accordance with the requirements of Subsection 501.14.

ambient air temperature is expected to be below freezing at any point in time or below 40°F for an

8-hour continuous period. The requirements of Subsection 501.07(b) shall apply in addition to the

requirements of Subsection 510.09.

marked on each individual piece of prestressed concrete. The mark shall be in a location that will

not be visible in the finished product.

510.09CURING

Structural Concrete Engineer’s approval. The fabricator shall submit complete details of the

proposed methods for approval with the fabrication drawings.

The curing period for prestressed concrete is defined as wet curing for a minimum of 72 hours, to

begin immediately following the completion of placing and finishing of the concrete. The

following requirements shall apply:

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where modified herein, prestressed concrete structure components shall be cured by water

curing, by wetted burlap covered with white polyethylene sheeting, or by burlap-white

polyethylene sheeting (burlene) as specified in Subsection 501.15.

within the enclosure shall exceed 90% throughout the duration of the curing period. A

curing enclosure is considered any means of moisture-retention that allows air to contact

the surface of the piece.

represent, or by specimens match-cured in an approved match-curing system.

no less than 72 hours in duration.

operations. De-tensioning shall be accomplished while the product is still warm. Wet

curing shall be resumed upon removal of the product from the forms.

the concrete elements, and not the ambient temperatures of the curing area unless

specifically stated as such.

the first 12 hours of the curing period, and shall be maintained at or above 68°F for the

remainder of the entire curing period.

thermocouples placed as near as practicable to the center of mass of the finished piece. In

addition, the temperature within the curing enclosure shall be monitored using strategically

placed temperature sensors so that the reported temperatures accurately represent the

curing conditions.

The requirement for temperature monitoring may be waived by the Structural Concrete

Engineer if the concrete is not subject to accelerated curing and ambient temperatures are

expected to be well in excess of 40°F throughout the duration of production.

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hour curing procedure described in Subsection 510.09(a), in accordance with the requirements of

PCI MNL-116, Section 4.19 and the following:

fresh concrete to attain a compressive strength of 500 psi.

Testing to determine the time of set shall be done when the concrete temperature is within

± 5°F of the anticipated concrete placement temperature.

Alternately, time of set may be found by taking a minimum of three different concrete

temperatures at intervals of approximately 10°F, entering that data on a graph, and then

drawing a best-fit smooth curve line through the three data points. This graph will be used

to determine the time of set for the anticipated concrete placement temperature, rounded

up to the nearest half hour.

structure component, an enclosure that is suitable for containing live low-pressure steam

or heat shall be placed over the forms. The fabricator shall make these enclosures available

for inspection prior to casting.

shall be taken to prevent the live steam from being directed on the concrete or forms in

such a way as to cause damage from localized high temperatures.

covered with plastic sheeting. Radiant heat may be applied by means of circulation pipes

containing steam, hot oil, or hot water, or by electric heating elements.

increased at a maximum rate of 10°F per hour. However, the temperature within the

concrete shall not be more than 40°F higher than the initial concrete placement temperature

or more than 104°F, whichever is less.

Following the initial set, the internal concrete temperature shall be increased at a rate of

not more than 40°F per hour until the desired curing temperature is reached. The maximum

internal concrete temperature shall not exceed 160°F. The maximum differential between

the curing enclosure temperature and internal concrete temperature shall not exceed 40°F.

The selected curing enclosure temperature range shall be as approved on the fabrication

drawings.

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The accelerated curing cycle shall be considered complete when the method of supplying

heat is stopped or the concrete temperature drops below 120°F. Two concrete cylinders

shall be tested immediately upon completion of the accelerated cure cycle.

The maximum cooling rate from the sustained accelerated curing temperature shall be 50°F

per hour. Cooling at this rate shall continue until the concrete temperature is 40°F or less

above the ambient temperature outside the curing enclosure.

additionally wet-cured until this strength threshold is met. If the precast concrete has

attained 80% of its 28-day strength during the accelerated curing cycle, no further curing

will be required.

be exposed to cold weather conditions as defined in Subsection 510.08(o) shall be allowed to cool

and dry in an environment of at least 40°F for 24 hours to prior to exposure to cold weather

conditions. For pieces cast outdoors in cold weather ambient conditions, all requirements of

Subsection 501.07(b) shall apply.

100 feet of production length. The Structural Concrete Engineer may require that additional

temperature recorders be installed if it is determined that the one per 100 feet of production length

spacing does not allow for adequate monitoring of the curing conditions.

Temperatures recorded on the data logs shall be used to determine whether the prestressed concrete

structure components have been cured in accordance with the specifications and the approved

fabrication drawings.

The recorder shall record, at intervals not to exceed 15 minutes, the temperature of the air

surrounding the piece as well as the internal concrete temperature. Temperature recording shall

continue until completion of the chosen curing method.

Each recorder’s data log shall indicate the casting bed, the date of casting, the start and finish times

of record, and the mark number of the prestressed concrete structure component being cured. At

the completion of the temperature recording period, the data logs shall be given to the Agency

representative.

Recorder accuracy shall be certified at least once every 12 months, and the certificate displayed

with the recorder. Calibration and certification shall be performed by either the manufacturer, the

supplier, or an independent laboratory. Random temperature checks of each recorder may be made

by an Agency representative.

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510.10HANDLING, STORAGE, AND SHIPPING. Handling and installation of prestressed members

shall be performed with members in an upright position and with points of dunnage support and direction

of lifting reactions as specified in the approved lifting calculations.

Prestressed concrete shall be handled, stored, and shipped in such a manner as to minimize chipping,

cracks, fractures, discoloration, and excessive bending stresses. Units damaged by handling, storage, or

shipping shall be replaced at the Contractor’s expense.

Prior to shipment of any members, all NCRs shall be resolved and all required testing shall demonstrate

that the design requirements have been met.

510.11INSTALLATION

prestressed concrete member erection shall be of adequate design and capacity to safely

erect, align, and secure all members and components in their final positions without

damage. The Contractor is solely responsible for the methods and equipment employed for

the erection of the prestressed concrete member.

Construction drawings for prestressed concrete member erection shall be submitted in

accordance with the requirements of Subsection 105.06. The erection plan shall include the

methods and sequence of prestressed concrete member erection, temporary bracing

requirements, the equipment to be used for the erection, and the necessary computations to

demonstrate that all of the erection equipment has adequate capacity for the work to be

performed.

The erection plan shall also include provisions for all stages of construction, including

temporary stoppages. When the fabricator-designed lifting hooks will be used by the

Contractor, computations indicating the magnitude of stress in the segments during

erection are not required, unless otherwise ordered by the Engineer.

The prestressed concrete members may be used for support of equipment prior to

placement of the deck only with written permission of the Engineer. The proposed use of

the prestressed members for support of equipment shall be detailed in the erection plan.

Submittal of the erection plan is for documentation purposes only and shall in no way be

construed as approval of the proposed method of erection. The Contractor shall follow the

erection plan as submitted.

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and tension them to 3.0 kips.

required for fairing out any unevenness between adjacent units. Type IV mortar shall be

used, and grout placement shall occur at the same time mortar is placed to fill shear keys

between members and in accordance with the requirements of Subsection 510.12.

The mortar shall be placed to eliminate unevenness, forming a smooth surface from the

higher beam edges to the lower surface. The finished surface shall be feathered smoothly

and be free of depressions or sharp edges.

of Subsection 510.13.

shall be attached to the top of the flange of the girder with an adhesive, approved by the

Engineer, in accordance with the manufacturer’s recommendations.

The temporary supports shall be cut in the field to the required height after the blocking

depth has been determined. The bottom of the panels shall be a minimum of 1 inch above

the top of the top flange of the girder.

panels, until the top slab is cast and cured. Construction loads on individual panels shall be

uniformly applied and shall not exceed an average loading of 40 pounds per square foot.

the ends of the panels and over the girder flanges up to the bottom of the panels shall be

completely filled with the material specified on the Plans.

Temporary supports and grout dams for prestressed deck panels shall consist of continuous

strips of high density, extruded polystyrene insulation board with a minimum compressive

strength of 60 psi.

510

If leveling screws are used, polyethylene foam with a density of 1.7 pcf shall be employed

as a grout dam. Prior to placement of the cast-in-place deck, the concrete shall be wet cured

until a minimum of 85% of f′c is attained by the average strength of two field-cured

concrete cylinders. The leveling screws shall be completely removed and the holes filled

with grout prior to the placement of deck concrete.

with full bond to the panels shall be removed by an approved method.

510.12GROUT

roughened in accordance with the Plans. The surface to be grouted shall be thoroughly wetted, yet

free of all standing water. Shear keys shall be saturated surface dry prior to grouting.

level screw voids, and for fairing joints as detailed in the Contract or as ordered by the Engineer.

Grout shall be Type IV mortar in accordance with Subsection 707.01(e)(1). Additional aggregates

shall not be added to the material during field mixing.

Ready mixed mortar in accordance with Subsection 707.01(e)(2) may be substituted with written

permission of the Engineer. Placement of ready mixed mortar shall be complete within 90 minutes

of the time of batching.

The Contractor shall submit a proposed grouting procedure to the Engineer for their review and

approval. The proposed grouting procedure shall include the required equipment, workforce,

manufacturer’s product data sheet for prepackaged mortar or the approved mix design of the ready

mixed mortar when approved, placement rate, batch size, and all necessary details to explain how

the grouted element will be placed in accordance with specification and manufacturer

recommendations, as applicable, without air voids or cold joints.

Post-tensioning may occur when a field cured sample demonstrates conformance with post-

tensioning strength requirements specified in the Contract, as determined in accordance with

ASTM C109. Three cubes shall constitute a single sample.

recommendations and shall be readily pourable so that it completely fills the shape of the shear

keys or holes, depending on the product being installed. The placement of the grout for each shear

key shall be continuous. The grouting of each shear key shall be completed in its entirety within a

single working day.

510

cured for not less than 3 days by the wetted burlap method in accordance with the requirements of

Subsection 501.15. Curing shall commence immediately following completion of grouting of

individual shear keys.

510.13POST-TENSIONING. Post-tensioning strands shall not be bonded to the concrete and shall be

protected against corrosion as specified in the Contract.

Post-tensioning of strands shall not commence until a minimum compressive strength of 1,500 psi has

been attained in the grout, when tested in accordance with the requirements of Subsection 510.12(b). If

the design strength is met prior to completion of the required curing, the grout cure shall be maintained

during the post-tensioning operation.

Strands shall be stressed in the following sequence:

tension. Stressing shall begin by pulling the inner-most strands first, then proceeding

symmetrically towards the member’s ends.

In the case where the Plans call for top and bottom strands, the sequence shall be followed using an initial

pull of 15.0 kips, top and bottom, followed by a sequence using the final design tension.

No loading of elements shall be allowed until post-tensioning is completed.

510.14METHOD OF MEASUREMENT. The quantities of Prestressed Concrete Box Beams,

Prestressed Concrete Voided Slabs, Prestressed Concrete Girders, Prestressed Concrete Solid Slabs and

Prestressed Concrete NEXT D Beams to be measured for payment will be the number of linear feet of the

types and sizes of prestressed concrete members used in the complete and accepted work.

The quantity of Grouting Shear Keys to be measured for payment will be the number of linear feet of

grouted shear keys in the complete and accepted work.

The quantity of Prestressed Concrete Deck Panels to be measured for payment will be the number of

square feet of prestressed concrete deck panels used in the complete and accepted work.

510

510.15BASIS OF PAYMENT. The accepted quantities of Prestressed Concrete Box Beams, Prestressed

Concrete Voided Slabs, Prestressed Concrete Girders, Prestressed Concrete Solid Slabs, and Prestressed

Concrete NEXT D Beams will be paid for at the Contract unit price per linear foot for the types and sizes

of prestressed concrete members specified.

The accepted quantity of Prestressed Concrete Deck Panels will be paid for at the Contract unit price per

square foot.

Payment will be full compensation for detailing, fabricating, repairing, sandblasting, quality control

testing, transporting, handling, and installing the materials specified, including the concrete,

reinforcement, prestressing steel, transverse ties, enclosures for prestressing steel, anchorages, mortar, and

anchor rods. Payment will be full compensation for any other material contained within or attached to the

members, for furnishing and implementing the erection plans, and for furnishing all labor, tools,

equipment, and incidentals necessary to complete the work.

The Engineer may authorize partial payments in the following manner:

been approved by the Agency.

when the prestressed elements have met the requirements of Subsection 540.09 for shipping.

The accepted quantity of Grouting Shear Keys will be paid for at the Contract unit price per linear foot.

Payment will be full compensation for providing all materials and performing the work specified herein,

and for furnishing all labor, tools, equipment, and incidentals necessary to complete the work.

Any other grouting work, such as fairing out unevenness between adjacent units and filling leveling screw

holes, transverse anchor recesses, and dowel holes, will be considered incidental to the work for

prestressed concrete members.

510

Payment will be made under:

Pay Item Pay Unit

510.2100 Prestressed Concrete Box Beams..............................................................Linear Foot

510.2200 Prestressed Concrete Voided Slabs ...........................................................Linear Foot

510.2300 Prestressed Concrete Girders ....................................................................Linear Foot

510.2400 Grouting Shear Keys .................................................................................Linear Foot

510.2500 Prestressed Concrete Solid Slabs ..............................................................Linear Foot

510.2600 Prestressed Concrete NEXT D Beams ......................................................Linear Foot

510.4000 Prestressed Concrete Deck Panels ............................................................Square Foot

511

5-165SECTIO N 511 – REMOVAL, CONTAINMENT, AND DISPOSAL OF LEAD PAINT

511.0 1 DESCRIPTION . This work shall consist of the washing of the existing lead paint coated surfaces, the removal of existing lead paint and grease rustproofing compounds, as well as the containment, collection, temporary storage, transportation, and disposal of the resulti ng waste. Waste requiring containment and control includes, but is not limited to, old paint, spent abrasives, corrosion products, mill scale, dirt, dust, grease, oil, salts, solvents, and water used for cleaning the surface of existing lead coatings. Are as of paint removal operations shall be as indicated on the Plans. 511.0 2 GENERAL REQUIREMENTS . The existing coatings are assumed to contain lead and other toxic metals, regardless of any test results. All removal activities will be performed accordingl y. This specification provides the requirements for containment and for the protection of the public and the environment from exposure to harmful levels of toxic metals that may be present in the paint being removed or repaired. The Contractor shall take reasonable and appropriate precautions to protect the public from the inhalation or ingestion of dust or debris from the operations, and is responsible for the clean -up of all spills, releases, or emissions of waste at no additional cost to the Agency. The Contractor shall comply with the requirements of this specification and all applicable federal, state, and local laws, codes, and regulations. These include, but are not limited to, the regulations of the U.S. Environmental Protection Agency, Vermont Occu pational Safety and Health Administration (VOSHA) , Vermont Department of Health, and the Vermont Agency of Natural Resources. The Contractor shall comply with all applicable regulations even if the regulation is not specifically referenced herein. If a federal, state, or local regulation is found to be more restrictive than the requirements of this specification, the more restrictive requirements shall prevail as determined by the Engineer. 511.0 3 PROJEC T CLASSIFICATION . The removal, containment and disposal of lead paint will be classified as either a Type I or a Type II project as follows:

existing structure, or to remove the paint from large, con tiguous areas of a portion of a structure. Examples of such work would be projects where all or some of the main girders were completely stripped of paint. Often, paint removal and repainting the structure will be a primary goal of a Type I project. Type I projects can usually be expected to require a full external containment system.