04 bvt prestressed girderok

SECURITY AND SAFENESS GMS Ben Luc Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 CONSTRUCTION METHOD STATEMENT FOR PRODUCTION OF PRESTRESSED CONCRETE GIRDERS TABLE OF CONT[.]

CONSTRUCTION METHOD STATEMENT FOR PRODUCTION OF PRESTRESSED CONCRETE GIRDERS

TABLE OF CONTENTS

I PRESTRESSED CONCRETE

II CONSTRUCTION METHOD FOR SUPER TEE GIRDERS

III CONSTRUCTION METHOD FOR PCI 33m GIRDERS

I PRESTRESSED CONCRETE

1 Material requirements

1.1 Reference standards

AASHTO M235 Epoxy Resin Adhesives

22TCN 272-05 Specification standard for Bridge design

AASHTO LRFD Bridge Design Specifications, Deflection Criteria for GirdersASTM A421-91 Un-coated Stress Relieved Steel Wire for Pre-stressedConcrete; ASTM A416-99 Steel Strand, Un-coated Seven Wire Stress Relieved Strand for

Pre-stressed Concrete

ASTM A722M-07 Uncoated High Strength Bars for Pre-stressing Concrete 22TCN 247-98 Construction and Inspection of pre-stressed RC bridge girderTCVN 9114:2012 Product of pre-prestressed concrete – Technical specificationand acceptance

1.2 Material for prestressed concrete

1.2.1 Prestressing steel

High tensile strength steel wire shall be stress relieved and shall conform to therequirements of ASTM A421-91 or equivalent for Un-coated Stress Relieved SteelWire for Pre-stressed Concrete

High tensile steel strand with low-relaxation shall be weld free and stress relievedafter stranding and shall conform to the requirements of ASTMA416-99 or equivalentSteel Strand, Un-coated Seven Wire Stress Relieved Strand for Pre-stressedConcrete

High strength steel bars shall confirm to the requirements of ASTMA722M orequivalent for Uncoated High Strength Bars for Pre-stressing Concrete

Testing of pre-stressing reinforcement shall be in accordance with the requirements

of the ASTM Specifications for the type of system intended to be used or subject toapproval by the Engineer

1.2.2 Anchorages for post tensioning

All anchorage assemblies shall be subject to the approval of the Engineer

All post-tensioned pre-stressing steel shall be secured at the ends by means ofapproved permanent type anchoring devices The Contractor shall submit informationand details, including test certifications for by the Engineer.

End anchorage devices (stress and dead anchors) shall be designed and manufacturedfor the types of tendons to be used They shall have a previous service record ofperformance and durability when used on similar type work

All anchorage devices for post-tensioning shall be capable of holding the stressing steel at a load producing a stress of not less than 95 percent of theguaranteed minimum tensile strength of the pre-stressing steel

pre-Fixed anchorages for tendons in pre-cast beams shall be of steel bearing plate typewhile all remaining anchorages shall be those capable of adjustment by means of athreaded anchor head and ring nut

It shall be the responsibility of the Contractor to confirm the required burstingreinforcements in the local zone for the particular shape and design of the anchoragedevices proposed

All externally exposed steel parts shall be protected from corrosion All threadedparts and fittings shall be protected by greased wrappings or plugs until used.Anchorages shall be kept free from dirt, mortar, loose rust or other deleteriousmaterials Damaged anchorage parts shall not be used

1.2.3 Ducts

Ducting for internal tendons shall be fully compatible with the proposed pre-stressingsystem The ducts shall be fabricated from corrugated galvanized sheet steel orcorrugated thick-walled HDPE conduit

Minimum duct thickness shall be as follows:

- 26 gauge for duct diameter less than or equal to 67mm

- 24 gauge for duct diameter greater than 67 mm

- 31 gauge for bar tendons

Ducts shall have grouting connections at each end and shall have vent/drains at allintermediate high and low points, subject to the approval of the Engineer

1.2.4 Grout for ducts

Unless otherwise specified in other prevailing sections or subject to approval by theEngineer as a result of grouting trials, the grout shall:

- Consist only of ordinary Portland cement, water and expansive admixtures

approved by the Engineer and used in accordance with the manufacturer’sinstructions;

- Have a water to cement ratio a slow as possible consistent with the necessary

work ability, and under no circumstances shall the water/cement ratio exceed0.40;

- Not contain admixtures containing chlorides, nitrates or similar electrolytic

The maximum size of aggregate for use in the manufacture of pre-stressed concreteshall be 25 millimetres

The main properties of concrete such as compressive strength after 28 days, Modulus

of Elasticity (Young Modulus), and other properties that were used for the detaileddesign shall be confirmed by testing of samples of the approved mix design TheContractor shall perform the tests in accordance with the appropriate standards, or asmay be required by the Engineer

II CONSTRUCTION REQUIREMENTS

The Contractor shall assign an experienced technician, skilled in the use of stressing system, who shall supervise the work being performed in compliance withthese specifications and to the satisfaction of the Engineer

pre-Vertical alignment and girder lengths shown on the drawings represent dimensions atthe time of final creep Deflection criteria for girders shall be in accordance with22TCN272-05, longitudinal deflections may be rectified by an appropriate approvedmethod

1 Placing steel

All steel reinforcement shall be accurately placed in the position shown on thedrawings and rigidly held in place during placing and setting of the concrete Distancefrom the forms shall be maintained by stays, formwork spacers, ties, hangers, or otherapproved support Formwork spacers for holding units from contact with the formsshall be of approved material, shape and dimensions Layers of reinforcement shall beseparated by suitable wire spacers Wooden blocks shall not be used

2 Pretensioning method

A record shall be kept of the jacking forces and the elongations produced and theminimum age in hours of the concrete for each unit until the time the tendons werereleased

No bond stress shall be transferred to the concrete, nor shall end anchors be released,until the concrete has attainted a compressive strength of not less than 85% of thespecified 28-day strength as shown by standard specimens cured in a similar fashion

to the element The elements shall be cut or released in such an order that eccentricity

of pre-stress is minimized subject to the approval of the Engineer

3 Post-tensioning method

Post-tensioning shall be carried out in accordance with an approved method, with anapproved control method, and in the presence of the Engineer unless permission hasbeen obtained to the contrary

Immediately before tensioning, the Contractor shall prove that all tendons are free tomove in the ducts

Each anchorage device shall be set square to the line of action of the correspondingpost-tensioning tendon and shall be securely fixed in position and gradient to preventmovement during the placing and compaction of concrete

Except where dead-end anchorages are cast in the concrete, tendons shall not beinstalled until just prior to stressing Tendons shall be pulled or pushed through theduct in such a manner as to avoid damage to either the tendon or the duct

The Contractor shall establish the datum point for measuring extension and jackpressure to the satisfaction of the Engineer Allowance shall be made for the friction

in the jack and anchorage for pull-in of the tendon during anchorage

The tendons shall be stressed at a gradual and steady rate until the required extensionand tendon load are reached or are approved by the Engineer The sequence ofstressing shall be as shown on the drawings or directed by the Engineer

The force in the tendons shall be obtained from readings on a load cell or pressuregauge incorporated in the equipment and the extension of the tendons measured Theextension of the tendons under the approved total forces shall be within the limitsgiven below of the agreed calculate dextension

Transverse Tendons for Segments: ±10%averagefor one tendon

±7%for average of one segmentLongitudinal Tendons for Segments ±5%

If the measured extensions are not within the specified tolerance then the Contractorshall submit to the Engineer his method of rectifying the discrepancy

When the pre-stressing force has been applied to the satisfaction of the Engineer, thetendons shall be anchored The force exerted by the tensioning apparatus shall then

be decreased gradually and steadily so as to avoid shock to the tendon or anchorage

Full records shall be kept of all tensioning operations including measured extensions,pressure gauge or load cell readings and draw-in at anchorage Copies of recordsshall be supplied to the Engineer within 24 hours of each tensioning operation.

A check shall be made of pre-camber and if significantly different to the calculatedvalue, the Contractor must investigate before construction of further girders

Unless otherwise agreed by the Engineer, tendons shall not be cut less than 2 daysafter stressing

4 Grouting

4.1 Plant for grouting

The grout mixer shall produce a grout of colloidal consistency The grout injectorshall be capable of continuous operation with a sensibly constant pressure up to 0.70-N/mm2 and shall include a system of circulating or agitating the grout whilst actualgrouting is not in progress All baffles to the pump shall be fitted with 1.18 mm sievestrainers

The equipment shall be capable of maintaining pressure on completely grouted ductsand shall be fitted with a nozzle that can be locked off without loss of pressure in theduct

The pressure gauges shall be calibrated before they are first used in the Works, andthereafter as required by the Engineer All equipment shall be thoroughly cleaned andwashed with clean water at least once every 3 hours during the grouting operationsand at the end of use for each day

During the grouting operation, the Contractor shall provide adequate flushing-outplant to facilitate complete removal of the grout in the event of a breakdown of thegrouting equipment or other disruption before the grouting operation has beencompleted

4.2 Grouting of ducts and sheathing

Grouting trials shall be undertaken when directed by the Engineer Prior to using thegrout in any trial or in the works the Contractor shall submit a detailed methodstatement for grouting procedures covering proposed materials, sheathing, anchorageand vent alignment equipment, and quality control to the Engineer for his approval.All ducts shall be thoroughly cleaned out by means of flushing with water and/orwater/compressed air

Grouting of ducts shall be carried out as soon as it is technically practicable, but notmore than 4 weeks after the tendons inside the ducts have been stressed, and theEngineer’s permission to commence grouting has been obtained If due to therequirements of the stressing procedure, tendons cannot be grouted within 4 weeksthe sheathing shall be sealed to protect the tendons from corrosion

Injection shall be continuous and slow enough to avoid producing segregation of thegrout The method of injecting grout shall ensure complete filling of the ducts andcomplete surrounding of the steel Grout shall be allowed to flow from the free end ofthe duct until its consistency is equivalent to that of the grout injected The openingshall then be firmly closed Any air vents shall be closed in a similar manner oneafter the other in the direction of flow The injection tubes shall then be sealed offunder pressure until the grout has set.

The filled ducts shall not be subjected to shock or vibration within 1 day of grouting.Not less than 2 days after grouting the level of grout in the injection and vent tubesshall be inspected and made good as necessary

The Contractor shall keep full records of grouting including the date when each ductwas grouted, the proportion of the grout and any admixtures used, the pressure,details of any interruptions and topping up required Copies of these records shall besupplied to the Engineer within 3 days of completing grouting

4.3 Protection of prestressing anchorages

As soon as possible after tensioning and grouting are completed, exposed endanchorages, strands and other metal accessories shall be cleaned of rust, misplacedmortar, grout and other such materials

Immediately following the cleaning operation the entire surface of the anchoragerecess and all exposed metal shall be thoroughly dried and uniformly coated with anepoxy bonding agent conforming to AASHTO M235 Class III in accordance with themanufacturer’s recommendations

The anchorage recess shall then be filled with an approved non-shrinkage mortar.The mortar shall not contain aluminium powder, iron particles, chlorides, sulphates,fluorides or nitrates

Where the protection will form part of the exposed works, the anchorage recess shall

be filled with concrete of the same quality and colour as that of the adjacent concreteand shall be applied and cured in accordance with these specifications or as may berequired by the Engineer

5 Curing

Except as specified here in or otherwise approved, wet (water) curing shall beprovided in compliance with the requirements in Specification-Concrete andConcrete Structures If the Contractor elects to cure by any other method, the methodand details shall be subject to the approval of the Engineer

6 Handling, transport and storage

Pre-cast pre-stressed concrete shall not be moved from the casting position, ortransported, until the concrete has attained a compressive strength of 90% of thespecified 28-day strength

Extreme care shall be exercised in handling and moving concrete members.

Pre-cast girders and slabs shall be transported in an upright position, shock shall beavoided and the points of support and directions of the reactions with respect to themembers shall be approximately the same during transport and storage as when themembers is in its final position If the Contractor deems it expedient to transport orstore pre-cast pre-stressed units in other positions than this, it shall be done at hisown risk after notifying the Engineer of his intention to do so Any unit considered

by the Engineer to have become substandard shall be rejected and replaced by anacceptable unit at the Contractor’s expense

7 Marking of precast prestressed members

Each precast prestressed member shall be uniquely and permanently marked so as toshow its type and date of casting

III CONSTRUCTION METHOD FOR SUPER TEE GIRDER

1 Number of Tensioning pedestals and formwork

SUPER-TEE beams are the pre-stressed concrete beams The prestressing strand willstressed released on the tensioning pedestals When the concrete beam has reached85% required strength to conduct cutting prestressing strand so as to produce stress inthe prestressing strands and concrete of beams

External and inner formworks and shuttering of steel hangers, steel beams and innerformwork shall be fabricated in two sets for each

2 Design of tensioning pedestals and formworks

2.1 Pre-stressed tensioning pedestals

Structure of tensioning pedestals to ensure convenience for placing reinforcing steeland pre-stressing steel to ensure adequate and convenient space for the erection andremoval of formwork, concrete supply, placing concrete and lifting casted beamsthen promptly transport to the storage platform

The position of the tensioning pedestal must be in high places to ensure gooddrainage, the tensioning pedestal to ensure absolutely no settlement

- After the installation of vibrator into the side formwork is complete, trial

operation is needed to check the stiffness of the formwork, the state ofelimination of the lateral force of the vibrators

- Technical requirements of formwork:

 The firmness, durable, airtight

Pouring concrete to create even surface for casting pedestal

Segmental construction of the tensioning pedestal by "a step by step method" meansconcreting the bottom and side walls of each section from this end to the other end ofthe tensioning pedestal

At construction joints, reinforced steel shall be overlapped 30-40 d

The right in place buried details in the tensioning pedestal to link between tensioningpedestal and jacking beam, link the pedestal with internal formwork while installingthem on pedestals before pouring concrete to determine the exact location

After placing concrete tensioning pedestal, curing of concrete takes at least for aperiod of 7 days

3.2 External formwork

Manufactured to full designed length and size At junctions, the connected details arefilleted 45o and connected by butt welding, and then grinding welds smoothly.Welding process to link all details shall comply with the order of welding technologyand avoid warping

After welding done to check the detailed dimensions and flatness of each individualplate, fix the error before installing the tensioning pedestal

3.3 Inner formwork

Processing of the middle and the border frames and stiffeners To avoid warping, theframe is processed in the fabricating mold Inspection of detailed dimensions for eachframe

Link the frames together by longitudinal bracing frames Check the overall size of theframe Resetting to ensure permitted tolerance

Check the overall size of the entire inner formwork

Installing the vibrators to the frame by bolts with lock washer

The steel plate covered on the top of the frame is arranged to be able to get inside toinstall the vibrator as well as checking and maintenance of vibrators during use.

4 Installation of external formwork with tensioning pedestals

Each plate of the external formwork is linked with tensioning pedestal, may placeand pump cement grouting linking for each section before the joint welding and thenpumping cement grouting for the next section, or put the entirely then pumpingcement grouting The sequence of construction as follows:

- After fabrication of the external formwork plate meets the requirements then

each plate will be installed on the tensioning pedestal Link all externalformwork plates by butt weld then grinding welds smoothly Use theturnbuckles to tighten the external formwork with the tensioning pedestal.Check the overall size of the external formwork installed

- Pumping cement mortar into the gap between the external formwork and the

tensioning pedestal

- Repeat the above sequence of construction for the next segment

 Set and associate support structures for wall wing together withtensioning pedestal

 Set and associate jacking beam with the tensioning pedestal

 Check the overall size of the entire external formwork with tensioningpedestal

5 Installation of inner formwork

Inner formwork is only installed when the steel frame and cable have been put inplace and prestressed cable has been stress released

Inner formwork is installed support system parallel to the upper surface of thetensioning pedestal Before installation of the sections of formwork inside steelcages, it is needed to check, measure size, and apply release agent

Use a steel girder to lift the sections of the formwork sections Measuring andadjustment of cross-arm supporting formwork to ensure size

6 Girder and beam fabrication yard

Fabrication yard should have a suitable length Beam and girder fabrication yard arecompacted to K95 The beams are chocked with concrete sleepers

Moving or transfering girders from casting pedestal to stock yard by gate gantry, withthe lifting

7 Checking, inspection and removal of formwork

7.1 Checking formwork, scaffolding for tensioning pedestal

The stages during the construction process is supervised and inspected by thetechnician.

Formwork, scaffolding for the tensioning pedestal should be checked carefully beforeplacing concrete as well as in the process of placing concrete Promptly repair thedamage

While tensioning of the prestressed steel wire on the tensioning pedestal to check thedeformation and displacement of the tensioning pedestal as well as all associatedparts, welds to ensure safety and quality of tensioning work as well as the loss ofstresses in the prestressed steel wire

7.2 Removal of formwork and scaffolding

The inner formwork shall be removed after 36h of placing concrete

8 Fabrication of reinforcing steel

8.2 Febrication of reinforcing steel

Reinforcing steel cage is processed at the site on the support system

Longitudinal joints are staggered how on a cross-section quantity of the joints of

Place the drainage pipe at the position of the end sealing by the seal PVC pipe

Concrete spacers are tied with the reinforcing steel cage, the concrete strength of theconcrete spacer is equal to or greater than the strength of concrete beams

8.3 Fixing reinforcing steel into the formwork

Prior to installation of reinforcement cage, surface of the external formwork must becleaned and the release agent is applied to ensure that the lifting of the beams from theformwork is easy

Use a long enough beam and two lifting hooks of the gate gantry to lift the entirereinforcement cage from the fabrication platform to the tensioning pedestal and placeinto formwork.

Check the reinforcement cage while placing into the formwork, the straightness of thesteel strand, thickness of protective coats of reinforcement

Installation of formwork for head beam The steel strand is threaded through the holes

of the head beam shuttering and the jacking beam, make sure the steel strands arevertical alignment from this end to the other end, the high strength steel strands are nottwisted or cross interlaced

9 Tensioning prestressed steel

9.1 Allowable tolerance for fabrication of concrete for beam casting pedestal.

The Contractor shall provide sufficient anchorage certification of the manufacturer.Check the anchor shackles and anchor keys before producing stress

9.2 Preparation work before producing stress

Check the defect of formwork beams, tensioning pedestals if that affects the loadcapacity, the repair shall be conducted

Check the test results of high tensile strength tendon

Check the technical certification of the anchorage

Check the tolerance when placing high tensile strength tendon

Check and adjustment of the tensioning devices (prestressed jacks), the pressure gaugewill be used If beyond the time limit must be re-examined

Determination of friction coefficient of the jack and anchorage shackle (determinedseparately for each jack)

Check the threaded hole for high tensile strength steel tendon (purity, the smoothness).Check the operation and safety procedures

9.3 Installation of high tensile strength strand.

High tensile strength strand is prepared on the tensioning pedestal, ensure the tightnesswhen tensioning, forming shapes of straight strands The strands need to be preservedfrom rust due to the moisture from the air Do not adhere oil, grease, and dirt, do notlet the stand deformed or chafed

9.4 Threading anchorage shackle.

Before inserting an anchorage shackle into the tendon to prepare tensioning stressed tendons, it is needed to clean soil, sand and fat protective layer of tendon andanchorage shackle For the anchorage core prior to connecting to anchorage, greaseshall be get rid of absolutely until clean dry surface

pre-9.5 Tensioning device and sequences for tensioning:

Jacks used to tension the tendon is single wire tensioning jack

Use anchorage

Jacks and anchorage must be tested before being put into use

When tensioning, the tendons are tensioned by a single strand, the strand is tensionedfrom both ends Tensioning sequence as in accordance with design method

9.7 Technical requirements of the process of tensioning prestressed tendons

Before tensioning, check the structure of tensioning pedestal carefully, horizontalbeams and tensioning devices

When installing prestressed tendon, to avoid dirt into reinforced

Deviation of the position of tendon after being tensioned compared with the designdoes not exceed 5 mm

10 Concrete works

Concrete is produced by batching plant at construction sites and are transported to theconstruction location by agitators Prior to delivery of concrete, the quality control andtesting of concrete must be conducted along with delivery records

With different structures: measures for placing concrete are shown in the drawings ofthe construction methods

10.1 Components of concrete

Adjusting concrete components at the site: Adjusting concrete components at the siteare conducted on the principle that does not change the water / cement ratios of design

concrete component When moist aggregates should reduce the amount of mixingwater, keep the required slump.

10.2 Manufacture of concrete mix

Manufacturing concrete mix by batching plant (or concrete mixer) Mixing concreteprocess shall comply with the following provisions:

- When mixing concrete, materials must be weighted accurately Moisture

content of sand and stones must be conducted inspection regularly to adjust theamount of aggregates and water use

- Cement, sand, macadam and liquid admixture to make concrete mix is

weighted by volume Water and admixture weighed by volume Allowedtolerance when weighing shall not exceed the allowed values

- The accuracy of measuring equipment must be calibrated prior to placing

concrete During weighing, regular monitoring to detect and correct promptly

10.3 Transportation of concrete mix

The transportation of mixed concrete from the batching plant to the work should ensurethe following requirements:

- Use a reasonable means of transport, to prevent the concrete mixture from

segregation, loss of cement grout and water loss from wind and sun

- Using the equipment, manpower and transportation should be arranged to suit

the volume, speed of mixing, pouring and compacting concrete

- Allowable time to keep the concrete mix during transport should be determined

by experiments on the basis of weather conditions, type of cement andadmixture used

10.4 Placing concrete

When placing concrete must meet the following requirements:

- Closely monitor the status of formwork during the construction process to

settle in time if problems occur

- When it rains, measures to cover in order not to let the rain water into the

concrete

- Only to place concrete when the ambient temperature satisfying the

requirement

- Concrete was placed in layers with a thickness not exceeding 60cm and ensure

concrete is placed shall be able to bond with the next placing concrete layer.Placing time between layers does not exceed the initial setting time of theconcrete

- The placing concrete: for each type of structure, placing concrete can be used

cranes or pumps (details shown in the drawings).

Notes when compacting concrete:

- When using poker vibrators, moving distance not exceeding 1.5times the

radius of the vibrator effects Distance to side formwork from5-10cm,penetrating in to the under concrete layer 5-10cm, when finishing eachvibration of a place just to with draw vibrator up, avoid collision of vibrator in

to formwork, reinforcing steel and right in place buried parts

- When using the vibrator must base on the figure and shape of the structure and

vibrator functions, through testing to determine the distance of the vibrators

- When the concrete to stop subsidence, no air bubbles, surface well-compacted,

then stop vibrating

The placing concrete must be conducted continuously If interruption occurs, theinterupption time must be less than the time of initial setting, or less than the allowabletime for re-vibrating the earlier placed concrete

During a allowabel interuption time, it must be tested to determine, usually in theprocess of pouring concrete the interuption time is not more than 45 minutes

After completion of the placing concrete and concrete is in the stage of initial setting ifthe surface exposes shall promptly repair and screed smoothly Wait untilsedimentation of the grout, scread the second time and and finishing or roughening thesurface

During the placing concrte shall regularly check the stable status of the supports,formwork, reinforcing steel and right in place buried components If found loose,deformed, displacement must settled timely

10.6 Curing concrete

After placing conrette, concrete must be cured in conditions of humidity and neededtemperature for curing and preventing the harmful effects during curing of theconcrete

Moisture curing: is the process for keeping concrete with moisture necessary to thesetting and hardening after shaping During curing, the concrete shall be protectedagainst mechanical impacts such as vibration, shock forces, loads and impacts, whichare likely to cause other damage

10.7 Checking of the concrete samples

The limit compressive strength of concrete must be taken through testing samples todetermine the standards of current regulations Each casted beam takes 09 samples, 03samples tested after 72 hours (3 days), 03 following samples is pressed after 7 days, 03remaing samples to determine the remaining 28-day strength The testing sample ofcylinder 150x300 mm or cube 150x150x150 mm

The quality of materials used for mixing concrete must be tested, the experimentalmethods must conform to the relevant regulations

11 Cutting the tendons and measuring camber of the beams

To only conduct the cutting tendon to transfer the tensioning force to the concretewhen the concrete of girder reaches the required strenth as in accordance with thetechnical specification

Before cutting strand, paint markers shall be marked on every strand at both ends ofthe beams, away from outer surface of the formwork about 15 cm to measure thelagging of strand inside the beams at each end The sections of the shuttering of thebeam and the formwork is moved out of the concrete beams

The sequence for cutting strand is conducted simultaneously from the inside to outsideand and symmetric to the beam alignment The strands are cut each individual strandand simultaneously at both ends by cutting tools in position in the jacking beam ofabout 30 cm

Measuring the camber on the surface of concrete beam along the beam alignmentwhen the prestressed strand has been cut Marking paint track to observe the camber atthe these positions Alignment of the supports and wall bulkhead Using a levelingmachine to inspect the level for pre-cutting and post-cutting strand

Use a steel cutter to cut the head of steel strand how it levels to concrete surface in thehead beams Head of strand shall be applied the protective epoxy glue with thethicknees of at least 6 mm thick

12 Lifting girders out of formwork.

The lifting hook is inserted into the waiting bolts at both ends of each beam Gategantry will be used to lift beams out of formwork, shifting and placing beams to thestock yard

When lifting the beams out of formwork, beams should be further cured and keptmoisture until the end of day 7th

When completion of the works, conducting to repair the defects of the beam if any(small porous, uneven surface ) will be carried out immediately after lifitng out ofthe casting pedestal, but must be directed by the Engineer

The beams will be numbered and casting date on the beams at the same location