Precast Concrete Spec

7/27/2019 Precast Concrete Spec

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TABLE OF CONTENTS

1.0 GENERAL .............................................................................................................................. 2

1.1 Scope ........................................................................................................................................ 2

1.2 Definitions ................................................................................................................................ 21.3 Use of Language....................................................................................................................... 3

1.4 Work Included .......................................................................................................................... 3

1.5 Standards and codes of practice ............................................................................................... 3

1.5.1 Local Construction Specification ............................................................................................. 3

1.5.2 Project Specifications............................................................................................................... 4

1.5.3 British Standards ...................................................................................................................... 4

2.0 FABRICATION REQUIREMENTS .................................................................................... 4

2.1 Concrete production ................................................................................................................. 4

2.2 Placing of concrete ................................................................................................................... 4

2.3 Hot weather concreting ............................................................................................................ 42.4 Forms ........................................................................................................................................ 4

2.5 Reinforcement .......................................................................................................................... 4

2.6 Embedded items ....................................................................................................................... 5

2.7 Curing ....................................................................................................................................... 5

2.8 Accelerated hydration by heat treatment .................................................................................. 6

3.0 FINISHED PRODUCT REQUIREMENT .......................................................................... 7

3.1 Production tolerances ............................................................................................................... 7

3.2 Repairs ...................................................................................................................................... 7

4.0 ERECTION requirements ..................................................................................................... 7

4.1 Erection preparation ................................................................................................................. 7

4.2 Transient situations .................................................................................................................. 8

4.3 Lifting inserts ........................................................................................................................... 8

4.4 Lifting equipment and accessories ........................................................................................... 8

4.5 Joints and connections .............................................................................................................. 9

4.6 Sealants for joints ..................................................................................................................... 9

4.7 Maintenance of joints ............................................................................................................... 9

4.8 Erection safety .......................................................................................................................... 9

5.0 FACTORY AND SITE STORAGE ...................................................................................... 9

6.0 MARKING OF ELEMENTS .............................................................................................. 10

6.1 Marking Procedure ................................................................................................................. 10

6.2 Shop Marking ......................................................................................................................... 10

6.3 Packing Lists .......................................................................................................................... 10

7.0 TRANSPORTATION .......................................................................................................... 10

8.0 QUALITY CONTROL ........................................................................................................ 11

8.1 Shop Quality Control ............................................................................................................. 11


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8.2 Erection Quality Control ........................................................................................................ 11

1.0 GENERALThe considerations for design, manufacturing and erection of structural and non-

structural precast elements including joints and connections for buildings and buildingworks shall follow this specification.

1.1 ScopeThe intent of this specification is to cover the minimum requirements for the materials,

design, fabrication, supply and erection of all structural and non-structural precast

elements including joints and connections required for the construction of buildings andmiscellaneous structures as required, for the total completion of the project.

The work shall be in accordance with standards listed in this specification.

Before fabrication is started, checked shop drawings along with supporting designcalculations as applicable shall be submitted to, and be approved by, the COMPANY S

Engineer at least two weeks in advance. Drawings shall indicate all connections, details

and other pertinent data, erection plans and bills of materials. Location of holes andother connections necessary for attachment of work of other trades shall be properly

shown on the drawings.

1.2 DefinitionsThe following definitions apply:COMPANY xxxxxxxxxxx

CONTRACTOR xxxxxxxxxxxxx

SUB-CONTRACTOR The individual, partnership, firm or corporation qualified to

practice precast concrete works including testing under the

laws of the state, province or country in which the property for

the works lies, and is contractually obligated to perform the

specified services.

PROJECT xxxxxxxxxx

SHALL Denotes mandatory action or requirement

SHOULD Denotes an action or requirement which is not mandatory but

which is strongly recommended

SITE xxxxxxxxxxxx


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1.3 Use of LanguageThroughout this document the words 'will', 'may', 'should', 'shall' and 'must' when used

in the context of actions by CONTRACTOR, have specific meanings as follows:

Will is used normally in connection with an action by COMPANY, rather than by

CONTRACTOR.

May is used where alternatives are equally acceptable.

Should is used where a provision is preferred.

Shall is used where a provision is mandatory.

Must is used only where a provision is a statutory requirement.

1.4 Work IncludedThe work to be carried out by the SUB-CONTRACTOR shall include, but is not limited

to, the following:

Calculation and design drawing/preparation when not carried out by theCONTRACTOR.

Complete shop detail drawings with bills of material and inserts/ bolt schedules.

Erection drawings.

Supply and fabrication of all the items as required in specifications and/or drawings.

Erection of all elements together and any necessary temporary bracing duringerection.

Supply and install all bolts, including anchor bolts where required and erection boltswith nuts and washers.

Any work which is reasonably implied and necessary for satisfactory completionshall be performed by the SUB-CONTRACTOR though not explicitly indicated in

the Specification or shown on the drawings.

Supply as-built drawings.

1.5 Standards and codes of practicePrecast concrete elements should be designed and constructed in compliance with the

Construction Regulations and other relevant codes of practice.

The following specifications, codes and standards, in their last revisions, shall be read inconjunction with and shall be part of this Specification.

1.5.1 Local Construction SpecificationPrecast concrete elementsGood Engineering Practices, BCA-Singapore


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1.5.2 Project Specifications Civil and Structural Design Basis.

Specification for Concrete Works

1.5.3 British StandardsBS EN : 13369 Common rules for precast concrete products

2.0 FABRICATION REQUIREMENTS2.1 Concrete production

For concrete composition, type of cement, use of aggregates, additions and admixtures, and for

resistance to alkali-silica reaction, chloride content and concrete temperature, Projectspecification for concrete shall be referred.

2.2 Placing of concreteConcrete shall be placed as to retain no appreciable amount of entrapped air other thanentrained air and to avoid detrimental segregation. Concrete shall be deposited into forms asnear to its' final location as practical. The free fall of the concrete shall be kept to a minimum.Concrete shall be consolidated in such a manner that segregation of the concrete is minimizedand honeycombed areas are kept to a minimum. Vibrators used to consolidate concrete shallhave frequencies and amplitudes sufficient to produce well consolidated concrete.

2.3 Hot weather concretingDuring hot weather, proper attention shall be given to ingredients, production methods,handling, placing, protection, and curing to prevent excessive concrete temperatures or waterevaporation that could impair required strength or serviceability of the member or structure.

2.4 FormsForms for manufacturing precast concrete products shall be of the type and design consistentwith industry standards. They should be capable of consistently providing uniform products anddimensions. Forms shall be constructed so that no product damage shall be caused by theforces and vibrations to which the forms will be subjected. Forms shall be cleaned of concretebuildup after each use. Coating of form release agents shall not be allowed to build up.

2.5 ReinforcementCages of reinforcement shall be fabricated either by tying the bars, wires or welded wire fabricinto rigid assemblies or by welding where permissible in accordance with Project specifications.Reinforcing shall be positioned as specified by the design and so that the concrete coverconforms to requirements.Positive means shall be taken to assure that the reinforcement does not move significantlyduring the casting operations.


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2.6 Embedded itemsEmbedded items shall be positioned at location specified in the design documents. Inserts,plates, weldments, lifting devices and other items to be imbedded in precast concrete productsshall be held rigidly in place so that they do not move significantly during the castingoperations.

2.7 CuringAll surfaces of newly cast concrete shall be protected against drying out, by at least one of the

methods listed in Table 2 of BS EN 13369, unless it can be shown by tests on the product orotherwise, that no loss in strength or surface cracking will occur in the production environment.

The protection against drying out shall be maintained until the minimum concrete strength(expressed either by the degree of hardening or by the cylinder/cube strength at the end of

curing) given in Table 1 of BS EN 13369is reached. The said tables are reproduced below forready reference.


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2.8 Accelerated hydration by heat treatmentWhere heat treatment at atmospheric pressure is applied to concrete during production in orderto accelerate its hardening, it shall be demonstrated by initial testing that the required strengthis achieved for each concrete family.In order to avoid micro-cracking and/or durability defects, the following conditions shall befulfilled unless previous positive experience has shown that these requirements are notnecessary:

A proper preheating period shall be applied when the heat treatment maximum mean

temperature T exceeds 40 C;

Where T exceeds 40 C the temperature difference between adjacent parts of the elements

during the heating and the cooling phases shall be limited to 20 C.

The preheating period and the heating rate shall be documented.

The concrete strength shall be measured by testing a concrete sample cured in the samemanner as the product. The degree of hardening may be measured either by testing a concretesample or estimated by calculation using a hardening law based on an initial test and maturityconcept.

During the full heating and cooling period the maximum mean temperature T shall be limited tothe values of Table 3 of BS EN 13369. The said table is reproduced below for ready reference.


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3.0 FINISHED PRODUCT REQUIREMENT3.1 Production tolerances

Production tolerances of structural parameters, which affect load-bearing capacity of theelement in its intended use, shall not exceed the values given in Table 4 of BS EN 13369. For

other parameters, different tolerances may be specified.

For cross-sectional dimensionsL, the permitted deviation is L, and for position of reinforcing

steel, prestressing steel and for the design cover c the permitted deviation is c.The said table is reproduced below for ready reference.

3.2 RepairsAny defects found in a precast unit should be checked to ensure that the unit is stillaesthetically and structurally acceptable for use after an appropriate repair is made. The type ofrepair material and method depends on the pattern, extent of the defect and type of surfacefinish and should be agreed by all parties involved and approved by the Engineer. The repairmaterials and method should be effective and acceptable in terms of achieving the required

concrete strength and structural integrity as well as producing a texture and colour similar inappearance to the surrounding surface.

4.0 ERECTION REQUIREMENTS4.1 Erection preparation

Consideration should be given to the following items to ensure safe and efficient installation ofthe precast elements in accordance with the design intent:


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Erection sequence;

Assembly and erection method;Erection tolerances;

Rigging requirements;

Concrete strength or age requirements;

Permanent structural connection and joint details, propping and temporary support details.

4.2 Transient situationsThe following special cases of actions concerning transient situations of precast elements shallbe considered.

Dynamic vertical effects during lifting, handling, transportation and erection shall be considered.

When relevant for the type of element, for transient situations a nominal transverse horizontalforce to cover out of plane effects due to dynamic actions or verticality deviations shall be

considered. This may be taken as 1,5 of the self weight of the element.

4.3 Lifting insertsWhen determining the number and location of lifting inserts, the following should be considered:

a. lifting insert capacity (safe working load);b. total weight of the element;c. strength of concrete at age of liftingd. shape of the unit;e. location of the inserts so that the failure of any one insert does not cause failure of the

entire lifting system thereby ensuring the element can still be safely supported;f. position of any cut-outs and/or openings; andg. rigging arrangement.

All lifting inserts should be purpose designed proprietary products. Reinforcing bars may onlybe used as lifting inserts if specifically designed and installed for this purpose.Typically, lifting inserts should be designed with a factor of safety of 4. Where, they are to beused for multiple lifts such as manhole covers, a factor of safety of 5 should be used. Thesefactors are at ultimate limit state.

4.4 Lifting equipment and accessoriesLifting equipment such as mobile crane, gantry crane, forklift etc. must be carefully selected toensure that lifting of precast units is carried out within the rated capacity of the equipment. Thesupport for the lifting equipment must be checked to ensure that adequate supporting capacityis provided.Lifting accessories may comprise combinations of lifting beams or frames, slings or cables,hooks or shackles. The selection of each of these components should be predetermined to take

account of the forces exerted on them due to all aspects of the lifting operations. A personsuitably qualified in accordance with the relevant regulations must regularly inspect all liftingequipment prior to and after use. Results of such inspections must be properly recorded and beavailable for subsequent inspection by the Engineer upon request.

Some precast elements handled by means of lifting clamps, strops or slings as they may haveno lifting inserts. Lifting equipment of this type may wear rapidly and therefore should beregularly inspected. The location of lifting points should be clearly indicated on the drawings.


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4.5 Joints and connectionsThe overall stability of a structure and the temporary stability of individual members duringconstruction should be checked. If connection failure could result in a catastrophic failure of thestructure, these connections should be avoided.

A free flowing, self-compacting and non-shrink grout should be used at the interface with theprecast elements to minimise the risk of cracking and to ensure good compaction at the joint.

The fire resistance and durability requirements for joints should be at least similar to themembers being connected.

4.6 Sealants for jointsIn choosing the appropriate type of sealant for the joints, consideration should be made inrespect of the movements between the components to be joined, the bond that is achievablebetween the components and the sealant, and the nature of the sealing material itself.

Sealants are classified as elastic, elastoplastic, plastoelastic or plastic according to theirresponse to movement.

High moisture content may be detrimental to the adhesion of the sealant. Sealing should not beundertaken if there is free water present on the surface of the concrete.

4.7 Maintenance of jointsThe design of joints should allow for inspection, repair and, if necessary, replacement ofdeteriorated jointing products during maintenance. All joints should be designed in a mannerthat should be accessible for inspection and repair.

4.8 Erection safetySafety during the handling and erection of precast concrete elements is of paramount

importance and compliance with the relevant regulation is required. All equipment used for thehandling and erection of a precast element must be maintained to a high standard, load testedas necessary, and be suited to the intended use.

Consideration should also be given to the site environment particularly with regards to built upareas and implications this may have on erection safety.

5.0 FACTORY AND SITE STORAGEStorage areas must be large enough so that the precast units can be stored safely, withadequate room for lifting equipment and transporting vehicles to manoeuvre. The ground of thestorage area must be hard, level, clean and well drained to permit organised storage.Precast elements can be damaged by incorrect stacking and storage. Where the locations of

support points for a precast unit are critical the locations for the supports should be noted onthe shop drawings.

Supports must be arranged to avoid twisting or distorting of the precast elements and must beadequate to transfer the weight of the stacked units to the ground without excessive settlement.The stored and stacked units should be protected to prevent accidental damage. Lifting pointsshould also be well protected and kept accessible while the units are in storage.

Precast units must be stored safely with adequate supports such that it would not endanger anyworkers moving in the vicinity.


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6.0 MARKING OF ELEMENTS6.1 Marking Procedure

All elements shall be marked in accordance with following marking procedure.Erection marks

shall include:

Prefix number

Structure number

Level number

Piece number

6.2 Shop MarkingErection marks of all pieces shall be shown on erection drawings and shop drawings.

All shop assembled pieces shall be provided with both:

Cold notched match marks (letters and numbers height 5mm minimum) surrounded

with paint

Painted marks (letters and numbers height 50mm minimum)

The location of the mark shall be on the left hand end of the piece, as detailed. On the

erection diagram the mark shall be in the corresponding "in place" position.

6.3 Packing ListsPacking lists reflecting what is actually shipped shall be furnished with each load in a waterproof package.

7.0 TRANSPORTATIONThe precast units should have gained sufficient strength before being loaded for transportation.

Precast units must be loaded carefully on to delivery vehicles to prevent damage. To protect theedges throughout their journey, proper devices should be used to support, secure and wedgethe precast units. The units should be adequately secured and supported to prevent them from

overturning, shifting or being damaged during transportation. Adequate non-staining cushioningshould be provided between the unit and any securing chains, cables or ropes to preventlocalised damage.

Precautions should also be taken to ensure that no undesirable stresses will be transmitted tothe precast unit due to any flexing of truck or barge deck.


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8.0 QUALITY CONTROL8.1 Shop Quality Control

A factory selected for the casting of units must ensure that the precast units are manufactured

under a Quality Assurance Scheme certified under ISO 9000 covering the following items:

Quality control tests of materials;

Calibration of laboratory equipment for quality control tests.

Production process and control of equipment at the casting yard.

The authorised engineer must satisfy himself that the precast concrete units have beenconstructed in accordance with the Approved Drawings and specification.

Upon leaving the precasting factory all precast units or batch of units must carry documentationcertified by the factory stating that the units have been manufactured under a certified quality

assurance scheme and in accordance with the specification.

8.2 Erection Quality ControlCONTRACTOR shall establish a field inspection system to perform inspections and to

assure conformance to CONTRACT requirements.

Precast Concrete Spec

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