03 45 00 Pre-Cast Architectural Concrete.docx

01-01-21

SECTION 03 45 00

PRECAST ARCHITECTURAL CONCRETE

GENERAL

DESCRIPTION

This section includes the performance criteria, materials, production, and erection of architectural precast concrete cladding units. The work performed under this section includes all labor, material, equipment, related services, and supervision required for the manufacture and erection of the architectural precast concrete work shown on the construction documents.

RELATED WORK

Section 01 45 29, TESTING LABORATORY SERVICES: Materials testing and inspection during construction.

Section 03 30 00, CAST-IN-PLACE CONCRETE: Concrete.

Section 04 05 13, MASONRY MORTARING: Mortar.

Section 04 05 16, MASONRY GROUTING: Grout.

Section 04 20 00, UNIT MASONRY: Masonry Facing.

Section 04 72 00, CAST STONE MASONRY: Cast Stone Facing.

Section 07 92 00, JOINT SEALANTS: Sealants and Caulking.

QUALITY ASSURANCE

Fabricator Qualifications: A firm that complies with PCI MNL 117 and the following requirements and is experienced in producing units similar to those indicated for this Project and with a record of successful in‑service performance:

Participates in PCI’s Plant Certification program at the time of bidding and is designated a PCI-certified plant for Group A, Category A1- Architectural Cladding and Load Bearing Units. Submit PCI certification.

Fabricator must have a minimum of three (3) years’ experience in Precast Architectural Concrete work comparable to that shown and specified in not less than three (3) projects of similar scope with the Government determining the suitability of experience.

Testing Laboratory Accreditation Requirements: Construction materials testing laboratories must be accredited by a laboratory accreditation authority. Submit a copy of the Certificate of Accreditation and Scope of Accreditation.

Quality-Control Standard: For manufacturing procedures and testing requirements, quality-control recommendations, and dimensional tolerances for types of units required, comply with PCI MNL 117.

Sample Panels: Before fabricating units, produce a minimum of two (2) sample panels approximately 1.5 sq. m. (16 sq. feet) in size for review by the Contracting Officer Representative (COR). Incorporate full scale details of architectural features, finishes, textures, and transitions in the sample panels. Approved sample panel will be used for mockup and range sample.

Locate panels where indicated or, if not indicated, as directed by COR.

Damage part of an exposed-face surface for each finish, color, and texture, and demonstrate adequacy of repair techniques proposed for repair of surface blemishes.

After acceptance of repair technique by COR, maintain one (1) sample panel at the manufacturer’s plant and one (1) at the project site in an undisturbed condition as a standard for judging the completed work.

When back face of precast concrete unit is to be exposed, show samples of the workmanship, color, and texture of the backup concrete as well as the facing.

Demolish and remove sample panels only when directed by COR.

Range Samples: After sample panel approval and before production of units for installation, produce a minimum of three (3) samples, approximately 1.5 sq. feet in size, representing anticipated range of color and texture of project. Following range sample acceptance by the COR, maintain samples at the manufacturer’s plant and the Project site as color and texture acceptability reference.

Mockups: After sample panel and range sample approval but before production of units, construct full sized mockups to verify selections and to demonstrate aesthetic effects and qualities of materials and execution. Mockup to be representative of the finished work in all respects including glass, aluminum framing, sealants and architectural precast concrete complete with all anchors, connections, flashings, and joint fillers as approved on the final shop drawings. Build mockups to comply with the following requirements, using materials indicated for the completed work:

Build mockups in the location and of the size indicated or, if not indicated, as directed by COR.

Notify COR in advance of dates and times when mockups will be constructed.

Obtain COR’s approval of mockups before starting fabrication.

Maintain mockups during construction in an undisturbed condition as a standard for judging the completed Work.

Demolish and remove mockups when directed by COR.

Preinstallation Conference: Conduct conference at Project site to comply with requirements in Division 01, GENERAL REQUIREMENTS.

PERFORMANCE REQUIREMENTS

Structural Performance: Provide units and connections capable of withstanding: the design criteria specified on the construction documents, self-weights and weights of materials supported or attached, for the conditions indicated.

Design Standards: Comply with ACI 318/ACI 318M and the design recommendations of PCI MNL 120 and PCI MNL 122 applicable to types of units indicated.

Limit deflection of precast members as follows:

Vertical live load – Span / 360.

Wind load – Height / 400.

Thermal Movements: Provide for in-plane thermal movements resulting from annual ambient temperature changes of 49 degrees C (120 degrees F).

SOURCE QUALITY CONTROL

Quality-Control Testing: Test and inspect precast concrete according to Section 01 45 29, TESTING LABORATORY SERVICES and PCI MNL 117 requirements respectively. If using self-consolidating concrete also test and inspect according to PCI TR-6.

Testing: When determined by the COR that there is evidence that the concrete strength of precast concrete units may be deficient, employ an independent testing agency at Contractor’s expense to obtain, prepare, and test cores drilled from hardened concrete to determine compressive strength according to PCI MNL 117:

Submit test results in writing on the same day that tests are performed, with copies to COR, Contractor, and precast concrete fabricator. Include the information required in Section 01 45 29, TESTING LABORATORY SERVICES and the following:

Identification mark and type of precast concrete units represented by core tests; design compressive strength; type of break; compressive strength at breaks, corrected for length-diameter ratio; and direction of applied load to core in relation to horizontal plane of concrete as placed.

Defective or Damaged Work: Units that do not comply with acceptability requirements, including concrete strength, manufacturing tolerances, and color and texture range are unacceptable. Chipped, spalled or cored units may be repaired, if repaired units match the visual mock-up. The COR will reject units that do not match the accepted samples and visual mock-up. Remove unacceptable units from the site and replace with precast concrete units that comply with requirements.

SUBMITTALS

Product Data: For each type of product indicated.

Design Mixes: For each concrete mix along with compressive strength and water-absorption tests.

Shop (Erection) Drawings: Detail fabrication and installation of units.

Indicate member locations with distinctive marks that match marks placed on the panels. Provide plans, elevations, dimensions, corner details, shapes, cross sections and relationships to adjacent materials.

Indicate aesthetic characteristics including joints, reveals, and extent and location of each surface finish.

Indicate separate face and backup mix locations, and thicknesses. Indicate locations, extent and treatment of dry joints if two-stage casting is proposed.

Indicate welded connections by AWS standard symbols. Detail loose and cast-in hardware, and connections.

Indicate locations, tolerances and details of anchorage devices to be embedded in or attached to structure or other construction.

Samples: Design reference samples for initial verification of design intent, approximately 305 by 305 by 50 mm (12 by 12 by 2 inches), representative of finishes, color, and textures of exposed surfaces of units.

Samples for each facing unit required, showing the full range of color and texture expected. Supply sketch of each corner or special shape with dimensions. Supply sample showing color and texture of joint treatment.

Testing laboratory accreditations.

Material Test Reports: From an accredited testing agency indicating and interpreting test results of the following for compliance with requirements indicated:

Concrete strengths and mix designs.

Material Certificates: Signed by manufacturers certifying that each of the following items complies with requirements.

Cementitious materials.

Reinforcing materials and prestressing tendons.

Admixtures.

Facing units.

Anchors.

PRODUCT DELIVERY, STORAGE AND HANDLING

Comply with product handling requirements of PCI MNL 117 at the plant and project site.

Deliver all units to the project site in such quantities and at such times to assure compliance with the agreed project schedule and proper setting sequence so as to limit unloading units temporarily on the ground.

Lift and support units only at designated points shown on the shop drawings.

Furnish loose connection hardware and anchorage items to be embedded in or attached to other construction without delaying the Work. Provide setting diagrams, templates, instructions, and directions, as required, for installation.

Store units with adequate dunnage and bracing, and protect units to prevent contact with soil to prevent staining, and to prevent cracking, distortion, warping, and other physical damage. Place stored units so identification marks are clearly visible for inspection.

WARRANTY

Construction Warranty: Comply with FAR clause 52.246-21 “Warranty of Construction”.

APPLICABLE PUBLICATIONS

Publications listed below form a part of specification to extent referenced. Publications are referenced in text by basic designation only.

ASTM International (ASTM):

American Concrete Institute (ACI):

Military Specifications (MIL. Spec):

MIL-C882E-89 Cloth, Duck, Cotton or Cotton-Polyester Blend Synthetic Rubber, Impregnated, and Laminated, Oil Resistant

PRODUCTS

MOLD MATERIALS

Molds: Rigid, dimensionally stable, nonabsorptive material, warp and buckle free, that will provide continuous and true precast concrete surfaces within fabrication tolerances indicated; non-reactive with concrete and suitable for producing required finishes:

Mold-Release Agent: Commercially produced form-release agent that will not bond with, stain or adversely affect precast concrete surfaces and will not impair subsequent surface or joint treatments of precast concrete.

Form Liners: Units of face design, texture, arrangement, and configuration indicated. Provide solid backing and form supports to ensure that form liners remain in place during concrete placement. Use with manufacturer’s recommended liquid-release agent that will not bond with, stain, or adversely affect precast concrete surfaces and will not impair subsequent surface or joint treatments of precast concrete.

REINFORCING MATERIALS

Reinforcing Steel: ASTM A615/A615M, Grade 60 (Grade 420), deformed.

Weldable Reinforcing Bars: ASTM A706/A706M, deformed.

Galvanized Reinforcing Bars: ASTM A767/A767M, Class II zinc coated, hot-dip galvanized and chromate wash treated after fabrication and bending.

Deformed-Steel Welded Wire Reinforcement: ASTM A1064/A1064M, flat sheet.

Supports: Suspend reinforcement from back of mold or use bolsters, chairs, spacers, and other devices for spacing, supporting, and fastening reinforcing bars and welded wire reinforcement in place according to PCI MNL 117.

CONCRETE MATERIALS

Portland Cement: ASTM C150/C150M, Type I or III.

For surfaces exposed to view in finished structure, use gray, same type, brand, and mill source throughout the precast concrete production.

Standard gray Portland cement may be used for non-exposed backup concrete.

Supplementary Cementitious Materials for unexposed surfaces (backup concrete) only.

Fly Ash Admixture: ASTM C618, Class C or F with maximum loss on ignition of 3 percent.

Metakaolin Admixture: ASTM C618, Class N.

Silica Fume Admixture: ASTM C1240 with optional chemical and physical requirement.

Ground Granulated Blast-Furnace Slag: ASTM C989/C989M, Grade 100 or 120.

Normal-Weight Aggregates: Except as modified by PCI MNL 117, ASTM C33/C33M, with coarse aggregates complying with Class 5S. Provide and stockpile fine and coarse aggregates for each type of exposed finish from a single source (pit or quarry) for entire project.

Face-Mix Coarse Aggregates: Selected, hard, and durable; free of material that reacts with cement or causes staining; to match selected finish sample.

Gradation: Uniformly graded to match design reference sample.

Hard durable quartz, marble, granite, siliceous stone aggregate carefully graded from coarse to fine in proportions required to match approved samples.

Eliminate off color material from exposed aggregate.

Face-Mix Fine Aggregates: Selected, natural or manufactured sand of the same material as coarse aggregate, unless otherwise approved by COR.

Test sand for color value in accordance with ASTM C40/C40M. Sand producing darker than specified color standard is unacceptable.

Clean washed white sand.

Admixtures: Admixtures containing calcium chloride, or more than 0.15 percent chloride ions or other salts by weight of admixture are not permitted.

Coloring Admixture: ASTM C979/C979M, synthetic or natural mineral-oxide pigments or colored water-reducing admixtures, temperature stable and non-fading.

Air Entraining Admixture: ASTM C260, certified by manufacturer to be compatible with other required admixtures.

Water-Reducing Admixture: ASTM C494/C494M, Type A.

Retarding Admixture: ASTM C494/C494M, Type B.

Water-Reducing and Retarding Admixture: ASTM C494/C494M, Type D.

High-Range, Water-Reducing Admixture: ASTM C494/C494M, Type F.

High-Range, Water-Reducing and Retarding Admixture: ASTM C494/C494M, Type G.

Plasticizing Admixture for Flowable Concrete: ASTM C1017/C1017M.

Water: Potable; free from deleterious material that may affect color stability, setting, or strength of concrete and complying with chemical limits of PCI MNL 117.

GROUT MATERIALS

Sand-Cement Grout: Portland Cement, ASTM C150/C150M, Type I, and clean, natural sand, ASTM C144, or ASTM C404. Mix at ratio of 1 part cement to 2‑1/2 parts sand, by volume, with minimum water required for placement and hydration.

Nonmetallic, Nonshrink Grout: Premixed, nonmetallic, noncorrosive, nonstaining grout containing selected silica sands, portland cement, shrinkage-compensating agents, plasticizing and water-reducing agents, complying with ASTM C1107/C1107M, Grade A for drypack and Grades B and C for flowable grout and of a consistency suitable for application within a 30-minute working time.

Epoxy-resin grout: Two-component mineral-filled epoxy-resin: ASTM C881 of type, grade, and class to suit requirements.

CONCRETE MIXES

Prepare design mixes to match COR’s sample for each type of concrete required.

Limit use of fly ash and granulated blast-furnace slag to 20 percent replacement of Portland cement by weight; metakaolin and silica fume to 10 percent of Portland cement by weight.

Provide design mixes prepared by a qualified independent testing agency or by qualified precast plant personnel at fabricator’s option.

Limit water-soluble chloride ions to the maximum percentage by weight of cement permitted by ACI 318/318M or PCI MNL 117 when tested in accordance with ASTM C1218/C1218M.

Normal Weight Concrete Face and Backup Mixtures: Proportion mixes by either laboratory trial batch or field test data methods according to ACI 211.1, with materials to be used on Project, to provide normal-weight concrete with the following properties:

Compressive Strength (28 Days): 34.5 MPa (5000 psi).

Maximum Water-Cementitious Materials Ratio: 0.45.

Release strength as required by design.

Lightweight Concrete Back-Up Mixes: Proportion mixes by either laboratory trial batch or field test data methods according to ACI 211.2, with materials to be used on Project, to provide lightweight concrete with the following properties:

Compressive Strength (28 Days): 34.5 MPa (5000 psi).

Unit Weight: Calculated equilibrium unit weight of 1842 kg per cubic meter (115 lb. per cubic feet), plus or minus 48 kg per cubic m (3 lb. per cubic feet), according to ASTM C567/C567M.

Water Absorption: 6 percent by weight or 14 percent by volume, tested according to PCI MNL 117.

Add air-entraining admixture at manufacturer’s prescribed rate to result in concrete at point of placement having air content as follows.

Total air content for various sizes of coarse aggregate for normal weight concrete.

Nominal Maximum Size of Aggregate mm (inch)

When included in design mixes, add other admixtures to concrete mixes according to manufacturer’s written instructions.

EXECUTION

MOLD FABRICATION

Molds: Construct and maintain molds, mortar tight, within fabrication tolerances and of sufficient strength to withstand pressures due to concrete-placement, vibration operations, and temperature changes and for prestressing and detensioning operations.

Form joints are not acceptable on faces exposed to view in the finished work.

Edge and Corner Treatment: Uniformly radiused.

FABRICATION

Cast-in Anchors, Inserts, Plates, Angles, and Other Anchorage Hardware: Fabricate anchorage hardware with sufficient anchorage and embedment to comply with design requirements. Position anchors for attachment of loose hardware and secure in place during precasting operations. Locate anchorage hardware where it does not affect position of main reinforcement or concrete placement.

Weld headed studs and deformed bar anchors used for anchorage according to AWS D1.1/D1.1M and AWS C5.4.

Furnish loose hardware items including steel plates, clip angles, seat angles, anchors, dowels, cramps, hangers, and other hardware shapes for securing units to supporting and adjacent construction.

Provide cast-in reglets, slots, holes, and other accessories in units as indicated on contract documents.

Provide cast-in openings larger than 254 mm (10 inches) in any dimension. Do not drill or cut openings or reinforcing without approval of COR.

Reinforcement: Comply with recommendations in PCI MNL 117 for fabrication, placing, and supporting reinforcement.

Place reinforcing steel and prestressing strand to maintain at least 19 mm (3/4 inch) minimum concrete cover. Increase cover requirements for reinforcing steel to 38 mm (1-1/2 inches) when units are exposed to corrosive environment or severe exposure conditions. Arrange, space, and securely tie bars and bar supports to hold reinforcement in position while placing concrete.

Install welded wire reinforcement in lengths as long as practicable. Lap adjoining pieces at least one (1) full mesh spacing and wire tie laps, where required by design. Offset laps of adjoining widths to prevent continuous laps in either direction.

Clean reinforcement of loose rust and mill scale, earth, and other materials that reduce or destroy the bond with concrete. When damage to epoxy-coated reinforcing exceeds limits specified in ASTM A775/A775M, repair with patching material compatible with coating material and epoxy coat bar ends after cutting.

Accurately position, support, and secure reinforcement against displacement during concrete- placement and consolidation operations. Completely conceal support devices to prevent exposure on finished surfaces.

Mix concrete according to PCI MNL 117 and requirements in PART 2. After concrete batching, no additional water may be added.

At the fabricator’s option either of the following mix design/casting techniques may be used:

A single design mix throughout the entire thickness of panel.

Design mixes for facing and backup; using cement and aggregates for each type as indicated, for consecutive placement in the mold. Use cement and aggregate specified for facing mix, use cement and aggregate for backup mix complying with criteria specified as selected by the fabricator.

Place concrete in a continuous operation. Comply with requirements in PCI MNL 117.

Place self-consolidating concrete without vibration in accordance with PCI TR-6.

Cure concrete, according to requirements in PCI MNL 117, by moisture retention without heat accelerated heat curing using low-pressure live steam radiant heat and moisture.

Repair damaged units to meet acceptability requirements of PCI MNL 117 and the COR.

Reinforce architectural precast concrete units to resist handling, transportation and erection stresses, and specified in-place loads, whichever governs.

Comply with requirements in PCI MNL 117 and requirements in this section for measuring, mixing, transporting, and placing concrete. After concrete batching, no additional water may be added.

Place face mixture to a minimum thickness after consolidation of the greater of 25 mm (1 inch) or 1.5 times the nominal maximum aggregate size, but not less than the minimum reinforcing cover of 38 mm (1-1/2 inches).

Use a single design mixture for those units in which more than one major face (edge) is exposed.

Where only one (1) face of unit is exposed, at the fabricator’s option, either of the following mixture design/casting techniques may be used:

A single design mix throughout the entire thickness of panel.

Separate mixtures for face and backup concrete; using cement and aggregates for each type as appropriate, for consecutive placement in the mold. Use cement and aggregate specified for face mixture. Use cement and aggregate for backup mixture complying with specified criteria or as selected by the fabricator.

Thoroughly consolidate placed concrete by internal or external vibration without dislocating or damaging reinforcement and built-in items, and minimize pour lines, honeycombing, or entrapped air voids on surfaces. Use equipment and procedures complying with PCI MNL 117.

Place self-consolidating concrete without vibration in accordance with PCI TR-6.

Comply with PCI MNL 117 procedures for hot- and cold-weather concrete placement.

FABRICATION TOLERANCES

Fabricate units straight and true to size and shape with exposed edges and corners precise and true so each finished unit complies with PCI MNL 117 product tolerances as well as position tolerances for cast-in items.

Fabricate architectural trim units such as sills, lintels, coping, cornices, quoins, medallions, with tolerances meeting PCI MNL 135.

FINISHES

Provide exposed panel faces free of joint marks, grain, and other obvious defects. Corners, including false joints to be uniform, straight and sharp. Finish exposed-face surfaces of units to match approved design reference sample, sample panels, mockups and as follows:

PCI’s “Architectural Precast Concrete –Color and Texture Selection Guide,” of plate numbers indicated.

As-Cast Surface Finish: Provide surfaces free of excessive air voids, sand streaks, and honeycombs.

Finish exposed top, bottom, and back surfaces of units to match face-surface finish.

Finish unexposed surfaces top, bottom, and back of units by smooth steel-trowel finish.

Finish unexposed surfaces of units by float finish.

ERECTION PREPARATION

Deliver anchorage devices that are embedded in or attached to the building structural frame or foundation before start of such work. Furnish locations, setting diagrams, and templates for the proper installation of each anchorage device.

Examine supporting structural frame or foundation and conditions for compliance with requirements for installation tolerances, true and level bearing surfaces, and other conditions affecting performance. Proceed with installation only after unsatisfactory conditions have been corrected.

Do not install units until supporting cast-in-place concrete building structural framing has attained minimum allowable design strength and is structurally ready to receive loads from precast.

ERECTION

Erect units level, plumb and square within the specified allowable tolerances. Provide temporary supports and bracing as required to maintain position, stability, and alignment of units until permanent connections are completed.

Install temporary steel or plastic spacing shims or bearing pads as precast concrete units are being erected. Tack weld steel shims to each other to prevent shims from separating.

Maintain horizontal and vertical joint alignment and uniform joint width as erection progresses.

Remove projecting lifting devices and use sand-cement grout to fill voids within recessed lifting devices flush with surface of adjacent precast concrete surfaces when recess is exposed.

Unless otherwise shown provide for uniform joint widths of 9.5 mm (3/8 inch).

Connect units in position by bolting, welding, grouting, or as otherwise indicated on approved Erection Drawings. Remove temporary shims, wedges, and spacers as soon as practical after connecting or grouting are completed.

Grouting Connections: Grout connections where required or indicated on shop (erection drawings). Retain flowable grout in place until strong enough to support itself. Pack spaces with stiff grout material, tamping until voids are completely filled. Place grout and finish smooth, level, and plumb with adjacent concrete surfaces. Promptly remove grout material from exposed surfaces before it affects finishes or hardens.

Venting and Weeps: Where precast concrete panels form the outer wythe of cavity wall construction, vent the cavity wall.

Use polyvinyl chloride plastic tubing to vent the cavity.

Place plastic vent tubes "tilted down and out" in horizontal and vertical joints.

Space vent tubes in accordance with shop drawings, but not less than two vents per panel or approximately 1219 mm (4 feet) on centers.

Setting: Where shown, fill joints with cement mortar specified in Section 04 05 13, MASONRY MORTARING Section 04 05 16, MASONRY GROUTING.

Clean surfaces forming beds and other joints for precast concrete panels of dust, dirt, and other foreign matter, and wet thoroughly to prevent suction before precast concrete, elements are set.

Set precast element level and true to line with uniform joints filled completely with mortar.

Joints required to have only sealant to be kept free of mortar for full depth.

Keep exposed faces of precast concrete elements free of mortar.

Remove wedges, spacers, or other appliances which are likely to cause staining from joints.

Where parging is shown, parge back of elements solid with mortar. Apply paging without skips or holidays.

Pointing: Wash and brush clean, leaving joints free from loose mortar, dust and other foreign material.

Carefully point with a slightly concave joint.

Mortar for pointing as specified in Section 04 05 13, MASONRY MORTARING Section 04 05 16, MASONRY GROUTING. Provide same material and color sand used in fabrication of precast concrete elements.

Sealing of Joints: Where shown and where required to make work watertight: clean, dry and seal joints between precast concrete elements and between precast elements and adjoining materials as specified in Section 07 92 00, JOINT SEALANTS.

CLEANING:

Clean surfaces of precast concrete to be exposed to view, as necessary, prior to shipping.

Clean mortar, plaster, fireproofing, weld slag, and any other deleterious material from concrete surfaces and adjacent materials immediately.

Clean exposed surfaces of precast concrete units after erection and completion of joint treatment to remove weld marks, other markings, dirt, and stains.

Perform cleaning procedures, if necessary, according to precast concrete fabricator’s recommendations. Clean soiled precast concrete surfaces with detergent and water, using stiff fiber brushes and sponges, and rinse with clean water. Protect other work from staining or damage due to cleaning operations.

Do not use cleaning materials or processes that could change the appearance of exposed concrete finishes or damage adjacent materials.

END OF SECTION

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