03 11 00 Concrete Forming.pdf

03 11 00 – Concrete Forming

1.0 General

1.1 Section Includes

A. Formwork for cast in place concrete, with shoring, bracing and anchorage.

B. Openings for other Work.

C. Form accessories.

D. Form stripping.

1.2 Design Requirements

A. The Contractor, or their assigns, shall design, engineer and construct formwork, shoring and bracing to conform to code requirements; resultant concrete to conform to required shape, line and dimension.

1.3 Quality Assurance

A. Perform Work in accordance with ACI 117, 301, 318, 347 and 350.

1.4 Regulatory Requirements

A. Conform to applicable codes for design, fabrication, erection and removal of formwork.

1.5 Coordination

A. The Contractor shall coordinate this Section with other sections of Work which require attachment of components to formwork, and with all other prime contracts and/or subcontractors requiring embedment or attachment to formwork.

B. If formwork is placed after reinforcement resulting in insufficient concrete cover over reinforcement, before proceeding the Contractor shall request written instructions from Engineer.

2.0 Products

2.1 Wood Form Materials

A. Plywood for Finish Concrete Exposed to View:

1. Conform to U.S. Product Standard PS-1, B-B Plywood for Concrete Forms, Class I, exterior grade, sound undamaged sheets with clean, true edges. Each piece shall bear legible inspection mark.

2. Use largest practicable sizes to minimize number of joints.

3. Provide form material with sufficient thickness to withstand pressure of newly placed concrete without bow or deflection.

B. Plywood for Finish Concrete Not Exposed to View: Conform to U.S. Product Standard

PS-1, C plugged, exterior grade, sound sheets.

C. Lumber: Sound members of sufficient size and strength to support intended weight, straight edges for tight fit.

2.2 Prefabricated Forms

A. Preformed Steel Forms: Minimum 16 gage matched, tight fitting, stiffened to support weight of concrete without deflection detrimental to tolerances and appearance of finished surfaces.

B. Glass Fiber Fabric Reinforced Plastic Forms: Matched, tight fitting, stiffened to support weight of concrete without deflection detrimental to tolerances and appearance of finished concrete surfaces.

C. Tubular Column Type:

1. Round, spirally wound laminated fiber material, surface treated with release agent, non-reusable.

2. Provide units with sufficient wall thickness to resist loads imposed by wet concrete without deformation.

2.3 Formwork Accessories

A. Form Ties: Removable or snap-off type, adjustable length, cone type, with waterproofing washer, free of defects that could leave holes larger than 1 1/4 inch in concrete surface.

B. Form Release Agent: Colorless mineral oil which will not stain concrete, absorb moisture, or impair natural bonding or color characteristics of coating intended for use on concrete.

C. Corners: Chamfer, rigid plastic or wood strip type; 1 x 1 inch size; maximum possible lengths.

D. Nails, Spikes, Lag Bolts, Through Bolts, Anchorages: Sized as required, of sufficient strength and character to maintain formwork in place while placing concrete.

E. Waterstops: Polyvinyl chloride, minimum 1,750 psi tensile strength, minimum 50 degrees F to plus 175 degrees F working temperature range, 6 inch wide, 3/8-inch thick, maximum possible lengths, ribbed profile, preformed corner sections, heat welded jointing.

3.0 Execution

3.1 Examination

A. The Contractor shall be responsible to verify lines, levels and centers before proceeding with formwork. Ensure that dimensions agree with the Contract Drawings.

3.2 Earth Forms

A. Earth forms are not permitted.

3.3 Erection – Formwork

A. The Contractor shall erect formwork, shoring and bracing to achieve design requirements, in accordance with requirements of ACI 301 and ACI 347.

B. The Contractor shall construct forms to produce concrete of sizes, shapes, lines and dimensions shown, and obtain accurate alignment, location, grades, level and plumb

Work in finished structures.

C. The Contractor shall provide for openings, offsets, sinkages, keyways, recesses, moldings, reglets, chamfers, blocking, screeds, bulkheads, anchorages and inserts, and other features required in Work.

D. The Contractor shall use selected materials to obtain required finishes. Solidly butt joints and provide backup at joints to prevent leakage of concrete.

E. The Contractor shall provide form ties so portion remaining within concrete after removal is at least 1-1/2 inches inside concrete and will not leave holes larger than 1 inch diameter in concrete surface.

F. The Contractor shall provide bracing to ensure stability of formwork. Shore or strengthen formwork subject to overstressing by construction loads.

G. The Contractor shall arrange and assemble formwork to permit dismantling and stripping. Do not damage concrete during stripping. Permit removal of remaining principal shores.

H. The Contractor shall align joints and make watertight. Keep form joints to a minimum.

I. The Contractor shall obtain written approval from the Engineer before framing openings in structural members which are not indicated on the Contract Drawings.

J. The Contractor shall provide chamfer strips on all external corners to produce uniform smooth lines and tight edge joints.

3.4 Application – Form Release Agent

A. The Contractor shall apply form release agent on formwork in accordance with manufacturer's recommendations.

B. The Contractor shall apply prior to placement of reinforcing steel, anchoring devices, and embedded items.

C. The Contractor shall not apply form release agent where concrete surfaces will receive special finishes or applied coverings which are affected by agent. Soak inside surfaces of untreated forms with clean water. Keep surfaces coated prior to placement of concrete.

D. If steel forms are used, the Contractor shall use non-staining, rust preventative form oil. Rust-stained steel formwork is not acceptable.

3.5 Inserts, Embedded Parts, and Openings

A. The Contractor shall provide formed openings where required for items to be embedded in passing through concrete work.

B. The Contractor shall locate and set in place items which will be cast directly into concrete.

C. The Contractor shall coordinate with Work of other sections and other prime contracts and subcontractors in forming and placing openings, slots, reglets, recesses, sleeves, bolts, anchors, other inserts, and components of other Work.

D. The Contractor shall install accessories in accordance with manufacturer's instructions, straight, level, and plumb. Ensure items are not disturbed during concrete placement.

E. The Contractor shall install continuous waterstops without displacing reinforcement.

Seal joints watertight.

F. The Contractor shall provide temporary ports or openings in formwork where required to facilitate cleaning and inspection. Locate openings at bottom of forms to allow flushing water to drain.

G. The Contractor shall close temporary openings with tight fitting panels, flush with inside face of forms, and neatly fitted so joints will not be apparent in exposed concrete surfaces.

3.6 Form Cleaning

A. The Contractor shall clean forms as erection proceeds, to remove foreign matter within forms.

B. The Contractor shall clean formed cavities of debris prior to placing concrete.

C. The Contractor shall flush with water or use compressed air to remove remaining foreign matter. Ensure that water and debris drain to exterior through clean-out ports.

D. The Contractor shall during cold weather, remove ice and snow from within forms. Do not use deicing salts. Do not use water to clean out forms, unless formwork and concrete construction proceed within heated enclosure. Use compressed air or other means to remove foreign matter.

3.7 Formwork Tolerances

A. The Contractor shall construct formwork to maintain tolerances required by ACI 301.

3.8 Field Quality Control

A. The Contractor shall inspect erected formwork, shoring, and bracing to ensure that

Work is in accordance with formwork design, and that supports, fastenings, wedges, ties, and items are secure.

3.9 Form Removal

A. The Contractor shall not remove forms or bracing until concrete has gained sufficient strength to carry its own weight and imposed loads.

B. Formwork not supporting weight of concrete, such as sides of beams, walls, columns, and similar parts of the Work, shall be removed by the Contractor after curing at no less than 50ºF for 12 hours after placing concrete, provided concrete is sufficiently hard to not be damaged by form removal operations, and provided curing and protection operations are maintained.

C. Formwork supporting weight of concrete, such as beam soffits, joints, slabs and other structural elements, shall not be removed in fewer than seven (7) days or until concrete has attained a minimum compressive strength of 2,500 psi, whichever occurs later. The Contractor shall determine potential compressive strength of in place concrete by testing field-cured specimens representative of concrete location or members, to the satisfaction of the Engineer. The costs of testing to verify the minimum compressive strength is achieved shall be borne by Contractor. If no testing is undertaken, forms shall not be removed for 14 days.

D. Form facing material shall be removed by the Contractor four (4) days after placement, only if shores and other vertical supports have been arranged to permit removal of form facing material without loosening or disturbing shores and supports.

E. The Contractor shall loosen forms carefully. Do not wedge pry bars, hammers, or tools against finish concrete surfaces scheduled for exposure to view.

F. The Contractor shall store removed forms in manner that surfaces to be in contact with fresh concrete will not be damaged. Discard damaged forms.

3.10 Form Reuse

A. The Contractor shall clean and repair surfaces of forms to be reused in Work. Split, frayed, delaminated or otherwise damaged form facing material will not be acceptable for exposed surfaces.

B. The Contractor shall apply new form coating compound as specified for new formwork.

C. When forms are extended for successive concrete placement, the Contractor shall thoroughly clean surfaces, remove fins and laitance, and tighten forms to close joints.

Align and secure joint to avoid offsets.

D. The Contractor shall not use "patched" forms for exposed concrete surfaces, except when acceptable to Engineer.

END OF SECTION