CONCRETE FORMWORK

CONCRETE FORMWORK


PART 1 - GENERAL

1.1      THE REQUIREMENT

A. The Contractor shall furnish all materials for concrete formwork, bracing, shoring, and supports and shall design and construct all falsework, in accordance with the provisions of the Contract Documents.

B.    Design Requirements

1. Design concrete forms, falsework, and shoring in accordance with local, state, and federal regulations.

2. Design  forms  and  ties  to  withstand  concrete  pressures  without  bulging, spreading, or lifting of forms.

C.         Performance Requirements

1.         Construct forms so that finished concrete conforms to shapes, lines, grades, and dimensions indicated on the drawings.

2. It is intended that surface of concrete after stripping presents smooth, hard, and dense finish that requires minimum amount of finishing.

3. Provide sufficient number of forms so that the work may be performed rapidly and present uniform appearance in form patterns and finish.

4. Use forms that are clean and free from dirt, debris, concrete, and similar type items. Coat with acceptable form release oil if required, prior to use or reuse.

1.2      REFERENCE SPECIFICATIONS, CODES, AND STANDARDS

A.         Comply with the reference specifications as specified in the General Conditions.
B.         Comply with the current provisions of the following Codes and Standards.
            1.         American Concrete Institute (ACI)
                      a. 117 - Standard Specifications for Tolerances for Concrete Construction and Materials.
                      b.        ACI 347 - Recommended Practice for Concrete Formwork.

1.3      SUBMITTALS

A.         Submittals shall be made in accordance with the General Conditions.
B.         The following submittals and specific information shall be provided:

1. Falsework Calculations and Drawings:  The Contractor's attention is directed to all the latest applicable sections  of the Division of Industrial Safety, Construction Safety Orders, which requires that all falsework or vertical shoring installations where the height of the falsework or vertical shoring, as measured from the top of the sills to the soffit of the superstructure, exceeds 14 feet, or where individual horizontal span lengths exceed 16 feet, or provision for vehicular or railroad traffic through falsework or vertical shoring is made, Plans and Calculations shall be approved and signed by a civil or structural engineer, registered in the State of California; provided further, that a copy of the falsework plan or shoring layout shall be available on the job site at all times.  The engineer who designed the falsework or vertical shoring shall personally inspect such work and provide a written certification that the work conforms to the design.

2. The Contractor shall, in accordance with the requirements in General Conditions submit detailed plans of the falsework proposed to be used.   Such plans and calculations shall be in sufficient detail to indicate the general layout, sizes of members, anticipated stresses, grade of materials to be used in the falsework, and typical soil conditions.

1.4      QUALITY ASSURANCE

A. Tolerances:  The variation from established grade or lines shall not exceed 1/4-inch in 10 feet and there shall be no offsets or visible waviness in the finished surface.  All other tolerances shall be within the "Suggested Tolerances" specified in Section 203 of ACI
347.

B. Qualifications of Formwork Manufacturers:  Use only forming systems manufactured by manufacturers having minimum 5 years experience, except as otherwise specified, or accepted in writing by the Engineer.

C. Regulatory Requirements:  Install work of this Section in accordance with local, state, and federal regulations.

PART 2 - PRODUCTS

2.1      FORM TIES

A.         General

1. Provide  form  ties  for  forming  system  selected  that  are  manufactured  by recognized manufacturer of concrete forming equipment.

2.         Do not use wire ties or wood spreaders of any form.

3.         Provide ties of type that accurately tie, lock, and spread forms.

4. Provide form ties of such design that when forms are removed they locate no metal or other material within 1-1/2 inches of the surface of the concrete.

5. Do  not  allow  holes  in  forms  for  ties  to  allow  leakage  during  placement  of concrete.

B.         Cone-snap or Flat Bar Form Ties

1. Cone-snap ties shall form a cone shaped depression in the concrete with a minimum diameter of 1 inch at the surface of the concrete and 1-1/2 inches deep.

2. Provide neoprene waterseal washer which is located near the center of the concrete.

C.         Taper Ties

1. Neoprene Plugs for Taper Tie Holes: Size so that after they are driven, plugs are located in center third of wall thickeners.

2.         Drypack Mortar for Filling Taper Tie Holes

a.         Consist of mix of 1 part of Portland cement to 1 part of plaster sand.

b. Amount of water to be added to cement-sand mix is to be such that mortar can be driven into holes and be properly compacted.

c.          Admixtures or Additives: Are not to be used in dry-pack mortar.

2.2      BUILT-UP PLYWOOD FORMS

A. Built-up plywood forms may be substituted for prefabricated forming system subject to following minimum requirements:

1.     Size and Material

a. Full size 4 by 8 feet plywood sheets, except where smaller pieces are able to cover entire area.

b.         Sheet Construction: 5-ply plywood sheets, 3/4 inch nominal, made with 100 percent  waterproof  adhesive,  and  having  finish  surface  that  is coated or overlaid with surface which is impervious to water and alkaline calcium and sodium hydroxide of cement.

2.     Wales: Minimum 2 by 4 inch lumber.

3. Studding and Wales:  Contain no loose knots and be free of warps, cups, and bows.

2.3      STEEL OR STEEL FRAMED FORMS

A.         Steel Forms: Provide forms that are:

1. Rigidly constructed and capable of being braced for minimum deflection of finish surface.

2.         Capable of providing finish surfaces that are flat without bows, cups, or dents.

B.         Steel Framed Plywood Forms

1.         Provide forms that are rigidly constructed and capable of being braced.

2.         Plywood  Paneling:  5-ply,  5/8 inch  nominal  or  3/4 inch  nominal,  made  with 100 percent waterproof adhesive, and having finish surface that is coated or overlaid with surface which is impervious to water and alkaline calcium and sodium hydroxide of cement.

2.4      INCIDENTALS

A.         External Angles

1. Where not otherwise indicated on the drawings, provide 3/4 inch bevel, formed by utilizing true dimensioned wood or solid plastic chamfer strip on walkways, slabs, walls, beams, columns, and openings.

2. Provide 1/4 inch bevel formed by utilizing true dimensioned wood or solid plastic chamfer strip on walkways, walls, and slabs at expansion, contraction, and construction joints.

B. Keyways:  Steel, plastic, or lumber treated with form coating, applied according to label directions.

C.     Inserts: Dovetail anchors or ties.

PART 3 - EXECUTION

3.1      GENERAL

A.         Verification of Conditions

1. Do not place any concrete until all forms have been thoroughly checked for alignment, level, strength, and to assure accurate location of all mechanical and electrical inserts or other embedded items.

2. Removal of Formwork: Do not remove forms from concrete which has been placed when outside ambient air temperature is below 50 degrees Fahrenheit until concrete has attained specified strength as determined by test cylinders stored in field under equivalent conditions as concrete structure.

3.2      FORMS AND ACCESSORIES

A.         Vertical Forms

1.         Remain in place minimum of 24 hours after concrete is placed.

2. If, after 24 hours, concrete has sufficient strength and hardness to resist surface or other damage, forms may be removed.

B.         Other Forms Supporting Concrete and Shoring:  Remain in place as follows:

1.         Sides of Footings: 24 hours minimum.

2.         Vertical Sides of Beams, Girders, and Similar Members: 48 hours minimum.

3. Slabs, Beams, and Girders:  Until concrete strength reaches specified strength or until shoring is installed.
4. Shoring for Slabs, Beams, and Girders:  Shore until concrete strength reaches specified strength.

5. Wall Bracing:   Until concrete strength of beams and slabs laterally supporting wall reaches specified strength.

C.         Green Concrete

1.         No heavy loading on green concrete will be permitted.

2. Green concrete is defined as concrete with less than 100 percent of specified strength.

D. Immediately after forms are removed, carefully examine concrete surfaces, and repair any irregularities in surfaces and finishes as specified in Section 03300.

3.3      FORM TIES

A. Cone-snap Rod and Bar Ties:   Tie forms together at not more than 2-foot centers vertically and horizontally. After forms are removed from wall, fill tie holes as follows:

1.         Remove form ties from surfaces.

2.         Roughen cone shaped tie holes by heavy sandblasting before repair.

3.         Dry   pack   cone   shaped   tie   holes   with   drypack   mortar   as   specified   in
Section 03600.

B.         Taper Ties

1. Neoprene Plug in Taper Tie Holes:  After forms and taper ties are removed from wall, plug tie holes with neoprene plug as follows:

a.      Heavy sandblast and then clean tie holes.

b. After cleaning, drive neoprene plug into each of taper tie holes with steel rod. Final location of neoprene plug shall be in center third of wall thickness. Bond neoprene plug to concrete with epoxy.

c.      Locate steel rod in cylindrical recess, made in plug, during driving.

(1) At no time are plugs to be driven on flat area outside cylindrical recess.

C.         Dry Pack of Taper Tie Holes:  After Installing Plugs in Tie Holes

1. Coat tie hole surface with epoxy bonding agent and fill with drypack mortar as specified in Section 03600.

2. Drypack Mortar:  Place in holes in layers with thickness not exceeding tie hole diameter and heavily compact each layer.

3. Dry pack the outside of the hole no sooner than 7 days after the inside of the hole has been dry packed.

4. Wall Surfaces in Area of Drypacked Tie Holes:   On the water side of water containing structures and the outside of below grade walls:

a.         Cover with minimum of 10 mils of epoxy gel.

b.         Provide  epoxy  gel  coating  on  wall  surfaces  that  extend  minimum  of
2 inches past drypack mortar filled tie holes.

c.          Provide finish surfaces that are free from sand streaks or other voids.

3.4 BUILT-UP PLYWOOD FORMS

A. Studding
1.         Concrete work.

2.         Spaced at 16 inches or 24 inches on center.

3. Closer spacing may be required depending upon strength requirements of the forms.   In order to prevent any bulging surfaces install studs perpendicular to grain of exterior plys of plywood sheets.

B.         Wales: Form wales of double lumber material minimum size as specified in this Section.

C.         Number of Form Reuses:  Depends upon durability of surface coating or overlay used,
and ability to maintain forms in condition such that they are capable of producing flat, smooth, hard, dense finish on concrete when stripped.

3.5      STEEL OR STEEL FRAMED FORMS

A.         Steel Forms: Adequately brace forms for minimum deflection of finish surface.

B.         Steel Framed Plywood Forms
1.         Rigidly construct and brace with joints fitting closely and smoothly.

2. Number of Form Reuses:  Depends upon durability of surface coating or overlay used.

C. Built-up plywood forms as specified in this Section may be used in conjunction with steel forms or steel framed plywood forms for special forming conditions such as corbels and forming around items which will project through forms.

3.6      FORM WORK FOR ARCHITECTURAL FLUTING

A.         Provide high quality thick gauge form materials which will not degrade when reused.

3.7      BRACING AND ALIGNMENT OF FORMS

A. Line and Grade:   Limit deviations to tolerances which will permit proper installation of structural embedded items or mechanical and electrical equipment and piping.

B.         Formwork

1. Securely brace, support, tie down, or otherwise hold in place to prevent any movement.

2. Make adequate provisions for uplift pressure, lateral pressure on forms, and deflection of forms.

C. When Second Lift is Placed on Hardened Concrete:  Take special precautions in form work at top of old lift and bottom of new lift to prevent:

1.         Spreading and vertical or horizontal displacement of forms.

2.         Grout "bleeding" on finish concrete surfaces.

D.         Pipe Stubs, Anchor Bolts, and Other Embedded Items:  Set in forms where required.

E. Cracks, Openings, or Offsets at Joints in Formwork:  Close those that are 1/16 inch or larger by tightening forms or by filling with acceptable crack filler.

3.8      INCIDENTALS

A.         Keyways: Construct keyways as indicated on the drawings.

B.         Exterior Corners: Provide 3/4-inch chamfer unless otherwise specified.

C.         Reentrant Angles: May be left square.

D. Level Strips:  Install level strips at top of wall concrete placements to maintain true line at horizontal construction joints.

E.         Inserts

1. Encase  pipes,  anchor  bolts,  steps,  reglets,  castings,  and  other  inserts,  as indicated on the drawings or as required, in concrete.

2. Use  dovetail  anchors  or  ties  in  conjunction  with  slots  or  inserts  for  various materials as specified under other sections of these Specifications and as may be necessary for required work.

3.9      PIPE AND CONDUIT

A. Install  pipe  and  conduit  in  structures  as  indicated  on  the  drawings,  and  seal  with materials as specified in Section 07900.

3.10    TOLERANCES

A. Finish concrete shall conform to shapes, lines, grades, and dimensions indicated on the drawings.

B. The maximum deviation from true line and grade shall not exceed tolerances listed below at time of acceptance of project.

C.         General:  Comply with ACI 117, Paragraphs 2.0 through 2.2 and Paragraphs 4.0 through
4.5, except as modified in following:

1.         Slabs

a. Slope:    Uniformly  sloped  to  drain  when  slope  is  indicated  on  the drawings.

b.         Slabs Indicated to be Level:   Have maximum deviation of 1/8 inch in
10 feet without any apparent changes in grade.

2. On Circular Tank Walls:  The Contractor may deviate from finish line indicated on the drawings by use of forms with chord lengths not to exceed 2 feet.

3. Inserts: Set inserts to tolerances required for proper installation and operation of equipment or systems to which insert pertains.

4.         Maximum Tolerances: As follows:
Item Inches  
Sleeves and Inserts Plus 1/8 Minus 1/8  
Projected Ends of Anchor Bolts Plus 1/4 Minus 0.0  
Anchor Bolt Setting Plus 1/16 Minus 1/16

END OF SECTION