SECTION 031000 CONCRETE FORMWORK ___________________________________________________________________________ PART 1 - GENERAL
1.1
1.2
DESCRIPTION A.
This section specifies formwork for all Concrete Work indicated as in-situ Concrete on the drawings.
B.
Items included are design and construction of formwork, stability, surface finish achieved, cleaning, cast-in fixings and striking times.
RELATED SECTION Cast-in-Place Concrete – Section 033000
1.3
REFERENCES A.
Formwork shall be constructed to maintain the correct positions, shape, profile and surface finish of the Concrete in accordance with the following standards and this Specifications.
B.
Formwork shall satisfy the requirements recommendations of the following Standards: 1.
b.
3.
Project No. MK-1204
comply
with
the
BS – BRITISH STANDARDS a.
2.
and
BS 8110: Part 1, ISO 3443:
BS 5606:
Code of Practice for the Structural Use of Concrete Code of Practice for accuracy in Building
ACI – AMERICAN CONCRETE INSTITUTE a.
ACI 301:
Specification for Structural Concrete for Buildings
b.
ACI 318:
Building Code Requirements for Reinforce Concrete
c.
ACI 308:
Curing Concrete
d.
ACI 347:
Recommended Practice for Concrete Formwork
APA - AMERICAN PLYWOOD ASSOCIATION: a.
High Density Overlaid Concrete Form, Class 1
b.
Structural 1, Exterior Quality, Class 1
c.
Plastic Overlaid Plywood Forms
Volume II
031000-1
SECTION 031000 CONCRETE FORMWORK ___________________________________________________________________________
4.
ANSI - AMERICAN NATIONAL STANDARD INSTITUTE: a.
1.4
A199.1:
Construction and Industrial Plywood
SUBMITTALS A.
MANUFACTURER’S DATA: Submit manufacturer's specifications and installation instructions for proprietary materials and items as required, including form coatings, manufactured form systems, ties and accessories.
1.5
B.
Submit shop drawing for all formwork showing locations of tie bolts and cones, openings, chamfers, water stops, inserts, fittings and accessories for the approval of the Engineer.
C.
All formwork to be erected using cones and tie bolts for securing the formwork.
D.
Electrical, Mechanical and plumbing reservation, coordination drawings before concreting.
QUALITY ASSURANCE: A.
Design, construct, erect, support, brace, maintain, and remove forms in conformance with the requirements of ACI 318, Parts 1, 2 and 3 inclusive and ACI 347 for loads, lateral pressure, and allowable stresses; in addition to other design parameters such as wind loads. 1.
CONSTRUCTION: Construct formwork so that cast concrete surfaces will comply with ACI 301, Chapter 4, Par. 4.3 Tolerances.
2.
HYDRAULIC PRESSURE: The maximum allowable deflection of forming surfaces from concrete pressure is length/360 between supports.
1.6
3.
Provide surveys as required to check the lines and levels of the completed formwork for exposed concrete before concrete is placed. Make any required corrections or adjustments to formwork to correct deviations which exceed specified tolerances.
4.
Check formwork during concrete placement to ensure forms, shores, falsework, ties and other features have not been unduly disturbed by concrete placement methods or equipment. The Contractor shall report in writing to the Employer's Representative any deviations from the allowable tolerances.
PRODUCT HANDLING
Project No. MK-1204
Volume II
031000-2
SECTION 031000 CONCRETE FORMWORK ___________________________________________________________________________
The formwork shall be so handled and erected that the concrete shall not suffer due to defects or damage to the formwork. PART 2 - PRODUCTS
A.
ORDINARY FORMWORK This shall be obtained by the use of properly designed formwork or moulds of closely jointed sawn boards. The surface shall be free from voids, honeycombing or other large blemishes.
B.
FAIRFACE FORMWORK This finish shall be obtained by the use of properly designed forms of closely jointed type plywood boards where indicated on the drawings. The surface shall be free from voids, honeycombing or blemishes. The surface shall then be improved by carefully removing all fins and other projections.
C.
CHAMFERS and GROOVES The chamfers and grooves shall be obtained by wrought hardwood fillet of size and location indicated on the drawings. All slabs, drop beams and columns in the parking areas shall have chamfers and grooves where shown on the drawings.
D.
FORM TIES The ties for securing forms for ordinary formwork and for fairface plywood works shall be factory fabricated, adjustable length tie screws with removable plastic cones and removable bolts. When forms are removed, no metal shall be closer than 40mm from the concrete surface. For water tanks or other water retained structures, use water tight form ties as recommended by the Manufacturer. Form ties fabricated on project site and wire ties are not acceptable.
E.
FORM COATING Form coating shall be of a type which does not import any stain to concrete nor interface with the adhesive of any finish, sealant, waterproofing material applied to any concrete surface and which has been approved by the Engineer.
PART 3 - EXECUTION
A.
DESIGN and CONSTRUCTION The design and construction of formwork shall be carried out by competent persons employed by the Contractor, taking due account of the surface finish required.
Project No. MK-1204
Volume II
031000-3
SECTION 031000 CONCRETE FORMWORK ___________________________________________________________________________
The formwork shall be sufficiently rigid and tight to prevent loss of grout or mortar from the concrete at all stages and for the appropriate method of placing and compacting. Formwork (including supports) shall be sufficiently rigid to maintain the forms in their correct position, shape and profile within the limits of the dimensional tolerances specified in Table 293 of BS 5606 or ACI 301 The supports shall be designed to withstand the worst combination of self-weight, formwork weight, formwork forces, reinforcement weight, wet concrete weight, construction and wind loads, together with all incidental dynamic effects caused by placing, vibrating and compacting the concrete. The Contractor shall make allowance for any settlement or deflection of formwork that is likely to arise during construction, so that the hardened concrete conforms accurately to the specified line and level. The formwork shall be so arranged as to be readily dismantled and removable from the cast concrete without shock, disturbance or damage. Where necessary, the formwork shall be so arranged that the soffit form, properly supported on props only, can be retained in position for such period as may be required by maturing Conditions or Specification. Approval of the formwork by the Engineer before concreting shall not relieve the Contractor of his responsibility to produce concrete with the Tolerances specified in Section 03300. B.
FORM LINING The type and treatment of any lining (plywood, metal, plastics etc.) to the forms shall be appropriate to the concrete finish required.
C.
CLEANING and TREATMENT FORMS All rubbish shall be removed from the interior of the forms in contact with the concrete. Forms shall be clean and treated with a suitable release agent, where applicable.
D.
PROJECTING REINFORCEMENTS, FIXING DEVICES Where holes are needed in forms to accommodate projecting reinforcement or fixing devices, care shall be taken to prevent loss of grout when concreting or damage when demoulding.
E.
CAST-IN FIXINGS Allowance shall be made to accommodate cast-in fixings as shown on the drawings or where directed by the Engineer.
F.
CONTROL of COLOR
Project No. MK-1204
Volume II
031000-4
SECTION 031000 CONCRETE FORMWORK ___________________________________________________________________________
Where the finished concrete is exposed the Contractor shall obtain each constituent material from a single consistent source. The aggregates shall be durable and free of any impurities that may cause staining. The mix proportions and the grading, particularly of the fine aggregate, shall be maintained constant. In formwork the same type of plywood or timber shall be used throughout similar exposed areas, and individual plywood sheets or sections of timber in large panels shall not be replaced. G.
RELEASE AGENTS Release agents for formwork shall be to the approval of the Engineer. Where a concrete surface is to be permanently exposed, only one agent shall be used throughout the entire area. Release contact with reinforcement shall be avoided.
H.
REMOVAL of FORMS: Formwork not supporting concrete, such as sides of beams, columns, walls, and similar parts of the work (vertical faces), may be removed not less than 24 hours after placing concrete provided concrete is sufficiently hard to be not damaged by form removal operations, and provided that curing and protection operations are maintained. Formwork supporting weight of concrete, such as slabs and other structural elements must remain in place for the time period shown in ACI 347, Section 3.6.2.3 (assuming design live load is less than dead load) and until concrete has attained design minimum 28 day compressive strength determined by field-cured specimens as defined below. Do not remove forms until the approval has been obtained from the Consultants. Determine the potential strength of in-place concrete by testing field-cured specimens representative of the concrete location of members, as specified in Section 033000 "CAST-IN-PLACE CONCRETE". Form facing materials may be removed not less than 4 days after placement, provided shores and other vertical supports have been arranged to permit removal of form facing material without loosening or disturbing shores and supports and provided concrete has achieved adequate compressive strength to safely support the load.
I.
TRIAL PANELS for FORMWORK When required by the Engineer the Contractor shall prepare, prior to concreting, a sample panel of size and surface texture to be agreed by the Engineer. The panel shall contain reinforcement fixed to represent the most congested part of the work. The panel shall be filled with the proposed concrete mix compacted by the method to be used in the work. As soon as practicable after compaction, the side forms shall be removed to enable the Engineer to check the surface finish and compaction achieved.
J.
SPRAYING
Project No. MK-1204
Volume II
031000-5
SECTION 031000 CONCRETE FORMWORK ___________________________________________________________________________
All surfaces of formwork which will be in contact with concrete, and all reinforcement, shall be damped with a fine spray of water immediately prior to concreting. K.
PROTECTION and CLEANING: 1.
Use all means necessary to protect workmen, passerby, the installed work and material of other trades, and complete safety of the structure.
2.
Cut nails, form ties, etc. off flush, and leave all surfaces smooth and clean.
3.
Remove metal spreader ties on exposed concrete by removing or snapping off inside the wall surfaces and pointing up and rubbing the resulting pockets to match surrounding surfaces.
4.
Flush all holes resulting from the spreader rods and sleeve nuts, using water, and the solidly pack throughout the wall thickness with cement grout applied under pressure by means of grouting gun; grout shall be one part cement to 2-1/2 parts sand; apply grout immediately after removing forms.
END OF SECTION
Project No. MK-1204
Volume II
031000-6
