SECTION ARCHITECTURAL CONCRETE

Transcription

1 SECTION PART 1 - GENERAL 1.1 SUMMARY Section includes cast-in-place architectural concrete including form facings, reinforcement accessories, concrete materials, concrete mixture design, placement procedures, and finishes. 1. All exposed concrete shall be architectural grade, including site walls Related Requirements: 1. Division 07 Section "Joint Sealants" for elastomeric joint sealants in contraction and other joints in cast-in-place architectural concrete. 2. Division 32 Sections for concrete pavement and flatwork finishes. 1.2 SYSTEM DESCRIPTION Performance Criteria: 1. Provide formwork for architectural concrete with the intent to provide a smooth, glossy finish, upon removal of the form, with no patching, stoning, grinding, sacking or other form of repair and without the use of form release agents. Wash only. a. It is intended that forms shall impart a smooth uniform appearance to the concrete without mottles and color variations caused by non-uniform absorption of moisture or variation in temperature. 2. Formwork and shoring design shall be the sole responsibility of the Contractor. a. The design shall be in accordance with the recommendations of ACI 347. b. Ensure that the various members are not stressed more than allowed by the CBC for the material used. c. Design formwork and shoring to support full height lifts. d. Design formwork supports and bracing to support formwork panels without the use of through-wall form ties or any other penetrations of the waterproofing systems specified in Division 07 Sections. 3. Finish shall match required approved job mock-up. 4. Formwork for curved site walls shall be curved not straight segmental sections. Formwork Design Tolerance: 1. Tolerance: Reduce tolerances specified in Division 03 Section "Concrete Formwork" by 50 percent. 2. Tolerances shall be non-cumulative. 3. Provide architectural concrete per the requirements of this Section or Division 03 Section "Concrete Formwork" ACI 303R where more restrictive. Architect shall have final say over determining more-restrictive. 1.3 PREINSTALLATION MEETINGS Pre-installation Conference: Conduct conference at Project site

2 1. Before submitting design mixtures, review concrete design mixture and examine procedures for ensuring quality of concrete materials. Require representatives of each entity directly concerned with cast-in-place architectural concrete to attend, including the following: a. Contractor's superintendent. b. Independent testing agency responsible for concrete design mixtures. c. Ready-mix concrete manufacturer. d. Cast-in-place architectural concrete subcontractor. 1.4 SUBMITTALS Submit detailed shop drawings of the system, detailing all aspects of the form, including materials, tie systems and locations, embedded items and locations, form joints, corner joints, construction joints, leakage control, and all related details affecting Architectural quality. The shop drawings shall include floor plan diagrams indicating the intended sequencing and re-use of forms. Contractor shall submit formwork calculations signed by a KentuckyKentucky Civil Engineer. 1. Formwork details affecting Architectural finish quality shall be reviewed by the Architect. Mix Designs: As specified in Division 03 Section "Cast-in-Place Concrete except as modified for this Section. 1.5 QUALITY ASSURANCE Mockups: Provide vertical sample(s) representative of the formed concrete for approval by Architect. The locations shall be as approved by Architect. These shall be samples of conditions to be encountered in a column and site wall and in the building. Each item of the representative area shall be approved by Architect prior to its use in the remainder of the building. Include in the area the following typical items: 1. Forming, including form joints, corners, and rustications. 2. Form ties, where applicable. 3. Reinforcing of same complexity as job requirements. 4. Form coating and its application. 5. Concrete mix, including placing techniques, i.e., pumping, and lift height and duration between lifts. 6. Method of placing and vibrating concrete. 7. Curing of concrete. 8. Form removal. 9. Tie hole plugs, where applicable. 10. Surface finish and color. 1.6 PROJECT CONDITIONS Protect exposed formwork surfaces from moisture or direct sun. Cover form materials and protect from rain and moisture to prevent warping, buckling or other damage that may affect appearance or formwork performance. Protect exposed surfaces of architectural concrete formwork from weather, dirt, oil, rubbish, and stains prior to placement of concrete. Clean formwork surfaces in contact with concrete within 24 hours prior to placement of concrete. Verify dimensions prior to starting construction of forms. Survey bottom and tops of forms immediately prior to placement of concrete at each lift and adjust forms as necessary to achieve specified tolerances. Notify Architect of any discrepancies or inconsistencies

3 PART 2 - PRODUCTS 2.1 D. E. F. G. H. I. J. MATERIALS General: Comply with Division 03 Concrete Sections for formwork, embedded items, and shoring and re-shoring. Ties and Accessories: As specified in Division 03 Concrete Sections, except as noted below: 1. Form ties shall be adjustable type which does not leave an open hole through the concrete and which permits neat and solid patching at every hole. High strength taper ties or other type bolt-through ties, using plastic sleeve and neoprene cone for complete removal; snap ties not accepted. Provide lead plugs at exposed concrete tie holes. Grout tie holes at concealed areas and where noted. Drill tie holes from form face. 2. Form Tie Plugs at Building Columns and Beams: Lead plugs at form tie holes exposed to view. Bolts, rods and other devices when used for internal ties and spreaders shall be of such construction that when forms are removed, no metal shall be within 1-inch of the exterior concrete surface or within 1/2-inch of interior concrete surfaces. 3. Do not use wire ties and wood spreaders. Use plastic spreaders or approved equal that do not impart marks onto the finished concrete surface. 4. Accessories: Adjustable metal brackets, bolts, wedging devices, etc., for positive connection of form corners, panels, and lifting devices. All necessary elements for complete forming system. Concrete Materials and Mix: As specified in Division 03 Concrete Sections. Non-Shrink Grout: Factory non-shrink, non-metallic premixed grout; U.S. Grout Corp., "Five Star" or equal, colored to match colored concrete where exposed to view. Curing Compounds: ASTM C309, Type 1, clear resin type, free of oil, wax, grease, or other deleterious substance. Form Sealer: 1. NoxCrete "Pre-Form" or equal epoxy or aluminum polyurethane, non-staining, non transferring, as required to comply with design requirements for architectural concrete. 2. Form Sealer (Wood Forms): Form sealers shall be of a type which will not harmfully affect the appearance and/or utility of the concrete surface or the application of sealers. 3. Form sealer shall prevent the development of bond or adhesion to concrete. Form Joint Sealer: 1/4-inch closed cell PVC or uncured neoprene tape with pressure sensitive adhesive at each individual panel joint, form joint, corner, or cold joint reveal key. 1. Seal all formwork joints tightly to prevent leakage or washing out of cement mortar from concrete. Joist and Walers: High strength wood or aluminum joist system for maximum span between ties; slotted bottom flanges; integral nailer for attachment; for gang form system. Reveal and Chamfer Lumber: Extruded PVC specially produced for concrete work; Vinylex Corp., Preco Industries, or equal; milled clear Douglas fir, Pine, selected straight, sanded and sealed with penetrating sealer. 1. Material usage shall be consistent. 2. Do not use chamfer strips at corner architectural concrete unless approved or specified prior to casting by Architect. Blockouts and Keyways: Wood or Styrofoam

4 K. L. M. Accessories: Metal brackets, inserts, bolts, wedging devices, etc., for positive connection of form corners, panels and lifting devices. All necessary elements for complete framing system. Form Release Agents: It is the intent that architectural concrete be provided without use of form release. Should mock-up determine it is required, provide as follows: 1. Form release agents shall not discolor or change texture of finished concrete surface or inhibit proper application of any surface finishes or bonding agents. 2. Release Agent: a. Chemically reactive release agent that forms a soapy film between panel and concrete; spray apply and wipe off excess; follow manufacturer's instructions. b. Non-staining, for use on form specified, resulting in a clean, smooth finish. c. AtlasTechProductsœPremium GoldRelease,W.R.MeadowsDuoguardPlus orequal. Final acceptance of material is subject to approval of the Architect following use in mock-up panel. d. Form release agents containing diesel or other oils are not permitted. Clear Concrete Sealer: LM Scofield or equal, clear penetrating sealer, non-staining and non-darkening. 1. Apply at all architectural concrete enclosing indoor space, exposed to view or weather. PART 3 - EXECUTION 3.1 SURFACE CONDITIONS Commence Work when conditions are satisfactory. Discrepancies: 1. In the event of discrepancy or conflict, immediately notify the Architect. 2. Do not proceed with installation in areas of discrepancy until all such discrepancies have been fully resolved. 3.2 D. FORM CONSTRUCTION As specified in Section and as required to comply with specified design requirements. Provide forms complete and of such strength and adequately braced so as to prevent any spreading, shifting or settling when concrete is placed to ensure finished concrete surfaces of the required tolerances. 1. Formwork shall be able to withstand excessive deflection when filled with wet concrete. 2. Forms shall be tight to prevent leakage or washing out of cement mortar from concrete. 3. Provide additional bracing, shoring, and accessories as required to achieve specified tolerances. 4. Use extra studs, walers and bracing to prevent bowing of forms between studs and to avoid bowed appearance in concrete. Do not use narrow strips of form material which will produce bow. 5. Provide sealers, trim, corner bracing, stiffeners, to achieve profiles of joints and seams, as shown on Drawings. Formwork corner joints to be mechanically adjustable after erection as required to achieve tight seal and achieve specified tolerances. Layout:

5 Form all required cast-in-place concrete to the shapes, sizes, lines, and dimensions indicated on the Drawings. Exercise particular care in the layout of forms to avoid necessity for cutting of concrete after it is in place. Panel Attachment: See Drawings for layouts and details of architectural concrete. Provide as shown. a. Formwork panels and joints shall align vertically and horizontally within face of formwork assembly and between adjacent assemblies. b. Fabricate panel sizes so that panel joints occur at cold joints, rustications or bevel joints per layouts shown and as specified. c. Panel layout shall be uniform and regular with joint location subject to acceptance by Architect. Review is for Architectural features only as it affects visual appearance. d. Provide cold joint at transition between standard concrete and architectural concrete. e. Provide cold joint between columns and girders. f. Provide cold joints to coincide with location of rustications shown at architectural concrete site walls. g. Provide water stops at cold joints as specified in Division 07 Waterproofing sections. Perform all forming required for Work of other trades and do all cutting and repairing of forms required to permit such installation. a. Accurately place and securely support items to be built into forms. Carefully examine the Drawings and specifications and consult with other trades as required relative to provisions for openings, reglets, chases, and other items in the forms. See Drawings for boards, strips, or other methods of creating patterns and reveals on walls or columns. In these areas forms shall be such as to allow joints to occur in a reveal. Form Deflection: a. General: Accurately calculate anticipated deflections due to weight of fresh concrete. Securely brace against lateral deflections. Design forms to a maximum deflection of L/400. b. Camber: Where specifically shown, position forms to maintain lines and elevations, within specified tolerances measured from camber lines. Maintain to within 1/8-inch until re-shoring is removed. Make proper provision for all openings, offsets, recesses, anchorage, blocking, and other features of the Work as shown or required. Provide openings as required for vibrators and concrete placing. Use suitable whaler and tie system for vertical architectural grade concrete surfaces with additional strongbacks or reinforcement to achieve specified tolerances and to minimize quantity of tie holes. Install taper ties with barge end of taper toward inside of non-exposed face of concrete. Fabricate forms for easy removal without hammering or prying against concrete surfaces. a. Provide crush plateau or wrecking plates where stripping may damage cast concrete surfaces. b. Provide top forms for inclined surfaces where slope is too steep to place concrete with bottom form only. At round column formwork, locate joints away from view side. Coordinate location with Architect. E. Construction: 1. Quantity of form tie holes as required per formwork design and as specified in Division 03 Concrete Sections. 2. Tie Holes: a. Drill forms to suit ties used to provide snug fit and to prevent leakage of concrete mortar around tie holes. Do not splinter forms by driving ties through improperly prepared holes. Drill tie holes to provide snug fit of taper tie. b. Form tie holes shall align within panel face. c. Form tie holes shall be arranged symmetrically about panel face unless as otherwise required for stability of form. d. Align form tie holes between adjacent panels where practicable. e. At site walls, arrange tie holes to occur between reveals and control joints

6 f. Drill tie holes in panel from exposed face outward toward backside of form. Seal between face of tie cone and face of formwork to prevent leakage. All formwork shall be secured to joists and support framing from back side of form panel. Do not fasten through form face. Attachment: Screw formwork panels to joists and support framing. Nailing of form material is prohibited. Provide sharp, clean corners at intersection planes without visible offsets or edges. Back joints with extra studs or girts to maintain true square intersection. Make all form panel joints, tight butt joints with all edges true and square. Form molding shapes, recesses and projections with smooth finish materials, and install in forms with sealed joints to prevent displacement. Provide 3/4-inch chamfers at all vertical concealed edges unless shown or noted otherwise. All exposed concrete edges shall have square corners or be provided as shown on the Architectural Drawings. Kerf wood inserts for forming keyways, reglets, recesses and the like, to prevent swelling and assure ease of removal. Seal cut form panel edges, bevels and reveal lumber, and tie holes with two coats of a form sealer to retard moisture penetration. Apply 2 coats of form sealer in accordance with the manufacturer's recommendations. Apply form sealer to all contact surfaces and the holes. Lightly sand form panel between coats. Provide temporary openings where interior area of formwork is inaccessible for cleanout, for inspection before concrete placement, and for placement of concrete. a. Brace temporary closures and set tightly to forms to prevent loss of concrete mortar. b. Locate temporary openings on forms in as inconspicuous a location as possible, consistent with Project requirements. c. Form intersecting planes to provide true, clean-cut corners, with edge grain of plywood not exposed as form for concrete. Brace temporary openings and set tightly to forms to prevent leakage. Do not install inside forms until reinforcing installation has been inspected and approved. Holes shall be provided in the forms at the bottom for cleaning purposes and shall be left open until just before the concrete is poured. Keep forms sufficiently wetted to prevent joints from opening up before the concrete is placed. F. G. H. Wall Formwork Construction: 1. Provide rustication at all panel joints and cold joints as shown. 2. Provide continuous rustication strip at upper terminus of exterior wall waterproofing. 3. At sitewalls, locate tie holes to occur within rustication strips, and fill holes using colored non-shrink non-metallic grout to match colored concrete. Provide continuous vertical rustication at changes in wall elevation. Corner Treatment: Form corners of walls, beams and columns to produce square, smooth, solid, unbroken lines, except as otherwise shown. Tolerances: 1. Forms shall be built true to the required lines and so maintained until concrete has hardened sufficiently to permit removal. 2. Construct all bracing, supporting members, and centering of ample size and strength to safely carry, without excessive deflection, all dead and live load to which they may be subjected. 3. Forms shall have sufficient rigidity so as to resist deflection more than 1/8-inch between supports after the concrete has been place or L/400 whichever is less. 4. Ensure that embedded items are placed and held, during placing of concrete, to tolerances consistent with other items that will be attached to them

7 I. J. Adjustment of Forms: When a concrete pour has been stopped for a sufficient length of time so that shrinkage or warp has separated the forms and the concrete, provision shall be made to draw the forms into firm contact with the concrete before placing additional concrete. Care shall be taken to prevent any shoulder or ledge formed at a cold joint. Re-Use of Forms: 1. Except as specifically accepted in advance by the Architect, re-use of forms shall in no way delay or change the schedule for placement of concrete from the schedule obtained if all forms were new, nor shall quality, appearance, or performance of the final structure be reduced. 2. Clean and repair surfaces of forms to be re-used. The finished surface of the concrete shall not reflect any deterioration in the form due to re-use. Split, frayed, delaminated or otherwise damaged form facing materials shall be replaced. Apply new for release agent material to concrete contact surfaces as specified for new formwork. When forms are re-used for successive concrete placement, thoroughly clean surfaces, remove fins and laitance, and tighten forms to close all joints. Align and secure joints to prevent offsets. 3. Forms at architectural concrete shall be reused no more than 3 times. 3.3 FINISHES Smooth-Formed Finish: As-cast concrete texture imparted by form-facing material, arranged in an orderly and symmetrical manner with a minimum of seams. Remove fins and other projections exceeding specified limits on formed-surface irregularities. Repair and patch tie holes and defects. 3.4 SHORES AND BRACES Install shoring, re-shoring, and bracing as necessary to support construction loadings and as required to maintain specified tolerances. Comply with ACI 347. Provide additional shoring/bracing to ensure strict adherence to tolerances at architectural concrete. Install shoring, re-shoring, and bracing as necessary to support construction loadings and as required to maintain specified tolerances. Comply with ACI 347. Provide additional shoring/bracing to ensure strict adherence to tolerances at architectural concrete. Structural Drawings and Specifications represent the finished structure. They do not indicate method of construction, except where critical to the integrity of the finished structure. The Contractor shall provide all measures necessary to protect the structure during construction. Observation visits to the site by the Architect will not include review of such measures. 3.5 REMOVAL OF FORMS Time of form removal shall depend on the strength of the concrete and the curing. When concrete has been exposed to cold weather, curing has not been effective, or concrete strengths are lower than expected, defer form removal. The following time periods shall be considered a minimum with verification of strengths by control cylinders which may be extended if deemed necessary by the Architect. 1. As specified in Division 03 Concrete Sections 2. Leave forms in place for a minimum of 7 days, keeping them moist or as otherwise required to obtain suitable appearance to match approved mock-up

8 3.6 CURING Concrete shall be cured by liquid membrane-forming curing compounds as specified herein. Curing compounds shall not be used on surfaces when their use may be detrimental to bonding of concrete, calking and sealants, or the specified surface finish or coating. Curing Compound: 1. Application shall commence immediately following completion of specified finishing. 2. When applying compound, the surfaces shall be damp but shall be free from standing water. 3. Surfaces shall be covered with a uniform and even film of compound, as supplied, using pressurized spray equipment. 4. Apply in a single coat to achieve total coverage as recommended by manufacturer. 3.7 SEALING Seal exposed concrete above window areas to prevent alkaline from etching window glazing. Provide sealer at all architectural concrete surfaces exposed to weather. Apply sealer at inside of cold joints and rustications. 3.8 DEFECTIVE WORK Any concrete work not in accordance with the Contract Documents will be deemed defective including but not limited to: Work not formed as shown or not true to alignment or not plumb or level, or not true to the grades and level; that has voids or rock pockets; that has sawdust, wood or debris embedded in it; is not true to line and plane; is not thoroughly troweled and surfaces as specified; which does not meet specified tolerances or does not connect accurately to adjoining work. Remove and replace defective Work with workmanship complying with the Contract Documents at no additional cost or time. 3.9 PROTECTION Protect finished architectural concrete surfaces from subsequent damage during construction including temporary enclosures or panels. Protect all surface corners from damage. Do not apply field survey marks, erection marks or other writing to architectural concrete surfaces. END OF SECTION