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1、ACI 303R-04 supersedes ACI 303R-91 and became effective August 27, 2004. Copyright 2004, American Concrete Institute. All rights reserved including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or by electronic or mechanical device,
2、printed, written, or oral, or recording for sound or visual reproduc- tion or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors. ACI Committee Reports, Guides, Standard Practices, and Commentaries are intended for guidance
3、 in planning, designing, executing, and inspecting construction. This document is intended for the use of individuals who are competent to evaluate the significance and limitations of its content and recommendations and who will accept responsibility for the application of the material it contains.
4、The American Concrete Institute disclaims any and all responsibility for the stated principles. The Institute shall not be liable for any loss or damage arising therefrom. Reference to this document shall not be made in contract documents. If items found in this document are desired by the Architect
5、/Engineer to be a part of the contract documents, they shall be restated in mandatory language for incorporation by the Architect/Engineer. 303R-1 It is the responsibility of the user of this document to establish health and safety practices appropriate to the specific circumstances involved with it
6、s use. ACI does not make any representations with regard to health and safety issues and the use of this document. The user must determine the applicability of all regulatory limitations before applying the document and must comply with all applicable laws and regulations, including but not limited
7、to, United States Occupational Safety and Health Administration (OSHA) health and safety standards. Guide to Cast-in-Place Architectural Concrete Practice ACI 303R-04 This guide presents recommendations for producing cast-in-place architec- tural concrete. The importance of specified materials, form
8、ing, concrete placement, curing, additional treatment, and inspection, and their effect on the appearance of the finished product are discussed. Architectural concrete requires special construction techniques and materials, and each project will have special requirements. Specific recommendations an
9、d information presented in this guide should be used accordingly. Keywords: admixture; aggregate; architectural concrete; beam; bush- hammer; cement; coating; column; consolidation; cracking; curing; deflection; exposed-aggregate finish; finish; form lining; formwork; joint; joint sealant; mixture p
10、roportion; pigment; placing; quality control; release agent; repair; retarder; sealant; texture; wall. CONTENTS Chapter 1Introduction, p. 303R-2 Chapter 2Architectural considerations, p. 303R-2 2.1Architectural features 2.2Architectural design 2.3Coatings and sealers 2.4Joint sealants 2.5Specificati
11、ons Chapter 3Structural considerations, p. 303R-7 3.1Spalling 3.2Deflections 3.3Cracking 3.4Joints 3.5Beams and slabs 3.6Columns 3.7Walls Chapter 4Forms, p. 303R-9 4.1General 4.2Materials 4.3Economics 4.4Formwork accuracy 4.5Form joints 4.6Textures and patterns 4.7Formwork accessories 4.8Form coatin
12、gs and sealers Reported by ACI Committee 303 Daniel P. Dorfmueller Chair Keith AhalJerome H. FordRobert W. Nussmeier Doug BannisterChris A. ForsterJames M. Shilstone, Jr. George F. BatyThomas J. GrisingerMichael S. Smith Eugene H. Boeke, Jr.Robert P. HarrisDavid M. Suchorski Muriel BurnsG. P. Jum Ho
13、rstClaude B. Trusty, Jr. Joseph A. DobrowolskiRobert D. KirkGregory R. Wagner Greg Dobson Consulting member Louis Tallarico (deceased 2004), a former committee member, was a major contributor to this guide. 303R-2 ACI COMMITTEE REPORT 4.9Form release agents 4.10Form removal Chapter 5Reinforcement, p
14、. 303R-17 5.1General 5.2Clear space 5.3Reinforcement supports and spacers 5.4Tie wire 5.5Zinc-coated (galvanized) steel reinforcement 5.6Epoxy-coated reinforcing bars Chapter 6Concrete materials and mixture proportioning, p. 303R-19 6.1General 6.2Materials 6.3Proportioning, mixing, and temperature c
15、ontrol Chapter 7Placing and consolidation, p. 303R-21 7.1Conveying and placing 7.2Consolidation Chapter 8Curing, p. 303R-22 8.1General 8.2Curing in forms 8.3Moist curing 8.4Membrane curing 8.5Hot-weather curing Chapter 9Treated architectural surfaces, p. 303R-23 9.1Surface retarders 9.2High-pressure
16、 water jet 9.3Acid wash 9.4Abrasive blasting 9.5Tooling or other mechanical treatments Chapter 10Finishing and final cleanup, p. 303R-25 10.1General 10.2Tie holes 10.3Blemish repair 10.4Stain removal 10.5Sealers and coatings Chapter 11References, p. 303R-26 11.1Referenced standards and reports 11.2C
17、ited references Appendix AArchitectural concrete photos, p. 303R-29 CHAPTER 1INTRODUCTION Architectural concrete is concrete that will be permanently exposed to view and that requires special care in the selec- tion of the concrete materials, forming, placing, and finishing to obtain the desired arc
18、hitectural appearance. This guide presents recommendations for cast-in-place architec- tural concrete based on the information available to the committee. Various procedures are recommended for deter- mining initial requirements of the architect, contractor, concrete producer, and inspector. Critica
19、l areas are indicated for special attention, and means for prevention or correction of defects are discussed. Specific surface treatments and special forming techniques are presented. Applicable codes, specifications, and recommendations are cited throughout the text and listed in Chapter 11. Genera
20、l information is found in References 1, 2, and 3. The information presented in this guide is very broad and covers many special conditions for specific architectural concrete. Information that may be applicable for use in producing a specific result may not be applicable to another. The user should
21、also be aware that recommendations in this guide are subjective to the means and methods used for accomplishing a specific task for a specific level of architectural effect and should be tested before use to ensure it will produce the required result. Further research is needed to provide additional
22、 information on bugholes and other construction problems. This guide does not address all the problems associated with architectural concrete. CHAPTER 2ARCHITECTURAL CONSIDERATIONS 2.1Architectural features 2.1.1 General acceptance criteriaArchitecturally acceptable concrete surfaces should be aesth
23、etically compatible with minimal color and texture variations and minimal surface defects when viewed at a distance of approximately 20 ft (6 m) or more as agreed upon by the architect, owner, and contractor, or as otherwise specified. 2.1.2 MeasurementIt is beyond the scope of this guide to establi
24、sh precise or definitive rules of measurement. Within any discrete building element or series of like elements, however, a high degree of visual uniformity is generally expected and required. The preconstruction mockup panel would normally be used to establish acceptance criteria. Refer to Section 2
25、.5.4, Preconstruction mockup. 2.1.3 Variations in color and shadingThese are minimized by: Quality control of ingredients, concrete mixtures, and consistency (Sections 6.2, and 6.3); Uniform concrete delivery schedules (Section 7.1.1); Uniformity of form surface, form release agent, application rate
26、, and formwork reusage, erection, and stripping (Sections 4.8 through 4.10.4); Uniform rates of placement and consistent methods of placement and consolidation of concrete (Chapter 7); Placement schedules to minimize extreme variations of ambient conditions (Section 7.1.1); Uniform curing procedure
27、and material (Chapter 8); and Properly timed or executed finishing operations (Chapter 10). 2.1.4 FinishesSurface textures are grouped into two general classes: Untreated surfaces where the mortar is the principal visible constituent, and the texture is that which is imparted by the formwork sheathi
28、ng or form liner; and Surfaces that are mechanically treated in place by removal of surface mortar to expose the underlying aggregate, thus wholly or partially obscuring the texture of the form sheathing or form liner. CAST-IN-PLACE ARCHITECTURAL CONCRETE PRACTICE303R-3 High-build polymer coatings a
29、nd cementitious or polymer-modified coatings that obscure both color and texture are not included in this guide. 2.2Architectural design 2.2.1 General criteriaArchitectural design criteria for readily obtainable and acceptable results should include: Isolation or division of concrete surfaces to all
30、ow reuse of formwork modules by the incorporation of rustication or joint patterns, or by the employment of a paneled effect; Systematic planning of construction joints that allows a reusable formwork module and conforms to structural requirements; Use of textured form sheathing (face sheets) or for
31、m liners, mechanically or chemically textured concrete finishes, or other relief features; and Limitations on the size of panels bounded by rustication or joint patterns. (Large, smooth, uninterrupted expanses of concrete surfaces should be avoided.) 2.2.2 Details of architectural design 2.2.2.1 Unc
32、hamfered cornersAcute- and right-angle corners can be obtained. Proper consolidation of the concrete is essential and self-compacting concrete may be required to achieve a crisp edge (Fig. 2.1). Forms should be designed and sealed to resist concrete placing pressures, and fabricated such that they c
33、an be stripped without damaging the concrete. Extended stripping time will probably be necessary to prevent damage to sharp corners which, depending on the size of the project, may require additional forms. Extended stripping time could also affect color because variation in form stripping times wil
34、l increase the color differential. 2.2.2.2 Chamfered cornersWhere chamfers are part of the architectural feature, the chamfer form strip should be continuously tight to all form surfaces that they are in contact with. Plastic or metal chamfer strips are available that have integral means of sealing
35、to the form contact surfaces. Wood chamfer strips are difficult to maintain. 2.2.2.3 JointsPanel area joints may be recessed into the concrete surface by applying rustication strips on the formed surfaces. These may also be used for construction joints as needed by the contractor. Waterstops, keyway
36、s, and joint sealants may be included where required. Refer to Section 3.4 for recommended joint depths. Formwork rustication strips should have a draft of not less that 15 degrees to facilitate removal. Draft is defined as a small angle or taper in the formwork for reentrant formed surface that fac
37、ilitates release when the form is stripped, as shown in Fig. 2.2. Also, wooden strips should be deeply sawcut (kerfed) on the back side to prevent binding due to expansion from absorbed water. All rustication strips or other inserts should be installed tight to the form contact surface. Back-screwin
38、g the strip so it can be released before stripping may help obtain a tight seal. Nailing the strips to the form face for some architectural treatments may be acceptable but will not attain an absolutely tight seal. Insufficient nailing of the form strip will usually result in some leakage and leave
39、the reveal void ragged and discolored. Rustication strips should be uniform in dimensions, nonwater absorbent, and of sufficient stiffness to maintain alignment during concrete placement operations. In areas of possible deflection of the sheathing, a method of treatment to prevent mortar leakage sho
40、uld be used. Metal chamfer or rustication strips and other materials of similar stiffness should have a minimum width of 3/4 in. (20 mm). Widths of wooden rustication strips should be at least equal to their depths. Joints smaller than recommended above can be attained with special form detailing us
41、ing steel insert strips installed between the forms. Intersections of chamfer or rustication strips should be mitered or coped to fit snugly. Chamfer, rustication, or isolation strips may be placed so as to cover form joints. 2.2.2.4 SoffitsA drip should be installed in soffits near vertical surface
42、s where there is a potential for downward movement of rainwater on the vertical concrete face (Fig. 2.3). The drip molds should be placed as near to the external vertical face as practicable, but not closer than 1 in. (25 mm) from the finished concrete surface. Note that the drip in Fig. 2.3 is inte
43、rrupted at either end of the underside horizontal surface to encourage water to fall before it reaches the inside vertical face. 2.2.2.5 Sloped surfacesAccumulation of airborne solids on horizontal surfaces can be minimized by sloping Fig. 2.1(a) Difficult-to-achieve consolidation at acute corners;
44、and (b) the use of self-compacting concrete allows for proper consolidation at the acute corner. Fig. 2.2Typical construction joint/detail. 303R-4ACI COMMITTEE REPORT such surfaces. Sills should have a slight downward slope, and upper surfaces of recesses should have an upward slope from the horizon
45、tal relative to the inside face of the recess. Slopes may vary from 1:12 for smooth surfaces to 1:1 for textured surfaces (Fig. 2.4(a) and (b). On parapets, the slope should be away from the face. Unsloped horizontal offsets in vertical recesses and the use of textures on horizontal surfaces should
46、be avoided. If a horizontal recess is formed without a drip near the exterior face, a slight upward slope relative to the exterior face should be provided (Fig. 2.4(c). Sloped and horizontal surfaces cast against a form will trap air bubbles as the concrete is consolidated. Special techniques and ma
47、terials may be required to reduce trapped air, such as an absorbent form face. Refer to ACI 309R for more information. 2.2.3 Combination with precast concreteCast-in-place architectural concrete and precast elements may be success- fully combined in either of the two following ways, both of which re
48、quire detailed effort on the parts of the owner, architect, contractor, and inspector (Fig. 2.5): Color and texture may be reasonably matched by on-site precasting at the same time cast-in-place work is done, using the same concrete mixture, materials, formwork techniques, and curing for both types
49、of concrete. Provide for contrasting colors and textures in the design between off-site precast concrete and cast-in-place architectural elements. In some cases, color and texture can be closely matched using dissimilar materials. A mockup panel can be used to demonstrate the match for approval by the architect. Trying to achieve an exact match of cast-in-place concrete with precast units cast off-site is extremely difficult and may not be achievable in a cost-effective manner. Fig. 2.3Drip de
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