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1、ACI 309R-05 became effective August 5, 2005 and supersedes ACI 309R-96. Copyright 2005, 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, p
2、rinted, written, or oral, or recording for sound or visual reproduction 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 in
3、 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. The
4、 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/En
5、gineer to be a part of the contract documents, they shall be restated in mandatory language for incorporation by the Architect/Engineer. 309R-1 Guide for Consolidation of Concrete Reported by ACI Committee 309 ACI 309R-05 Consolidation is the process of removing entrapped air from freshly placed con
6、crete. Several methods and techniques are available, the choice depending mainly on the workability of the mixture, placing conditions, and degree of air removal desired. Some form of vibration is usually employed. This guide includes information on the mechanism of consolidation and gives recommend
7、ations on equipment, characteristics, and procedures for various classes of construction. The paired values stated in inch-pound units and hard SI units are usually not exact equivalents. Therefore, each system is to be used independently of the other. Combining values from the two systems may resul
8、t in nonconfor- mance with this guide. Keywords: box out; compaction; consistency; consolidation; placing, rheology; rodding; segregation; spading; tamping; vibration; vibrator; workability. CONTENTS Chapter 1General, p. 309R-2 Chapter 2Effect of mixture proportions on consolidation, p. 309R-3 2.1Mi
9、xture proportions 2.2Workability and consistency 2.3Workability requirements Chapter 3Methods of consolidation, p. 309R-4 3.1Manual methods 3.2Mechanical methods 3.3Methods used in combination Chapter 4Consolidation of concrete by vibration, p. 309R-5 4.1Vibratory motion 4.2Process of consolidation
10、Chapter 5Equipment for vibration, p. 309R-6 5.1Internal vibrators 5.2Form vibrators 5.3Vibrating tables 5.4Surface vibrators 5.5Vibrator maintenance Neil A. CummingKenneth C. HoverH. Celik Ozyildirim Timothy P. DolenGarry R. MassSteven A. Ragan Chiara F. FerrarisBryant Mather*Mike Thompson Steven H.
11、 GeblerLarry D. OlsonBradley K. Violetta Glenn A. Heimbruch *Deceased. Richard E. Miller Chair Jerome H. Ford Subcommittee Chair 309R-2ACI COMMITTEE REPORT Chapter 6Forms, p. 309R-13 6.1General 6.2Sloping surfaces 6.3Surface blemishes 6.4Form tightness 6.5Forms for external vibration Chapter 7Recomm
12、ended vibration practices for general construction, p. 309R-15 7.1General 7.2Procedure for internal vibration 7.3Adequacy of internal vibration 7.4Vibration of reinforcement 7.5Revibration 7.6Form vibration 7.7Consequences of improper vibration Chapter 8Structural concrete, p. 309R-19 8.1Design and
13、detailing prerequisites 8.2Mixture requirements 8.3Internal vibration 8.4Form vibration 8.5Tunnel linings Chapter 9Mass concrete, p. 309R-20 9.1Mixture requirements 9.2Vibration equipment 9.3Forms 9.4Vibration practices 9.5Roller-compacted concrete Chapter 10Normal-density concrete floor slabs, p. 3
14、09R-22 10.1Mixture requirements 10.2Equipment 10.3Structural slabs 10.4Slabs on ground 10.5Heavy-duty industrial floors 10.6Vacuum dewatering Chapter 11Pavements, p. 309R-24 11.1General 11.2Mixture requirements 11.3Equipment 11.4Vibration procedures 11.5Special precautions Chapter 12Precast products
15、, p. 309R-27 12.1General 12.2Mixture requirements 12.3Forming material 12.4Choice of consolidation method 12.5Placing methods Chapter 13Structural low-density concrete, p. 309R-28 13.1General 13.2Mixture requirements 13.3Behavior of structural low-density concrete during vibration 13.4Consolidation
16、equipment and procedures 13.5Floors Chapter 14High-density concrete, p. 309R-29 14.1General 14.2Mixture requirements 14.3Placing techniques Chapter 15Self-consolidating concrete, p. 309R-29 15.1General Chapter 16Quality control and quality assurance, p. 309R-29 16.1General 16.2Adequacy equipment and
17、 procedures 16.3Checking equipment performance Chapter 17Consolidation of test specimens, p. 309R-31 17.1Strength 17.2Density 17.3Air content 17.4Consolidating very stiff concrete in laboratory specimens Chapter 18Consolidation in congested areas, p. 309R-32 18.1Common placing problems 18.2Consolida
18、tion techniques Chapter 19References, p. 309R-33 19.1Referenced standards and reports 19.2Cited references AppendixFundamentals of vibration, p. 309R-35 A.1Principles of simple harmonic motion A.2Action of a rotary vibrator A.3Vibratory motion in the concrete CHAPTER 1GENERAL Freshly placed unconsol
19、idated concrete contains excessive and detrimental entrapped air. If allowed to harden in this condition, the concrete will be porous and poorly bonded to the reinforcement. It will have low strength, high permeability, and poor resistance to deterioration. It may also have a poor appearance. The mi
20、xture should be consolidated if it is to have the properties desired and expected of concrete. Consolidation is the process of inducing a closer arrangement of the solid particles in freshly mixed concrete or mortar during placement by the reduction of voids, usually by vibra- tion, centrifugation (
21、spinning), rodding, spading, tamping, or some combination of these actions. Stiffer mixtures require greater effort to achieve proper consolidation. By using certain chemical admixtures (ACI 212.3R), consistencies requiring reduced consolidation effort can be achieved at lower water content. As the
22、water content of the concrete is reduced, concrete strength, perme- ability, and other desirable properties improve, provided that the concrete is properly consolidated. Alternatively, the GUIDE FOR CONSOLIDATION OF CONCRETE309R-3 cementitious materials content can be lowered, reducing the cost whil
23、e maintaining the same strength. If adequate consolidation is not provided for these stiffer mixtures, the strength of the in-place concrete decreases rapidly. Equipment and methods are now available for fast and efficient consolidation of concrete over a wide range of placing conditions. Concrete w
24、ith a relatively low water content can be readily molded into an unlimited variety of shapes, making it a highly versatile and economical construction material. When good consolidation practices are combined with good formwork and good form release agents, concrete surfaces have a highly pleasing ap
25、pearance (Fig. 1.1(a) through (c). CHAPTER 2EFFECT OF MIXTURE PROPORTIONS ON CONSOLIDATION 2.1Mixture proportions Concrete mixtures are proportioned to provide the workability needed during construction and the required properties in the hardened concrete. Mixture proportioning is described in ACI 2
26、11.1, 211.2, and 211.3R. 2.2Workability and consistency Workability of freshly mixed concrete determines the ease and homogeneity with which concrete can be mixed, placed, Fig. 1.1(a)Pleasing appearance of concrete in church construction. Fig. 1.1(b)Pleasing appearance of concrete in utility buildin
27、g construction. Fig. 1.1(c)Close-ups of surfaces resulting from good consolidation. 309R-4ACI COMMITTEE REPORT consolidated, and finished. Workability is a function of the rheological properties of the concrete. As shown in Fig. 2.1, workability may be divided into three main aspects: 1. Stability (
28、resistance to bleeding and segregation); 2. Ease of consolidation; and 3. Consistency, affected by the viscosity and cohesion of the concrete and angle of internal friction. Workability is affected by grading, particle shape, surface texture, proportions of aggregate and cement, use of pozzolan or g
29、round-granulated blast-furnace slag (GGBFS), chemical admixtures, air content, and water content of the mixture. Consistency is the relative mobility or ability of freshly mixed concrete to flow. It also largely determines the ease with which concrete can be consolidated. Once the materials and prop
30、ortions are selected, the primary control over workability is through variations in the water content or by adding a chemical admixture. The slump test (ASTM C 143) is widely used to indicate consistency of mixtures used in normal construction. The Vebe test (ASTM C 1170) is recommended for stiffer
31、mixtures. Values of slump, compacting factor, drop table spread, and Vebe time for the entire range of consistencies used in construction are given in Table 2.1. Other measures of consistency, such as the Powers remolding test and the concrete rheometers recently developed, are available. These meth
32、ods are infrequently used. The various consistency tests have been discussed by Neville (1981), Vollick (1966), and Ferraris (1999). 2.3Workability requirements The concrete should be sufficiently workable so that consoli- dation equipment, when properly used, will give adequate consolidation. A hig
33、h degree of ability to flow may be undesir- able because it may increase the cost of the mixture and reduce the quality of the hardened concrete. Where such a high degree of ability to flow is the result of too much water in the mixture, the mixture will generally be unstable and will probably segre
34、gate during the consolidation process. In mixtures that are highly plastic to flowing (Table 2.1), small nominal maximum-size aggregate and high content of fine aggregate are frequently used because the high degree of ability to flow means less work in placing. Mixtures such as these may have undesi
35、rable characteristics such as high shrinkage, cracking, and stickiness. At the other extreme, it is inadvisable to use mixtures that are too stiff for the intended conditions of consolidation. They will require great consolidation effort and even then may not be adequately consolidated. Direction, g
36、uidance, and trail mixtures are often required to achieve the use of mixtures of lower slump or fine aggregate content, or a larger nominal maximum-size aggregate, so as to give a more efficient use of the cement. Concrete containing certain chemical admixtures may be placed in forms with less conso
37、lidation effort. Refer to reports of ACI Committee 212 for additional information. The use of pozzolans or GGBFS may also affect the consolida- tion effort required to properly consolidate concrete. Refer to ACI 232.2R, 233R, and 234R for more information regarding these materials. The amount of con
38、solidation effort required with or without the use of chemical admix- tures and pozzolans or GGBFS should be determined by trial mixtures under field conditions. The workability of the mixture in the form determines the consolidation requirements. This workability may be consid- erably less than at
39、the mixer because of slump loss due to high temperature, premature stiffening, delays, or other causes. CHAPTER 3METHODS OF CONSOLIDATION The consolidation method should be compatible with the concrete mixture, placing conditions, form intricacy, and amount of reinforcement. Many manual and mechanic
40、al methods are available. 3.1Manual methods Plastic, highly plastic, and flowing consistency (Table 2.1) mixtures may be consolidated by rodding. Spading is some- times used at formed surfacesa flat tool is repeatedly inserted and withdrawn adjacent to the form. Coarse particles are shoved away from
41、 the form and movement of air voids toward the top surface is facilitated, thereby reducing the number and size of bugholes in the formed concrete surface. Hand tamping may be used to consolidate stiff mixtures. The concrete is placed in thin layers, and each layer is carefully Fig. 2.1Parameters of
42、 rheology of fresh concrete. Table 2.1Consistencies used in construction* Consistency description Slump, in. (mm)Vebe time, s Compacting factor average Thaulow drop table revolutions Extremely dry32 to 18112 to 56 Very stiff18 to 100.7056 to 28 Stiff 0 to 1 (0 to 25) 10 to 50.7528 to 14 Stiff plasti
43、c 1 to 3 (25 to 75) 5 to 30.8514 to 7 Plastic 3 to 5 (75 to 125) 3 to 0* 0.907 Highly plastic 5 to 7-1/2 (125 to 190) Flowing 7-1/2 plus (190 plus) 0.95 *Test method is of limited value in this range. GUIDE FOR CONSOLIDATION OF CONCRETE309R-5 rammed or tamped. This is an effective consolidation meth
44、od but is laborious and costly. The manual consolidation methods are generally only used on smaller nonstructural concrete placements and are labor intensive. 3.2Mechanical methods The most widely used consolidation method is vibration. Vibration may be either internal, external, or both. Power tamp
45、ers may be used to compact stiff concrete in precast units. In addition to the ramming or tamping effect, there is a low-frequency vibration that aids in the consolidation. Mechanically operated tamping bars are suitable for consol- idating stiff mixtures for some precast products, including concret
46、e masonry units. Equipment that applies static pressures to the top surface may be used to consolidate thin concrete slabs of plastic or flowing consistency. Concrete is literally squeezed into the mold, and entrapped air and part of the mixing water is forced out. Centrifugation (spinning) is used
47、to consolidate concrete in concrete pipe and other hollow sections and piles and poles. Many types of surface vibrators are available for slab construction, including vibrating screeds, vibratory roller screeds, plate and grid vibratory tampers, and vibratory finishing tools. Shock tables, sometimes
48、 called drop tables, are suitable for consolidating low-slump concrete. The concrete is deposited in thin lifts in sturdy molds. As the mold is filled, it is alternately raised a short distance and dropped on to a solid base. The impact causes the concrete to be rammed into a dense mass. Frequencies
49、 are 150 to 250 drops per min, and the free fall is 1/8 to 1/2 in. (3 to 13 mm). Smooth-drum vibratory rollers are commonly used to consolidate no-slump concrete mixtures. 3.3Methods used in combination Under some conditions, a combination of two or more consolidation methods gives the best results. Internal and external vibration can often be combined to advantage in precast work and occasionally in cast-in-place concrete. One scheme uses form vibrators for routine consoli
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