1、Guide to Identification and Control of Visible Surface Effects of Consolidation on Formed Concrete SurfacesReported by ACI Committee 309ACI 309.2R-15First PrintingFebruary 2015ISBN: 978-1-942727-03-3Guide to Identification and Control of Visible Surface Effects of Consolidation on Formed Concrete Su
2、rfacesCopyright by the American Concrete Institute, Farmington Hills, MI. All rights reserved. This material may not be reproduced or copied, in whole or part, in any printed, mechanical, electronic, film, or other distribution and storage media, without the written consent of ACI.The technical comm
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11、ing ACI.Most ACI standards and committee reports are gathered together in the annually revised ACI Manual of Concrete Practice (MCP).American Concrete Institute38800 Country Club DriveFarmington Hills, MI 48331Phone: +1.248.848.3700Fax: +1.248.848.3701www.concrete.orgThis document provides guideline
12、s for identifying and controlling visible effects on the surface of concrete as it relates to consoli-dation on precast or cast-in-place-formed concrete surfaces. A perfectly homogenous and blemish-free concrete element is diffi-cult, if not impossible, to achieve. This document, therefore, does not
13、 define an acceptable level of quality, as this should be defined in the contract documents.This guide explores the direct and indirect cause-and-effect rela-tionships, as well as other factors, concerning concrete surface appearance. Photographs are included in this document to illus-trate typical
14、concrete surface finish effects that are a departure from absolute perfection. Negative surface effects in concrete can be minimized by proper planning during the design and specifica-tion stages. Significant consolidation factors that minimize unde-sirable concrete negative surface effects are also
15、 discussed.Keywords: bugholes; consistency; consolidation; construction joints; discoloration; form offset; formwork (construction); layer lines; mixture proportioning; plastic settlement cracking; preplaced-aggregate concrete; quality control; sand streaking; surface air voids; surface defects; vib
16、ration; workability.CONTENTSCHAPTER 1INTRODUCTION AND SCOPE, p. 21.1Introduction, p. 21.2Scope, p. 2CHAPTER 2DEFINITIONS, p. 22.1Definitions, p. 2CHAPTER 3FACTORS CAUSING NEGATIVE SURFACE EFFECTS, p. 23.1General causes of negative surface effects, p. 23.2Design considerations of structural members,
17、p. 23.3Specifications, p. 43.4Forms, p. 43.5Properties of fresh concrete, p. 63.6Placement, p. 73.7Consolidation, p. 73.8Special construction conditions, p. 7CHAPTER 4NEGATIVE SURFACE EFFECTS, p. 84.1Honeycomb, p. 84.2Air voids in formed surfaces, p. 84.3Formstreaking, p. 84.4Aggregate transparency,
18、 p. 84.5Color variation, p. 84.6Sand streaking, p. 94.7Layer lines, p. 9Patrick F. OBrien Jr., ChairACI 309.2R-15Guide to Identification and Control of Visible Surface Effects of Consolidation on Formed Concrete SurfacesReported by ACI Committee 309Timothy P. DolenChiara F. FerrarisJohn F. Gibbons*G
19、lenn A. HeimbruchVincent E. Hunt*Gary R. MassRichard E. MillerLarry D. OlsonH. Celik OzyildirimSteven A. RaganBradley K. ViolettaConsulting MembersJerome H. FordDonald L. Schlegel*Revision Committee members.ACI Committee Reports, Guides, and Commentaries are intended for guidance in planning, design
20、ing, 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 American Concret
21、e 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/Engineer to be a par
22、t of the contract documents, they shall be restated in mandatory language for incorporation by the Architect/Engineer.ACI 309.2R-15 supersedes ACI 309.2R-98 and was adopted and published February 2015.Copyright 2015, American Concrete Institute.All rights reserved including rights of reproduction an
23、d use in any form or by any means, including the making of copies by any photo process, or by electronic or mechanical device, 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
24、 from the copyright proprietors.14.8Form offsets, p. 94.9Plastic settlement cracking, p. 9CHAPTER 5MINIMIZING NEGATIVE SURFACE EFFECTS, p. 9CHAPTER 6CONCLUSION, p. 10CHAPTER 7REFERENCES, p. 10Cited references, p. 10CHAPTER 1INTRODUCTION AND SCOPE1.1IntroductionThis guide is a reference source for sp
25、ecifiers, design engi-neers, architects, contractors, and other professionals who work with concrete surface finish of formed surfaces. The ability to identify or categorize negative surface effects is the first step in detecting the root cause of them. The goal of this guide is to differentiate bet
26、ween various negative surface effects to improve the concrete process and subse-quent concrete quality. The cause of negative concrete surface effects is sometimes not correctly diagnosed. For example, air voids are usually attributed to lack of vibration in circumstances where the correct source of
27、 the imperfec-tion is ill-prepared formwork or improper selection of the form-release agent. With misdiagnosis, negative surface effects are likely to occur again because appropriate correc-tive actions have not been identified and taken.This guide includes a summary of direct and indirect causes of
28、 negative surface effects in concrete surface finishes, along with photographs to illustrate them. The most serious effects resulting from ineffective consolidation procedures are also reviewed. They include honeycomb, cold joints, and exces-sive surface voids. A detailed description of these occur-
29、rences and their causes are provided. Of equal importance is the employment of properly trained and motivated supervi-sory and nonsupervisory construction personnel to achieve the intended concrete finishes and surface textures. Extreme negative surface effects do not always conform to the accept-ab
30、le limits required by contract documents and might be considered defective work. Methods for minimizing surface effects are also discussed.1.2ScopeThis guide does not define an acceptable level of quality, as this should be determined by the parties involved with the project. A perfectly formed conc
31、rete surface, uniformly smooth or deeply textured and essentially free of negative surface effects and color variation, is impossible to attain. Repairs to concrete surfaces are costly and difficult. The best repair work will not be as good as an original prop-erly finished surface. Every effort sho
32、uld be made before and during construction to minimize repairs by establishing and maintaining quality concrete operations and adhering to acceptable consolidation procedures for producing formed concrete work. Concrete construction procedures and project costs do not always provide the conditions n
33、ecessary to consistently obtain perfectly homogenous concrete free of all negative surface effects. Several negative surface effects discussed in this guide are tolerable and inherent in concrete production. Other potential causes of such negative surface effects may exist beyond those listed in thi
34、s report. It is the responsibility of the specifier to indicate in the contract docu-ments what constitutes acceptable and unacceptable nega-tive surface effects for the various surfaces to be produced under the terms of a given contract. Surface tolerance speci-fications can be found in ACI 347.3R-
35、13, Table 3.1.To achieve any concrete finish, the designer and contractor should use the most appropriate materials and design and construction practices to minimize negative surface effects and keep them within acceptable limits. This guide should not be used as a standard for surface finishes, but
36、 rather as a guide for the identification of surface effects and their causes. Because concrete consolidation is considered an established field, current research is limited.CHAPTER 2DEFINITIONS2.1DefinitionsACI provides a comprehensive list of definitions through an online resource, “ACI Concrete T
37、erminology,” http:/www.concrete.org/tools/concreteterminology.aspx.radius of influenceplan-view-area that a vibrator is able to produce sufficient impulses to consolidate concrete.CHAPTER 3FACTORS CAUSING NEGATIVE SURFACE EFFECTS3.1General causes of negative surface effectsTable 3.1 presents the pri
38、mary causes of surface condi-tions that factor into the resulting negative surface effects for the following factors: member design, formwork, construc-tion conditions, concrete properties, placement, and consoli-dation. Examples of common negative surface effects are illustrated in Fig. 3.1a throug
39、h 3.1i. The causes of negative surface effects on formed concrete surfaces are described in Table 3.1.3.2Design considerations of structural membersCommon problems requiring consideration during design and planning are congested reinforcementin particular, splices, narrow sections, or complex form c
40、onfigurations. Conditions that require closed top forming, embedments, and battered forms also require consideration during design and planning. Figure 3.2 features a dense matrix of pipe inserts and illustrates the importance of having a consolida-tion plan well in advance of production.To produce
41、properly consolidated concrete with the desired appearance, placement and consolidation of concrete should be understood. The designer should have working knowl-edge of the concrete placement process. The designer and constructor should communicate during early phases of the concreting process. Earl
42、y recognition of problem areas will allow enough time to take remedial measures, such as stag-gering splices, grouping reinforcing steel, modifying stirrup American Concrete Institute Copyrighted Material www.concrete.org2 CONTROL OF VISIBLE SURFACE EFFECTS OF CONSOLIDATION ON FORMED CONCRETE SURFAC
43、ES (ACI 309.2R-15)Table 3.1Causes of negative surface effects on formed concrete surfacesOccurrence: honeycombDescription: stony area with air voids; lacking of finesDesign of members Forms Construction conditions Properties of fresh concrete Placement Consolidation Highly congested reinforcement Na
44、rrow form geometry Reinforcement splices Leaking at joints Severe grout loss Premature setting Reinforcement too close to forms Lack of vibration access Congestion due to splices Insufficient fines Low workability Early stiffening Excessive mixing Oversized aggregate Excessive free-fall Excessive co
45、ncrete lifts Drop chute omitted Tremie too small Segregation due to horizontal movement Vibrator too small Incorrect frequency and amplitude Short immersion duration Excessing vibrator spacing Inadequate penetration Insufficient number of vibratorsOccurrence: air surface voidsDescription: small indi
46、vidual holes of irregular size and shape ranging up to 1 in. (25 mm) in diameterDesign of members Forms Construction conditions Properties of fresh concrete Placement Consolidation Battered or interfering construct Form face impermeable Poor wetting properties Formwork too flexible Improper form-rel
47、ease agent Improperly applying form-release agent Excessive release agent High concrete temperature Low FM of fine aggregate Fine aggregate with a high FM Low workability Excessive cement or pozzolan Particle degradation Excessive sand High air content Too slow Inadequate pumping rate Undersized buc
48、ket Amplitude too large External vibration inadequate Head of vibrator partially immersedOccurrence: form streakingDescription: fine aggregate or coarse aggregate textured areas lacking cement and usually with a dark color on adjacent surfaceDesign of members Forms Construction conditions Properties
49、 of fresh concrete Placement ConsolidationNA Leaking at joints or tie holes caused by loose hardware Usually caused by horizontal concrete movement Excess water or high slump Improper timing between placing and vibrating Excessive amplitude or frequencyOccurrence: aggregate transparencyDescription: dark or light areas of similar size and shape to that of the coarse aggregate; distinct mottled appearanceDesign of members Forms Construction conditions Properties of fresh concrete Placement Conso
