ACI-209.1R-2005.pdf
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1、ACI 209.1R-05 became effective July 25, 2005. 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, printed, written, or oral,
2、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 planning, designing, exec
3、uting, 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 Concrete Institu
4、te 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 part of the
5、 contract documents, they shall be restated in mandatory language for incorporation by the Architect/Engineer. 209.1R-1 Report on Factors Affecting Shrinkage and Creep of Hardened Concrete Reported by ACI Committee 209 ACI 209.1R-05 This guide describes the effects of numerous variables on shrinkage
6、 and creep of hardened concrete, including mixture proportions, environment, design, and construction. This document is aimed at designers who wish to gain further information about factors changing shrinkage and creep but does not include information on the prediction of shrinkage and creep or stru
7、ctural design issues associated with shrinkage and creep. Keywords: creep; drying shrinkage; strain. CONTENTS Chapter 1Introduction, p. 209.1R-1 1.1Scope 1.2Terminology and range of values of strains 1.3Mechanisms of shrinkage and creep 1.4Areas of recommended research 1.5Additional sources Chapter
8、2Factors affecting drying shrinkage, p. 209.1R-5 2.1Introduction 2.2Effect of mixture proportions on drying shrinkage 2.3Effect of environment on drying shrinkage 2.4Effect of design and construction on drying shrinkage Chapter 3Factors affecting creep, p. 209.1R-8 3.1Introduction 3.2Effect of mixtu
9、re proportions on creep 3.3Effect of environment on creep 3.4Effect of construction and structural design on creep Chapter 4References, p. 209.1R-11 4.1Referenced standards and reports 4.2Cited references and reports CHAPTER 1INTRODUCTION 1.1Scope Factors affecting shrinkage and creep of hardened co
10、ncrete are presented to enable those involved in the evaluation and formulation of concrete mixtures to determine the effects of these factors. Section 1.2 of Chapter 1 defines terms used by those evaluating shrinkage and creep, while Chapters 2 and 3 describe effects of various factors on shrinkage
11、 and creep. This document does not include information on the prediction of shrinkage and creep or structural design issues associated with shrinkage and creep. Akthem A. Al-Manaseer*Mario A. ChiorinoMohsen A. IssaKlaus A. Rieder Zdenek P. BazantMarwan A. DayeHesham MarzoukIan Robertson Jeffrey J. B
12、rooksWalter H. DilgerBaquan MiaoKenji Sakata Ronald G. Burg*N. John Gardner*Harald S. MuellerNam K. Shiu Domingo J. CarreiraWill HansenLawrence C. NovakCarlos Videla *Members of subcommittee that prepared this report. David B. McDonald* Chair W. Jason Weiss Secretary 209.1R-2ACI COMMITTEE REPORT Thi
13、s document is not intended as a primary reference source for those studying shrinkage and creep; rather, it is aimed at designers who wish to gain further understanding of the effects of materials being used. This document also provides references that provide direction for those wishing to seek add
14、itional information about shrinkage and creep. 1.2Terminology and range of values of strains To discuss shrinkage and creep, it is important to define the following terms: Total strain; Shrinkage; Autogenous shrinkage; Drying shrinkage; Carbonation shrinkage; Swelling; Load-induced strain; Initial s
15、train at loading or nominal elastic strain; Creep strain; Basic creep; Drying creep; Compliance; Specific creep; and Creep coefficient. Various terms are shown in Fig. 1.1 and are described in detail below, together with an indication of typical value ranges. The values of total strain, shrinkage, a
16、nd creep are time-dependent. A thorough discussion of definitions, basic assumptions, and standard test methods for creep and shrinkage can be found in the references (RILEM TC 107- CSP 1998; Carreira and Burg 2000). Shrinkage and creep may occur in three dimensions; however, most research suggests
17、that total strain, shrinkage, and creep occur in each dimension independently. Thus, changes in length will be consistently used throughout this document, rather than changes in volume. 1.2.1 Total strainTotal strain is the total change in length per unit length measured on a concrete specimen subje
18、cted to a sustained constant load at uniform tempera- ture. As shown in Fig. 1.1, total strain is the sum of shrinkage and load-induced strain. 1.2.2 ShrinkageShrinkage is the strain measured on a load-free concrete specimen. Shrinkage does not include changes in length due to temperature variations
19、, but depends on the environment and on the configuration and size of the specimen. Shrinkage strain is usually measured by casting companion load-free specimens identical to the loaded concrete specimens used to measure the total strain. These companion specimens are cast from the same concrete bat
20、ch, have the same dimensions, and are stored in the same environment as the loaded concrete specimens. Shrinkage values are given as dimensionless strains (length change over a given length) expressed as percent, mm/mm, or in./in. It is common to describe shrinkage in microstrain or millionths, as t
21、he value of strain 106. Thus, 1000 microstrain is equivalent to 1 103 mm/mm. Values of long-term concrete shrinkage are typically between 200 and 800 106 mm/mm, (200 to 800 microstrain) (Zia, Ahmad, and Leming 1997) and mortar shrinkage typically between 800 and 2000 106 mm/mm (800 and 2000 microstr
22、ain) (Heath and Roesler 1999). Cement paste Fig. 1.1Relationship between various measured and derived strain values. The figure shows that the concrete undergoes autogenous shrinkage before drying. Once drying commences at time t0, drying shrinkage occurs. Upon loading, both drying and basic creep o
23、ccurs in the drying specimen. FACTORS AFFECTING SHRINKAGE AND CREEP OF HARDENED CONCRETE209.1R-3 shrinkage values are typically between 2000 and 6000 106 mm/mm (2000 and 6000 microstrain) (Feldman 1969). 1.2.3 Autogenous shrinkageThe shrinkage occurring in the absence of moisture exchange (as in a s
24、ealed concrete specimen) due to the hydration reactions taking place inside the cement matrix is termed autogenous shrinkage. Less commonly, it is termed “basic shrinkage” or “chemical shrinkage.” Autogenous shrinkage was almost never consid- ered as a factor in research on shrinkage and creep befor
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