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1、:onal“ AC1 228.1 R-03 In-Place Methods to Estimate Concrete Strength Reported by AC1 Committee 228 american concrete institute PO, BOX 9094 FARMINGTON HILLS, MICHIGAN 48333-9094 Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=IHS Employees/1111111001, User=listm
2、gr, listmgr Not for Resale, 03/05/2007 01:54:21 MSTNo reproduction or networking permitted without license from IHS -,-,- First Printing, November 2003 In-Place Methods to Estimate Concrete Strength Most AC1 Standards and committee reports are gathered together in the annually revised AC1 Manual of
3、Concrete Practice. The sev- eral volumes are arranged to group related material together and may be purchased in- dividually or in setS.The AC1 Manual of Con- Crete Practice is also available on CD-ROM. AC1 Committees prepare standards and reports in the general areas of materials and properties of
4、concrete, construction practices and inspection, pavements and slabs, struc- tural design and analysis, structural specifica- tions, and special products and processes. A complete catalog of all AC1 publications is avai la bl e wit hou t charge. American Concrete Institute P.O. Box 9094 Farmington H
5、ills, MI 48333-9094 AC1 Certification Programs The final quality of a concrete structure depends on qualified people to construct it. AC1 certification pro- grams identify craftsmen, technicians, and inspectors who have demonstrated their qualifications. The follow- ing programs are administered by
6、AC1 to fulfill the grow- ing demand in the industry for certified workers: Concrete Flatwork Finisher Concrete Flatwork Technician Concrete Field Testing Technician-Grade I Enhancement of AC1 Documents The technical committees responsible for AC1 committee reports and standards strive to avoid ambig
7、uities, omis- sions, and errors in these documents. In spite of these efforts, the users of AC1 documents occasionally find information or requirements that may be subject to more than one interpretation or may be incomplete or incorrect. To assist in the effort for accuracy and clarity, the Technic
8、al Activities Committee solicits the help of indi- viduals using AC1 reports and standards in identifying and eliminating problems that may be associated with Concrete Strength Testing Technician Concrete Laboratory Testing Technician-Grade I their use. Users who have suggestions for the improvement
9、 of AC1 documents are reauested to contact the AC1 Engi- Concrete Laboratory Testing Technician-Grade il Concrete Construction Inspector Concrete Transportation Construction Inspector-ln- Training neering Department in writing, with the following infr- 1. Title and number of the document containing
10、the problem and specific section in the document; 2. Concise description of the problem; 3. If possible, suggested revisions for mitigating the The Institutes Engineering Staff will review and take appropriate action on all comments and suggestions received. Members as well as nonmembers of the Inst
11、i- tute are encouraged to assist in enhancing the accuracy and usefulness of AC1 documents. Concrete Construction Inspector-ln-Training mation: Concrete Transportation Construction Inspector problem. This document may already contain reference to these AC1 certification programs, which can be incorp
12、orated into project specifications or quality control procedures. If not, suggested guide specifications are available on request from the AC1 Certification Department. ISBN 0-87031-132-8 Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=IHS Employees/1111111001,
13、User=listmgr, listmgr Not for Resale, 03/05/2007 01:54:21 MSTNo reproduction or networking permitted without license from IHS -,-,- AC1 228.1 R-03 In-Place Methods to Estimate Concrete Strength Reported by AC1 Committee 228 Stephen P. Pessiki* Chair Farhad Ansari Hermenegildo Caratin Nicholas J. Car
14、ino* K. Choi Neil A. Cumrning Allen G. Davis Aldo Delahaza Ronald L. Dilly Donald E. Dixon Boris Dragunsky AI Ghorbanpoor* Frederick D. Heidbrink Bernard H. Hertlein Ka1 R. Hindo Robert S. Jenkins Keith E. Kesnert H. S. Lew Kenneth M. Lozen* Larry D. Olson John S. Popovics* Sandor Popovics Randall W
15、. Poston* Afshin Sadri Bryce P. Sirnons Patrick J. Sullivan George V. Teodoru Woodward L. Vogt Alexander B. Zoob *Members of the task force that prepared the revision +Task force Chair. Guidance is provided on the use of methods to estimate the in-place strength of concrete in new and existing const
16、ruction. The methods include: rebound number; penetration resistance, pullout, break-o8 ultrasonic pulse velocity, maturity, and cast-in-place cylinders. The principle, inherent limi- tations, and repeatability of each method are reviewed. Procedures are presented for developing the relationship nee
17、ded to estimate compressive strength from in-place results. Factors to consider in planning in-place tests are discussed, and statistical techniques to interpret test results are presented. The use of in-place tests for acceptance of concrete is intm- duced. The appendix provides information on the
18、number of strength levels that should be used to develop the strength relationship and explains a AC1 Committee Reports, Guides, Standard Practices, and Commentaries are intended for guidance in planning, designing, executing, and inspecting construction. This document is intended for the use of ind
19、ividuals 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 Institute disclaims any and ali responsibility for the stated principles. The Institute
20、 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 ArchitecuEngineer to be a part of the contract documents, they shall be restated in mandatory language for incorporati
21、on by the ArchitecuEngineer. It is the responsibility of the user of this document to establish health and safety practices appropriate to the specific circumstances involved with its use. AC1 does not make any representations with regard to health and safety issues and the use of this document. The
22、 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 to, United States Occupational Safety and Health Administration (OSHA) health and safety standards. regression analysi
23、s procedure that accounts for error in both dependent and independent variables. Keywords: coefficient of variation; compressive strength; construction; in-place tests; nondestructive tests; safety; sampling; statistical analysis. CONTENTS Chapter 1-Introduction, p. 228.1 R-2 1.1-Scope 1.2-Need for
24、in-place tests during construction 1.3-Influence of AC1 3 18 1.4-Recommendations in other AC1 documents 1.5-Existing construction 1 .6-Objective of report Chapter 2-Review of methods, p. 228.1 R-4 2.1-Introduction 2.2-Rebound number (ASTM C 805) 2.3-Penetration resistance (ASTM C 803K 803M) 2.4-Pull
25、out test (ASTM C 900) 2.5-Break-off number (ASTM C 1150) 2.6-Ultrasonic pulse velocity (ASTM C 597) 2.7-Maturity method (ASTM C 1074) 2.8-Cast-in-place cylinders (ASTM C 873) 2.9-Strength limitations 2.1Wombined methods 2.1 1-Summary AC1 228.1R-O3 supersedes AC1 228.1R-95 and became effective Septem
26、ber 16,2003. Copyright O 2003, 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, or recording for sound or visua
27、l reproduction or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors. 228.1 R-1 Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=IHS Employees/1111111001, User=listmgr, listmgr Not for R
28、esale, 03/05/2007 01:54:21 MSTNo reproduction or networking permitted without license from IHS -,-,- 228.1 R-2 AC1 COMMITTEE REPORT Chapter 3-Statistical characteristics of test results, p. 228.1 R-14 3.1-Need for statistical analysis 3.2-Repeatability of test results Chapter Bungey 1989; Malhotra a
29、nd Carino 1991). No attempt is made to review all of these methods in this report; only those methods that have been standardized by ASTM are discussed. Teodoru (1989) prepared a compilation of national standards on in-place test methods. 1.2-Need for in-place tests during construction In North Amer
30、ican practice, the most widely used test for concrete is the compressive strength test of the standard cylinder (ASTh4 C 3 1/C 3 1M). This test procedure is relatively easy to perform in terms of sampling, specimen preparation, and strength measurement. When properly performed, this test has low wit
31、hin-test variation and low interlaboratory variation and, therefore, readily lends itself to use as a stan- dard test method. The compressive strength so obtained is used to calculate the nominal strengths of structural members. Therefore, this strength value is an essential parameter in design code
32、s. When carried out according to standard procedures, however, the results of the cylinder compression test repre- sent the potential strength of the concrete as delivered to a site. The test is used mainly as a basis for quality control of the concrete to ensure that contract requirements are met.
33、It is not intended for determining the in-place strength of the concrete because it makes no allowance for the effects of placing, compaction, or curing. It is unusual for the concrete in a structure to have the same properties as a standard-cured cylinder at the same test age. Also, standard-cured
34、cylinders are usually tested for acceptance purposes at an age of 28 days; therefore, the results of these tests cannot be used to determine whether adequate strength exists at earlier ages for safe removal of formwork or the application of post-tensioning. The concrete in some parts of a structure,
35、 such as columns, may develop strength equal to the standard 28-day cylinder strength by the time it is subjected to design loads. Concrete in most flexural members (especially pretensioned flexural members) does not develop its 28-day strength before the members are required to support large percen
36、tages of their design loads. For these reasons, in-place tests are used to estimate the concrete strength at critical locations in a structure and at times when crucial construction operations are scheduled. Traditionally, some measure of the strength of the concrete in the structure has been obtain
37、ed by using field- cured cylinders prepared and cured in accordance with ASTM C 3 1/C 3 1M. These cylinders are cured on or in the Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=IHS Employees/1111111001, User=listmgr, listmgr Not for Resale, 03/05/2007 01:54:21
38、 MSTNo reproduction or networking permitted without license from IHS -,-,- IN-PLACE METHODS TO ESTIMATE CONCRETE STRENGTH 228.1 R-3 structure under, as nearly as possible, the same conditions as the concrete in the structure. Measured strengths of field- cured cylinders may be significantly differen
39、t from in-place strengths because it is difficult, and often impossible, to have identical bleeding, consolidation, and curing conditions for concrete in cylinders and concrete in structures (Soutsos et al. 2000). Field-cured specimens need to be handled with care and stored properly to avoid mislea
40、ding test results. Construction schedules often require that operations such as form removal, post-tensioning, termination of curing, and removal of reshores be carried out as early as possible. To enable these operations to proceed safely at the earliest possible time requires the use of reliable i
41、n-place tests to estimate the in-place strength. The need for such strength information is emphasized by several construction failures that possibly could have been prevented had in-place testing been used (Lew 1980; Carino et al. 1983). In-place testing not only increases safety but can result in s
42、ubstantial cost savings by permitting accelerated construction schedules (Bickley 1982a). 1.3-Influence of AC1 31 8 Before 1983, AC1 318 required testing of field-cured cylinders to demonstrate the adequacy of concrete strength before removal of formwork or reshoring. Section 6.2.2.1 of AC1 318-83 a
43、llowed the use of alternative procedures to test field-cured cylinders. The building official, however, must approve the alternative procedure before its use. Since 1983, AC1 3 18 has permitted the use of in-place testing as an alter- native to testing field-cured cylinders. The commentary to AC1 31
44、8-02 (Section R6.2) lists four procedures, which are covered in this Report, that may be used, provided there are sufficient correlation data (AC1 3 18R). Most design provisions in AC1 318 are based on the compressive strength of standard cylinders. Thus, to evaluate structural capacity under constr
45、uction loading, it is necessary to have an estimate of the equivalent cylinder strength of the concrete as it exists in the structure. If in-place tests are used, a valid relationship between the results of in-place tests and the compressive strength of cylinders must be established. At present, the
46、re are no standard practices for developing the required relationship. There are also no generally accepted guidelines for interpretation of in-place test results. These deficiencies have been impediments to widespread adoption of in-place tests. One of the objectives of this Report is to eliminate
47、some of these deficiencies. 1.4-Recommendations in other AC1 documents After the 1995 version of this Report was published, other AC1 documents incorporated in-place tests as alternative procedures for estimating in-place strength. One of these documents is AC1 301. In the 1999 version of AC1 301, P
48、aragraph 1.6.5.2 on in-place testing of hardened concrete includes the following: “Use of the rebound hammer in accordance with ASTM C 805, pulse-velocity method in accordance with ASTM C 597, or other nondestructive tests may be permitted by the Architecmngineer in evaluating the uniformity and rel
49、ative concrete strength in-place, or for selecting areas to be cored.” AC1 301-99 states in Paragraph 1.6.6.1 that the results of in-place tests “will be valid only if the tests have been conducted using properly calibrated equipment in accor- dance with recognized standard procedures and acceptable correlation between test results and concrete compressive strength has been established and is submitted.” Paragraph