1、ACI 214R-11Reported by ACI Committee 214Guide to Evaluation ofStrength Test Results of ConcreteGuide to Evaluation of Strength Test Results of ConcreteFirst PrintingApril 2011ISBN 978-0-87031-423-0American Concrete InstituteAdvancing concrete knowledgeCopyright by the American Concrete Institute, Fa
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10、 ACI standards and committee reports are gathered together in the annually revised ACI Manual ofConcrete Practice (MCP).American Concrete Institute38800 Country Club DriveFarmington Hills, MI 48331U.S.A.Phone: 248-848-3700Fax: 248-848-3701www.concrete.orgACI 214R-11 supersedes 214R-02 and was adopte
11、d and published April 2011.Copyright 2011, American Concrete Institute.All rights reserved including rights of reproduction and use in any form or by anymeans, including the making of copies by any photo process, or by electronic ormechanical device, printed, written, or oral, or recording for sound
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14、for the stated principles. The Instituteshall not be liable for any loss or damage arising therefrom.Reference to this document shall not be made in contractdocuments. If items found in this document are desired by theArchitect/Engineer to be a part of the contract documents, theyshall be restated i
15、n mandatory language for incorporation bythe Architect/Engineer.Guide to Evaluation ofStrength Test Results of ConcreteReported by ACI Committee 214ACI 214R-11Statistical procedures provide valuable tools for evaluating the results ofconcrete strength tests. Information derived from such procedures
16、is valuablein defining design criteria, specifications, and other parameters needed forstructural evaluation and repair. This guide discusses variations that occurin concrete strength and presents statistical procedures useful in interpretingthese variations with respect to specified testing and cri
17、teria.Keywords: coefficient of variation; concrete strength; normal distribution;required overdesign; quality control; standard deviation; statistical methods.CONTENTSChapter 1Introduction, p. 21.1Introduction1.2SummaryChapter 2Notation and definitions, p. 22.1Notation2.2DefinitionsChapter 3Variatio
18、ns in strength, p. 33.1General3.2Influence of batch-to-batch variations on concretestrength3.3Influence of within-batch variations on concretestrengthDavid J. Ackers Richard D. Gaynor Colin L. Lobo*Bryce P. SimonsMadasamy Arockiasamy Alejandro Graf John J. Luciano Luke M. SnellWilliam L. Barringer T
19、homas M. Greene Allyn C. Luke*Patrick J. E. SullivanF. Michael Bartlett*Gilbert J. Haddad Stephen S. Marchese Eugene Takhtovich*Jerrold L. Brown Kal R. Hindo Richard E. Miller Michael A. TaylorBryan R. Castles*Robert S. Jenkins Venkataswamy Ramakrishnan Roger E. VaughanJames E. Cook Alfred L. Kaufma
20、n Jr. D. V. Reddy Woodward L. Vogt*Ronald L. Dilly William F. Kepler David N. Richardson*Orville R. Werner IIDonald E. Dixon Michael L. Leming James M. Shilstone Jr.*Committee members who prepared this guide.Casimir Bognacki*ChairJerry ParnesSecretary2 GUIDE TO EVALUATION OF STRENGTH TEST RESULTS OF
21、 CONCRETE (ACI 214R-11)American Concrete Institute Copyrighted Materialwww.concrete.orgChapter 4Analysis of strength data, p. 44.1General4.2Statistical functions4.3Strength variations4.4Interpretation of statistical parameters4.5Standards of controlChapter 5Criteria, p. 85.1General5.2Data used to es
22、tablish minimum required averagestrength5.3Criteria for strength requirementsChapter 6Evaluation of data, p. 116.1General6.2Numbers of tests6.3Rejection of doubtful specimens6.4Additional test requirements6.5Quality-control charts6.6Additional evaluation techniquesChapter 7References, p. 167.1Refere
23、nced standards and reports7.2Cited referencesCHAPTER 1INTRODUCTION1.1IntroductionThis guide provides an introduction to the evaluation ofconcrete strength test results. Procedures described areapplicable to the compressive strength test results requiredby ACI 301, ACI 318, and similar specifications
24、 and codes.Statistical concepts described are applicable for the analysisof other common concrete test results, including flexuralstrength, slump, air content, density, modulus of elasticity,and other tests used for evaluating concrete and ingredientmaterials. This guide assumes that the concrete te
25、st resultsconform to a normal distribution.Most construction projects in the United States andCanada require routine sampling of concrete and fabricationof standard molded cylinders. These cylinders are usuallycast from a concrete sample taken from the discharge of atruck or a batch of concrete. The
26、y are molded and curedfollowing the standard procedures of ASTM C31/C31M andtested as required by ASTM C39/C39M. If the concrete is soprepared, cured, and tested, the results are the compressivestrength of the concrete cured under controlled conditions,not the in-place strength of the concrete withi
27、n the structure.It is expected that, given the uniformity of the curingconditions, these cylinders would have essentially the samestrength, thereby indicating concrete with consistent properties.It is these cylinders that are used for acceptance purposes.Inevitably, strength test results vary. Varia
28、tions in themeasured strength of concrete originate from two sources:Batch-to-batch variations can result from changes to theingredients or proportions of ingredients, water-cementi-tious material ratio (w/cm), mixing, transporting, placing,sampling of the batch, consolidating, and curing; andWithin
29、-batch variations, also called within-test variations,are primarily due to differences in sampling of thebatch sample, specimen preparation, curing, andtesting procedures.There are differences in individual mixer batches betweenthe front and rear of the mixer, as recognized by ASTMC94/C94M. For this
30、 reason, ACI Field Level I Techniciansare trained to make composite samples from the centralportions of loads.Conclusions regarding concrete compressive strength canbe derived from a series of tests. The characteristics ofconcrete strength can be accurately estimated when anadequate number of tests
31、are conducted in accordance withstandard practices and test methods.Statistical procedures provide valuable tools when evaluatingstrength test results. Information derived from them is alsovaluable in refining design criteria and specifications. Thisguide discusses variations in concrete strength an
32、d presentsstatistical procedures useful for interpreting them withrespect to specified testing and acceptance criteria.For the statistical procedures described in this guide to bevalid, data should be derived from samples obtained througha random sampling plan. Random sampling is when eachvolume of
33、concrete has an equal chance of being selected. Toensure this condition, selection should be made by using anobjective mechanism, such as a table of random numbers.When sample batches are selected on the basis of thesamplers judgment, biases are likely to be introduced that willinvalidate the analys
34、is. Natrella (1963), Box et al. (2005), andASTM D3665 discuss the need for random sampling, andprovide a useful short table of random numbers.1.2SummaryThis guide begins with a discussion in Chapter 3 of thebatch-to-batch sources of variability in concrete production,followed by the within-batch sou
35、rces of variability. Chapter 4presents the statistical tools that are used to analyze andevaluate concrete variability and determine compliance witha given specification. Chapters 5 and 6 review statistically-based specifications.CHAPTER 2NOTATION AND DEFINITIONS2.1Notationd2= factor for computing w
36、ithin-batch standarddeviation from average range (Table 4.1)fc = specified compressive strength of concrete, psi(MPa)fcr = required average compressive strength of concrete(to ensure that no more than a permissibleproportion of tests will fall below the specifiedcompressive strength) used as the bas
37、is for selectionof concrete proportions, psi (MPa)M =the median of a distribution, that is, half the valuesabove and half the values belown = number of tests in a recordR = within-batch rangeR = average range= maximum average range, used in certain controlchartsRmGUIDE TO EVALUATION OF STRENGTH TEST
38、 RESULTS OF CONCRETE (ACI 214R-11) 3American Concrete Institute Copyrighted Materialwww.concrete.orgs = sample standard deviation, an estimate of thepopulation standard deviation, also termed soveralls = statistical average standard deviation, or “pooled”standard deviations1= sample within-batch sta
39、ndard deviation, alsotermed swithin-batchs2= sample batch-to-batch standard deviation, alsotermed sproducerV = coefficient of variationV1= within-batch coefficient of variationX = average of strength test results, also called themeanXi= a strength test resultz = constant multiplier for standard devi
40、ation s thatdepends on number of tests expected to fall belowfc (Table 5.3) = population mean = population standard deviation1= population within-batch standard deviation2= population batch-to-batch standard deviation2.2DefinitionsACI provides a comprehensive list of definitions throughan online res
41、ource, “ACI Concrete Terminology,”http:/terminology.concrete.org. Definitions provided hereincomplement that panion cylinderscylinders made from the samesample of concrete.concrete samplea portion of concrete, taken at onetime, from a single batch or single truckload of concrete.individual strength(
42、also known as single cylinderstrength) is the compressive strength of a single cylinder(ASTM C39/C39M); a single cylinder strength is part of, butindividually does not constitute, a test result.normal distributiona frequently occurring naturaldistribution that has predictable properties. The analysi
43、s ofstrength test results presented in this guide assumes that thetest results under consideration are normally distributed.Although this assumption is reasonable, it is not always thecase; users should check the actual distribution of the data toensure it is reasonably close to normally distributed
44、.single cylinder strength(also known as individualstrength) is the compressive strength of a single cylinder(ASTM C39/C39M); a single cylinder strength is part of, butindividually does not constitute, a test result.strength test or strength test resultthe averagecompressive strength of two or more s
45、ingle-cylinderstrengths of companion cylinders tested at the same age.test recorda collection of strength test results from asingle concrete mixture.within-batch rangethe difference between themaximum and minimum strengths of individual concretespecimens that comprise one strength test result. Somet
46、imescalled the within-test range. When referring to a test of twocylinders, the within-batch range is sometimes called thepair-difference.CHAPTER 3VARIATIONS IN STRENGTH3.1GeneralThe variations in the strength of concrete test specimenscan be traced to two fundamentally different sources:1. Variabil
47、ity in strength-producing properties of the concretemixture and production process, some causes of which are listedunder the batch-to-batch variations in Table 3.1; and2. Variability in the measurement of strength comingfrom the testing procedures detailed in the within-batchvariations column of Tab
48、le 3.1.Variation in measured characteristics may be random orassignable depending on the cause. Random variation isnormal for any process; a stable process will show onlyrandom variation. Assignable causes represent systematicchanges typically associated with a shift in a fundamentalstatistical char
49、acteristic, such as mean, standard deviation,coefficient of variation, or other statistical measure. Thestandard deviation is the most commonly used indicator ofdata scatter around the mean. However, it is often moreinformative to use the coefficient of variation whencomparing variability in data between two sets of resultswith markedly different mean strengths.3.2Influence of batch-to-batch variationson concrete strengthFor a given set of raw materials, concrete strength islargely governed by the water-cementitious mater
