1、April 2014 Normenausschuss Bauwesen (NABau) im DINPreisgruppe 20DIN Deutsches Institut fr Normung e. V. Jede Art der Vervielfltigung, auch auszugsweise, nur mit Genehmigung des DIN Deutsches Institut fr Normung e. V., Berlin, gestattet.ICS 03.120.30; 91.100.30Zur Erstellung einer DIN SPEC knnen vers
2、chiedene Verfahrensweisen herangezogen werden: Das vorliegende Dokument wurde nach den Verfahrensregeln eines Fachberichts erstellt.!%,r“2097957www.din.deDDIN CEN/TR 16369Anwendung von Qualittsregelkarten bei der Herstellung von Beton;Englische Fassung CEN/TR 16369:2012Use of control charts in the p
3、roduction of concrete;English version CEN/TR 16369:2012Utilisation des cartes de contrle pour la production du bton;Version anglaise CEN/TR 16369:2012Alleinverkauf der Spezifikationen durch Beuth Verlag GmbH, 10772 Berlin www.beuth.deGesamtumfang 53 SeitenDIN SPEC 18769DIN CEN/TR 16369 (DIN SPEC 187
4、69):2014-04 2 Nationales Vorwort Dieses Dokument (CEN/TR 16349:2012) wurde vom Technischen Komitee CEN/TC 104 Beton und zuge-hrige Produkte“ erarbeitet, dessen Sekretariat von DIN (Deutschland) gehalten wird. Der fr die deutsche Mitarbeit zustndige Arbeitsausschuss ist der als Spiegelausschuss einge
5、setzte Arbeitsausschuss NA 005-07-02 AA Betontechnik“ des DIN-Normenausschusses Bauwesen (NABau). Dieses Dokument enthlt unter Bercksichtigung des DIN-Prsidialbeschlusses 1/2004 und der Entscheidung der zustndigen Gremien im Normenausschuss Bauwesen (NABau) die Englische Fassung des Fachberichts CEN
6、/TR 16369:2012. Es wird auf die Mglichkeit hingewiesen, dass einige Texte dieses Dokuments Patentrechte berhren knnen. Das DIN und/oder die DKE sind nicht dafr verantwortlich, einige oder alle diesbezglichen Patentrechte zu identifizieren. TECHNICAL REPORT RAPPORT TECHNIQUE TECHNISCHER BERICHT CEN/T
7、R 16369 October 2012 ICS 91.100.30; 03.120.30 English Version Use of control charts in the production of concrete Utilisation des chartes de contrle pour la production du bton Anwendung von Qualittsregelkarten bei der Herstellung von Beton This Technical Report was approved by CEN on 20 May 2012. It
8、 has been drawn up by the Technical Committee CEN/TC 104. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
9、 Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: Avenue Marnix 17, B-1000 B
10、russels 2012 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. CEN/TR 16369:2012: ECEN/TR 16369:2012 (E) 2 Contents Page Foreword 4Introduction .51 Scope 72 Symbols and abbreviations 73 Statistics for Concrete 83.1 Normal distribution o
11、f strength 83.2 Characteristic strength and target strength .83.3 Standard deviation 103.4 Setting the target strength . 134 Simple Data Charts . 145 Shewhart Charts . 155.1 Introduction . 155.2 Shewhart action criteria . 165.2.1 Points beyond UCL or LCL 165.2.2 Points beyond UWL or LWL 165.2.3 Patt
12、erns within control limits 165.3 Control of standard deviation 165.4 Example Shewhart chart 165.5 Modified application of Shewhart control chart 176 CUSUM . 196.1 Introduction . 196.2 Controlling mean strength . 226.3 Controlling standard deviation 226.4 Controlling correlation . 236.5 Design of V-m
13、ask 246.6 Action following change 247 Multivariable and Multigrade Analysis . 267.1 General . 267.2 Multivariable 267.3 Multigrade 278 Speeding the Response of the System 288.1 Early age testing . 288.2 Family of mixes concept 289 Guidance on Control Systems 309.1 Abnormal Results . 309.2 Handling m
14、ixes outside the concrete family . 309.3 Handling mixes not controlled by compressive strength requirements 319.4 Test rates . 329.5 Action following change 3310 EN 206-1 Conformity Rules for Compressive Strength 3310.1 Basic requirements for conformity of compressive strength 3310.2 Assessment peri
15、od . 3410.3 Conformity rules for compressive strength . 3410.4 Achieving an AOQL of 5 % with CUSUM 3610.5 Non-conformity . 3711 Implementing Control Systems . 3812 CUSUM Example . 38DIN CEN/TR 16369 (DIN SPEC 18769):2014-04 CEN/TR 16369:2012 (E) 3 12.1 Reference mix and concrete family . 3812.2 Main
16、 relationship . 3912.3 Applying adjustments . 4012.4 CUSUM calculation 4112.5 CUSUM action following change . 4512.6 Further data and a change in standard deviation 47Bibliography 51DIN CEN/TR 16369 (DIN SPEC 18769):2014-04 CEN/TR 16369:2012 (E) 4 Foreword This document (CEN/TR 16369:2012) has been
17、prepared by Technical Committee CEN/TC 104 “Concrete and related products”, the secretariat of which is held by DIN. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying
18、any or all such patent rights. DIN CEN/TR 16369 (DIN SPEC 18769):2014-04 CEN/TR 16369:2012 (E) 5 Introduction It is safe to assume that ever since manufacturing commenced, attempts have been made to control the process in order to improve quality and drive down costs. The application of statistical
19、techniques to manufacturing was first developed by physicist Walter A. Shewhart of the Bell Telephone Laboratories in 1924. Shewhart continued to develop the idea and in 1931 he published a book on statistical quality control 1. Shewhart recognised that within a manufacturing process there were not
20、only natural variations inherent in the process, which affected quality but there were also variations that could not be explained. Shewhart recognised that it is possible to set limits on the natural variation of any process so that fluctuations within these limits could be explained by chance caus
21、es, but any variation outside of these limits, special variations, would represent a change in the underlying process. Shewharts concept of natural and special variations is clearly relevant to the production of concrete at a ready-mixed plant or precast factory and the requirement to achieve a spec
22、ified compressive strength. Natural variations exist in the process due to variation in the raw materials (aggregate grading, chemical composition, etc), batching accuracy, plant performance, sampling and testing, etc. Special causes of variation outside of the natural variations could be due to cha
23、nged constituent materials being used, weigh-scales losing accuracy, a new batcher, problems with testing equipment, etc. Control charts have found widespread use in the concrete industry in both ready-mixed concrete and precast concrete sectors as a tool for quality control. Control charts can be a
24、pplied to monitor a range of product characteristics (e.g. cube/cylinder strength, consistence, w/c ratio), constituent materials (aggregate grading, cement strengths, etc.) or production (batching accuracy). Their most common application of control charts is as a means of continuously assessing com
25、pressive strength results in order to: check whether target strengths are being achieved; measure the variations from target (all products vary); identify magnitude of any variation; objectively define action required (e.g. change w/c ratio) to get the process back on target; identify periods and co
26、ncretes where the strength was less than specified so that investigations can be carried out and corrective action taken. The use of control charts should not be treated in isolation from the rest of production control. For example routine checking and maintenance of weigh equipment will minimise th
27、e risk of a weigh-scale failure. Control charts provide information about the process, but the interpretation of the information is not a mechanical process. All the information available to the concrete producer should be used to interpret the information and make informed decisions. Did a change i
28、n quality occur when a new batch of constituent was first used? Is all the family showing the same trend? Are other plants using similar materials showing a similar trend? Such information leads to the cause of the change in quality being identified and appropriate action being taken. For example a
29、loss of accuracy in the weigh-scales should lead to repair, maintenance and re-calibration and not a change in mix proportions. Where a change in mix proportions is required, the use of control charts can lead to objectively defined changes in proportions. Effective control of concrete production is
30、 more easily achieved when there are good relationships with the constituent material suppliers, particularly the suppliers of cementitious materials. Early warning of a change in performance from the constituent material supplier should be part of the supply agreement, e.g. that stock DIN CEN/TR 16
31、369 (DIN SPEC 18769):2014-04 CEN/TR 16369:2012 (E) 6 clinker is being used during the maintenance period, and on the basis of this warning, the producer will decide the appropriate action. Some producers use changes in cement chemistry to predict changes in concrete strength. Effective production co
32、ntrol is about using all this information to produce concrete conforming to its specification. Effective production control, which includes the use of control charts, significantly reduces the risk of non-conformity benefiting both users and producers of concrete. There are drawbacks to the existing
33、 method of assessment of conformity of mean strength adopted in EN 206-1 3 including not following the CEN Guidance on the evaluation of conformity 2. It is believed that control charts (already widely used as a quality assurance tool in factory production control) would provide an alternative and b
34、etter means of ensuring the characteristic strength is achieved and it is a method that follows the CEN Guidance. DIN CEN/TR 16369 (DIN SPEC 18769):2014-04 CEN/TR 16369:2012 (E) 7 1 Scope This Technical Report reviews various control systems that are currently used in the concrete industry and, by t
35、he use of examples, show how the principles are applied to control the production of concrete. This CEN/TR provides information and examples of the use of method C in Clause 8 of prEN 206:2012. 2 Symbols and abbreviations AOQ Average outgoing quality AOQL Average outgoing quality limit CmraConstant
36、giving the cement content increase required to produce a 1N/mm2increase in strength dc Change in cement content Dl Decision interval G Gradient fciIndividual test result for compressive strength of concrete fckSpecified characteristic compressive strength fcmMean compressive strength of concrete k S
37、tatistical constant LlLower limit LCL Lower control limit LWL Lower warning limit n Number of samples qnStatistical constant that depends upon n and the selected AOQL s Sample standard deviation UCL Upper control limit UWL Upper warning limit xiTest result NOTE According to EN 206-1 3, a test result
38、 may be the mean value of two or more specimens taken from one sample and tested at one age. x Mean value of n test results Estimate for the standard deviation of a population DIN CEN/TR 16369 (DIN SPEC 18769):2014-04 CEN/TR 16369:2012 (E) 8 3 Statistics for Concrete 3.1 Normal distribution of stren
39、gth Compressive strength test results tend to follow a normal distribution as illustrated in Figure 1. A normal distribution is defined by two parameters, the mean value of the distribution and the standard deviation ( ), which is the measure of the spread of results around the mean value. A low sta
40、ndard deviation means that most strength results will be close to the mean value; a high standard deviation means that the strength of significant proportions of the results will be well below (and above) the mean value. The area under the normal distribution between two values of x represents the p
41、robability that a result will fall within this range of values. The term tail is used to mean the area under the normal distribution between a value, e.g. a compressive strength, and where the frequency is effectively zero. For strength it is the lower tail, i.e. low strength results, that is import
42、ant but for other properties, e.g. consistence, both the lower and upper tails are important. Key X cube strength, N/mm Y frequency 1 target mean strength 2 specified Characteristic strength, fck3 minimum strength (fck 4) 4 tail Figure 1 Illustration of concrete strength distribution At the extremes
43、 of the strength range for a given set of constituent materials, the assumption of a normally distributed set of data may not be valid. It is not possible to have strengths less than zero and most concretes have a ceiling strength beyond which they cannot go. In these situations the data set is skew
44、ed. However as low strengths are of concern to specifiers, an assumption of normally distributed data does not lead to problems in practice. 3.2 Characteristic strength and target strength EN 206-1 3 specifies the characteristic compressive strength of concrete in terms of a standard cylinder test o
45、r a standard cube test carried out at 28 days. The characteristic strength is defined in EN 206-1 3 as the “value of strength below which 5 % of the population of all possible strength determinations of the volume of concrete under consideration, are expected to fall”. Put simply this means that if
46、every single batch was tested, 5 % of the results would fall within the lower tail of the normal distribution that starts 1,64 below the actual mean strength. However the actual mean strength will not be known until the concrete has been DIN CEN/TR 16369 (DIN SPEC 18769):2014-04 CEN/TR 16369:2012 (E
47、) 9 produced and tested and therefore the target mean strength (TMS) is usually set at some higher value to ensure the concrete achieves at least the specified characteristic strength. The target mean strength is given in Equation (1): TMS = fck+ k (1) where TMS = target mean strength fck= character
48、istic compressive strength = estimate for standard deviation of population k = statistical constant k = the margin The fixed point in the distribution is the specified characteristic strength and as the margin increases and/or the standard deviation increases, the target mean strength increases, see
49、 the following Example. EXAMPLE The target mean strength for a specified characteristic strength of C25/30 is given in Table 1. A standard deviation ( ) of 3 N/mm2is typical of a concrete with low variability and a value of 6 N/mm2represents high variability. Table 1 Target mean strength for specified characteristic strength of 30 N/mm2(cube) Margin Area in lower tail (i.e. percentage below charac
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