CEN/TR 16369:2012
(Main)Use of control charts in the production of concrete
Use of control charts in the production of concrete
This Technical Report reviews various control systems that are currently used in the concrete industry and, by the 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.
Anwendung von Qualitätsregelkarten bei der Herstellung von Beton
Utilisation des cartes de contrôle pour la production du béton
Uporaba kontrolnih kart kontrole kakovosti pri proizvodnji betona
To tehnično poročilo zajema pregled različnih kontrolnih sistemov, ki se trenutno uporabljajo v betonski industriji, in z uporabo primerov prikazuje, kako se načela uporabljajo za kontrolo proizvodnje betona. Ta standard CEN/TR podaja informacije in primere uporabe metode C iz točke 8 standarda prEN 206:2012.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-februar-2013
Uporaba kontrolnih kart kontrole kakovosti pri proizvodnji betona
Use of control charts in the production of concrete
Anwendung von Qualitätsregelkarten bei der Herstellung von Beton
Utilisation des chartes de contrôle pour la production du béton
Ta slovenski standard je istoveten z: CEN/TR 16369:2012
ICS:
03.120.30 8SRUDEDVWDWLVWLþQLKPHWRG Application of statistical
methods
91.100.30 Beton in betonski izdelki Concrete and concrete
products
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
TECHNICAL REPORT
CEN/TR 16369
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
October 2012
ICS 91.100.30; 03.120.30
English Version
Use of control charts in the production of concrete
Utilisation des cartes de contrôle pour la production du Anwendung von Qualitätsregelkarten bei der Herstellung
béton von Beton
This Technical Report was approved by CEN on 20 May 2012. It 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, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2012 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 16369:2012: E
worldwide for CEN national Members.
Contents Page
Foreword .4
Introduction .5
1 Scope .7
2 Symbols and abbreviations .7
3 Statistics for Concrete .8
3.1 Normal distribution of strength .8
3.2 Characteristic strength and target strength .8
3.3 Standard deviation. 10
3.4 Setting the target strength . 13
4 Simple Data Charts . 14
5 Shewhart Charts . 15
5.1 Introduction . 15
5.2 Shewhart action criteria . 16
5.2.1 Points beyond UCL or LCL . 16
5.2.2 Points beyond UWL or LWL . 16
5.2.3 Patterns within control limits . 16
5.3 Control of standard deviation . 16
5.4 Example Shewhart chart . 16
5.5 Modified application of Shewhart control chart . 17
6 CUSUM . 19
6.1 Introduction . 19
6.2 Controlling mean strength . 22
6.3 Controlling standard deviation . 22
6.4 Controlling correlation . 23
6.5 Design of V-mask . 24
6.6 Action following change . 24
7 Multivariable and Multigrade Analysis . 26
7.1 General . 26
7.2 Multivariable . 26
7.3 Multigrade . 27
8 Speeding the Response of the System . 28
8.1 Early age testing . 28
8.2 Family of mixes concept . 28
9 Guidance on Control Systems . 30
9.1 Abnormal Results . 30
9.2 Handling mixes outside the concrete family . 30
9.3 Handling mixes not controlled by compressive strength requirements . 31
9.4 Test rates . 32
9.5 Action following change . 33
10 EN 206-1 Conformity Rules for Compressive Strength . 33
10.1 Basic requirements for conformity of compressive strength . 33
10.2 Assessment period . 34
10.3 Conformity rules for compressive strength . 34
10.4 Achieving an AOQL of 5 % with CUSUM . 36
10.5 Non-conformity . 37
11 Implementing Control Systems . 38
12 CUSUM Example . 38
12.1 Reference mix and concrete family . 38
12.2 Main relationship . 39
12.3 Applying adjustments . 40
12.4 CUSUM calculation . 41
12.5 CUSUM action following change . 45
12.6 Further data and a change in standard deviation . 47
Bibliography . 51
Foreword
This document (CEN/TR 16369:2012) has been 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 any or all such patent rights.
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 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 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 causes, but any variation outside of these limits, special variations,
would represent a change in the underlying process.
Shewhart’s 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 specified 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 changed 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 applied 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 compressive
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 concretes 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 the 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 in 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 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 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
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 cem
...
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