Bs En 206 Pdf
Therefore, if the results contain a shift in the process mean at some point in time, all these deviations will be inflated and the sample standard deviation. If it fails this criterion, a more detailed investigation of the relationship is needed. Where possible, general recommendations are made.
Collaborate, Innovate, Accelerate. Application of the criteria to overlapping test results increases the risk of rejection. Due to the built-in margin, the fact that the calculated value exceeds the maximum value does not give rise to non-conformity.
The figures shown in bold are potentially non-conforming. The standard deviation used to calculate the Target Mean Strength and the position of the solid lines is that used for production control. Whilst a change in mean strength or standard deviation indicates a change in the conditions of production i.
The producer is free to select the membership of the family, but they have to be able to justify the selection and provide relationships to the Reference Concrete. Where the assessment period is defined in a different way, the last column of each table does not apply. It is recommended that a change in mean strength be not used to determine the end of a period of uniform production. With continual assessment of conformity, production can move from non-conformity to conformity and back to non- conformity. The use of non-overlapping results reduces the risk to the concrete producer and has the logic that each result is only considered once in the assessment of conformity.
Readymix concrete BS EN 206-1
It would be satisfactory for the producer to declare any proven non-conformity within a reasonable time after the end of each relevant assessment period. In practice the cost of sampling and testing concrete is such that only limited numbers of test results are available for conformity assessment. The number of specimens to be made from one sample is decided by the producer. However, certification bodies are likely to take the view that if the producer has evidence that the standard deviation has increased, el celoso extremeo pdf they should immediately adopt the new value for production.
Roberts showed that under typical United Kingdom conditions, test results are not auto-correlated. The Amendment has added to the number of clauses that refer to national provisions. Some special concretes that are outside of a family may never generate sufficient test data to take them into the conditions necessary for continuous production.
When this happens the steps in the solid and dashed lines coincide with the vertical grid lines. Only exceptional cases would warrant the introduction of additional limits. Check the production records for this batch. Where production data are plotted as a time series as in Figure B. Thus a change in the standard deviation should indicate the end of one assessment period and the start of the next.
As shown later, such concretes may require a higher margin than that needed with continuous production. This shows that the standard deviation calculated from the mean range has been less affected by the change in mean strength. However there may be practical problems with sampling at the plant with some production systems, particularly in respect of safety and obtaining a representative sample. Readers should note that Quarry Products Association publications are subject to revision from time to time and should therefore ensure that they are in possession of the latest version. There is also a general principle that non-conforming products should be prevented from reaching the market.
Conformity applies to conditions of uniform production. In this case, the data obtained prior to and after the short period of unstable conditions may be combined and assessed for conformity in the normal way. Marrion Jules Sequitin Mendoza. This new value of the standard deviation is applied to the next assessment period.
This may give a high level of auto-correlation of the test results and a low standard deviation. If there is a problem with a plant e. Where the check on relationships is combined with the conformity assessment, it may be used as a filter for the application of the confirmation criterion.
If a producer adopts a test rate such that this is a common occurrence, then his test results are likely to be auto-correlated. Conformity by the method of attributes is not applicable with this system. In practice, a series of at least test results should be used to calculate auto- correlations. It is assumed that they have some basic knowledge of statistics and that they can interpret and apply the information given in this publication to their particular situations.
In most cases this will not be the situation and the concrete will be required to be part of a family with additional conformity testing at the specified age. Unless there is a valid reason for rejecting the result, low outliers should be included in the conformity assessment but excluded from the check on standard deviation.
The two broken lines apply to the same circumstances as the first two, but when the test results are independent, not auto- correlated. For concrete having a specified strength requirement, every concrete family and every individual concrete i. The solid line shows the Target Mean Strength, calculated as the specified characteristic strength for the reference concrete plus two times the standard deviation. This can create a practical problem when the start of a new assessment period creates a period with less than the expected number of sets of compressive strength test results e.
BS EN 206 2013 A1 2016
The producer should have documentary evidence showing the effect on strength of these site additions of water. Prior to this the producer should be keeping a watch on the likelihood of achieving conformity and where this is in doubt, taking appropriate corrective measures. If these data are included, the individual criterion is not applicable. However such a method is not appropriate where the process average can change, as is the case with concrete production.
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