C-13: Computerized Concrete QC Using Spreadsheets and Cusum Graphs


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Title: C-13: Computerized Concrete QC Using Spreadsheets and Cusum Graphs

Author(s): Ken W. Day

Publication: Technical Documents



Appears on pages(s): 48


Date: 1/1/1991


Note: C-13 is Out of Print. However, a PDF version is available.

These articles were written largely during 1987 and so are no longer the latest versions of the system described. However, they are still relevant today because they were not intended to provide readers with a ready-made system to copy and use as it stood. Rather, the purpose was threefold. One objective was to assist the non-computer-literate reader to learn to use Lotus 123. A second was to present new techniques of quality control and the third was to show how Lotus could be used to implement these techniques. It is likely that large numbers of ACI members will be freshly embarking on the use of computer spreadsheets for years to come. It is certain that the "new techniques" of QC, while now more developed and more solidly established, have yet to spread outside the most innovative 1% of the concrete industry. They are no longer new to leading theorists but they are yet to come to the serious attention of the majority of potential users. If an individual wishes to learn from scratch how to use a computer and to go on to develop their own QC system, these articles should at least halve the time and effort involved. It is of course possible that the newly reinvented wheel will be a better wheel, or will at least fit better into its appointed place, but it should be realized that its cost (of several thousand hours for a complete system) will not be competitive with the purchase of a ready-made system. This publication is therefore commended to the readers as a textbook on the use of Lotus 123 and on available techniques of concrete quality control. The first few articles will enable the rapid production of an elementary control system which is at least more effective than most of those in current use. The implementation of the more sophisticated techniques in the later articles is better handled by a compiled program (the author uses Borland "Turbo C"). Such a program runs very much faster and is much more bullet-proof and easily learned. However, it does not show its workings to the user and so is less educational. The latest trends in concrete QC/QA appear to be for it to be largely left in the hands of the producer but with de- tailed reporting, availability of data and incorporation of a small proportion of independent duplicated tests so that users can assure themselves at minimal cost that the concrete is under effective control. The situation has been completely transformed by the availability of computer batching systems which accurately report the actual as-batched quantity of every ingredient of every truckload. While such data has been available as a print-out for over a decade now, what is new are systems which make efficient use of it. This has very significant implications on the necessary sampling rate for conventional testing because it is now known to what extent each sample is truly representative of the whole spectrum of concrete produced. In effect, the strength of the (unsampled) weakest truckload of concrete produced can be calculated. A further transformation is wrought by bringing Forward the age at which strength is measured to 24 hours or less without the use of conventional accelerated curing and by extending this technique to the determination of in-situ concrete strength. The technological basis of all these developments is presented in this series of articles but their actual implementation in computer programs has been developed substantially since their publication.