Process monitoring of RMC by application of EWMA control charts

Abstract Exponentially Weighted Moving Average (EWMA) control charts are one of the latest development in hybrid control charts developed for Six-Sigma Quality Control. These charts have a wide variety of applications and one of it is in process monitoring. Ready Mixed Concrete industry in India still follows very basic quality control tools of taking out mean and standard deviation. These statistical tools do not monitor the whole manufacturing process. This results in highly inconsistent quality which may not be reliable. It was realized that the standard deviation was not very high, but still the strength for the same grade of concrete was highly unpredictable. It was observed that concrete produced at the commercial RMC plants had a very high amount of design margin to secure the strength criteria against all the unanticipated constraints. This paper is an attempt to develop EWMA control chart for monitoring the process and quality of concrete, primarily in terms of its compressive strength. The results have proven to be useful in terms of detecting the small shifts from the targeted mean strength. Application of EWMA charts can bring a good amount of cement saving. These control charts can be recommended to Ready-Mixed-Concrete producers to achieve consistency in strength monitoring and also in achieving optimized cost.