Design and application of multivariate CUSUM for quality monitoring of ready mixed concrete

Multivariate CUSUM control charts provide a unified scheme to monitor process mean and variability when there are multiple processes that need to be monitored to track the problem causing a change in the quality characteristic of the process. This paper aims at developing a set of multivariate CUSUM control charts for monitoring the quality of ready mixed concrete. On analysing available grades of concrete produced by two commercial batching plants in Ahmedabad, India, it has been observed that after application of multivariate CUSUM control charts along with V mask, if the identified point is the same for three or more quality characteristic then definitely there is a strong indication about occurrence of a problem at that point. The root cause investigation at the identified point would reveal the cause of the change in strength. The remedial action would be to modify the mix design and improve the quality of materials and workmanship.