Design and application of risk-adjusted cumulative sum for strength monitoring of ready mixed concrete

Abstract

The cumulative sum procedure is an effective statistical process control tool that can be used to monitor the quality of ready mixed concrete during its production process. In this paper, an attempt has been made to design and apply a new cumulative sum procedure for the ready mixed concrete industry, which takes care of the risks involved in and associated with the production of concrete. This new procedure can be termed as risk adjusted cumulative sum. The 28-day characteristic cube compressive strengths of the various grades of concrete and detailed information regarding the production process and the risks associated with production were collected from the operational ready mixed concrete plants in and around Ahmedabad and Delhi, two important cities in India. The risks were quantified using a likelihood-based scoring method. Finally, a risk adjusted cumulative sum model was developed by imposing the weighted score of the estimated risks on the conventional cumulative sum plot. This model is a more effective and realistic tool for monitoring the strength of ready mixed concrete.