Concept of “Efficient Coordination Zone” relating to truckmixer deliveries serving construction sites

Abstract

Matching the provision of concrete delivered by truckmixers to the needs of the crew placing concrete on site is difficult. In general, a placing crew spends some time idle, waiting for concrete to arrive on site, and yet, at other times, on the same pour, truckmixers form a queue waiting to be unloaded. The paper presents observations deriving from many pours of concrete in Hong Kong, of the amount of enforced waiting by the placing crew and the amount of enforced truckmixer waiting on site to be unloaded. The concept of an “efficient coordination zone” is introduced, for the industry to aspire to achieve, such that no placing crew would spend more than 10% of the duration of the pour in waiting for concrete and that truckmixer provision, in waiting on site and unloading, would not exceed 150% of the duration of the pour. A new model is introduced which estimates the performance of site and plant resources matching, in relation to the pour parameters of journey round trip time, RT, and the time needed to unload a truckmixer, UL. The model assumes a fleet of N truckmixers circulates between site and plant. The model may be of practical use in aiding truckmixer schedulers.