Concrete placing crew and truckmixer productivities as affected by delivery scheduling policies

Abstract

When ready mixed concrete is placed in forms on site, the goal is to ensure that both the placing crew is never idle when waiting for a delivery of concrete and that concrete delivery truckmixers never have to wait in a queue to be unloaded. This situation is almost never achieved in practice for a routine pour. Usually, both crews and truckmixers have to wait for some of the time. To better understand the behavioural characteristics of the concreting system, in terms of crew idle time and truckmixer excess time on site, simulation experiments were carried out to compare the effects of two truckmixer plant dispatch policies. For larger pours in particular, a serial dispatch policy is found more wasteful of truckmixer time than circulating dispatch as long as the correct size of circulating fleet is chosen. In addition, for serial dispatch, due to the system flow parameter variabilities seen in real life, it is suggested that to choose the theoretically optimum dispatch interval at the plant is wasteful of truckmixer time and that better coordinated plant and site resource matching requires slightly greater choice over the length of intervals.