A simulation computer program named RMCSIM has been developed to simulate a whole day of activities for a concrete plant with N mixing bays, M truckmixers (with two different capacities: 5 m and 7 m) serving S sites, where sites are at variable distances D from the plant and variable quantities Q are required by the sites in which different placing methods are used. It is developed based on a set of data which has been reported earlier in another paper (Anson et al., 2002). An optimal number of truckmixers for a particular day's order size can be found from the results of the simulations. The optimal volume of concrete that a truckmixer carries on any one day is found to be about 27 m in Hong Kong situations. It is also found that a two mixing bay concrete plant always provides better services than a one mixing bay plant. The mix combinations of 5 m and 7 m truckmixers in the fleet have no significant effect on concreting service performance. Lastly, it can be deduced that the causes of unsatisfactory concrete delivery performance are most likely due to site managers' difficulties in precise planning rather than the scheduling at the concrete plant. © 2005 Taylor & Francis Group Ltd.