Measurement of the performance of ready mixed concreting resources as data for system simulation

Concrete is a very important construction industry material, and this is especially true in Hong Kong. The efficient organization of the supply of concrete from ready mixed concrete plants is beneficial to both concrete companies and contractors. It is also essential for an efficient construction industry, since a very high propor1 tion of the in situ concrete in Hong Kong is supplied ready mixed from an off-site plant. Whether concrete companies in Hong Kong are using their resources well and are able to satisfactorily match the timing of their deliveries to construction site needs are questions discussed in this paper, based on data collected by the authors. The data are planned for use in validating a simulation model of ready mixed concrete plant operations in Hong Kong. The third author spent 20 weeks in 1999-2000 at concrete batching plants in Hong Kong, studying their operations. Data on a sample of 15 typical operational days at four plants, which included 295 pours on sites and 1677 truckmixer trips, are presented. Truckmixer journey times for delivering concrete and journey times for returning to plants and their distributions have been found. Queuing statistics for truckmixers on site waiting to be unloaded, placing times when unloading concrete, washing out and waiting times on sites after unloading, and delays in the continuous delivery of concrete are also described. Service has been studied in terms of the matching achieved between site delivery timing require1 ments and the need to use truckmixers efficiently. For the 295 pours, the relationship is shown between gaps in the supply of concrete to site and the extent to which truckmixers are bunched in a queue on site. Matching was found to be good for only 17% of the 295 pours, the variability in service received by different sites is considerable, and the importance of studying the truckmixer scheduling problem is highlighted, so that this variability might be reduced and extreme cases eliminated.