Trade Journals for the Concrete Industry

Ready-mix concrete that travels long distances in the truck mixer frequently exhibits a different consistency on arrival at the building site to that at the time of filling. The slump, which is taken as an evaluation criterion for the determination of the consistency class during the acceptance test, can deviate in extreme cases by up to 90 mm. After all, that corresponds to one and a half consistency classes. The precise change in the consistency during the journey depends on the duration of the journey, the stress in the truck mixer as well as the concrete recipe used and is not reliably predictable before filling into the real truck mixer. In order to investigate the interrelationships between concrete transport and changes in the properties of the mixture, the IAB - Institut für Angewandte Bauforschung Weimar gGmbH [Institute of Applied Building Research Weimar Ltd] (IAB) and Testing Bluhm & Feuerherdt GmbH (Testing) have developed a truck mixer simulator on a laboratory scale that can simulate the stress to which the fresh concrete is subjected in a real truck mixer and offers the possibility to determine the associated changes in consistency.