At the WIB (Werkstoff im Bauwesen = Building Industry Materials) section of the Institute of Structural Concrete at the TU Darmstadt, plant and process-specific developments are ongoing with a view to adapting and expanding existing mixing plants to the requirements of the mixing task so that even the demanding mixtures for SCC, HPC and UHPC can be manufactured reliably with a retrofitted standard mixing plant. In the following article, the particular demands placed on the mixing process by mixture compositions that are rich in fines but with a low water content will be explained, and various innovative methods in terms of plant and process technology will be shown with which fines can be optimally solubilised and the entire mixture fully homogenised with a minimised mixing duration. To this end a pilot mixing plant with two different mixing systems was constructed in the research laboratory at the TUD. Hence, a conventional twin-shaft mixing system on the one hand and a conical mixing system on the other were procured. The laboratory was supplemented by a colloidal mixing system in order to accomplish particularly energy-intensive mixing processes. All appliances at the WIB were equipped with the latest generation of frequency converters and particularly powerful drive motors in order to be able to manufacture the very demanding concretes in an optimum manner. The technology which is henceforth available in the mixing laboratory is used to analyse in detail the demands on the mixing process and to develop suitable mixing regimes for the problems specific to concrete. The aim is to transfer the findings obtained in the mixing laboratory over to large mixing plants.
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