Concrete mixing kinetics by means of power measurement

This paper introduces a new model for concrete mixing kinetics. The model defines five successive stages through which the mixture characteristics change. It is also shown that the time-variation of the mixer power consumption is a relevant tool to identify the transient stages of the mixture during mixing. In particular. it detects the instant when maximum cohesive paste occurs and identifies the fluidity time. The fluidity time is the instant when mixture turns to fresh concrete. In that sense, this transition time can be seen as an indicator of mixing difficulty fora given mixer. The influence of the mix-design and that of the liquid loading sequence on the mixing behavior are investigated; three sets of experiments are used for the assessment of the model. It is shown that one key parameter is the rheology of the mixture at the fluidity time. (C) 2008 Elsevier Ltd. All rights reserved.