Concrete mixing experiments have been carried out at an industrial batching plant during a typical production day. 34 batches were tested, including a number of water-to-powder mass ratios, paste contents and mixer filling ratios. Three "in-mixer" measurements yield critical information about mixture composition: mixing power, Orbiter - a revolving microwave sensor, and Viscoprobe (TM) - a drag force measurement on a ball-shaped probe moving through the mixture. A model of the microstructural state evolution in concrete components vs. mixing time is proposed herein. The transient mixture states are associated with different power dissipation levels (frictional, cohesive or viscous) and apparent density characteristics. it will be shown that the three sensors are also able to indicate the evolution of mixture state during mixing, thus facilitating comprehension of sensor signal variations during the mixing cycle, in addition, a method is devised to improve sensor measurement of the water-to-powder ratio by up to three times. More specifically, the precision of the measured water-to-powder mass ratio is 0.0035, 0.0042 and 0.0051 using the Viscoprobe (TM), Orbiter and mixing power techniques, respectively. The typical water-to-powder mass ratio values for concrete range between 0.4 and 0.6. (C) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.