Sensor control of dry concrete mixes

First attempts to devise a reliable manufacturing control method for dry mix consistency proved inconclusive. However, this article from Czechoslovakia shows that a link was found between electric conductivity and the addition of water to the dry mix. This led to the deduction that the mix acts as an electrolyte in a galvanic cell; in turn this led to the design of an electrode probe sensor, which can be installed in the base of the mixer drum. Output voltage of the ‘cell’ as well as the current in one phase of the mixer drive motor can thus be monitored, the former providing the crucial measurement of mix consistency. Karel Hub works at the Institute of Railway Construction, Brno, and his co‐authors at the Research Institute for Mechanisation of Building Component Production, Prague.