Advanced online water content measurement for self-compacting concrete production in ready-mixed concrete plants

Abstract

In ready-mixed concrete plants, the water content of self-compacting concrete (SCC) is generally controlled during the mixing process based on the stabilisation of mixer power consumption. This measurement system is however rarely calibrated, even though its signal is sensitive to the wear of mixers and the temperature of engines.The aim of this paper is to propose a calibration of mixing power as a measurement of the concrete water content that enables improving water control accuracy. A new approach based on the mixing power evolution is devised for a better determination of the signal stabilisation. The stabilisation time is then defined and considered as the necessary mixing time of each concrete batch. Experimental results obtained from 40 batches of different SCC compositions produced in a full-scale concrete plant have shown that, with the developed calibration method, the stabilisation of power consumption can be considered as a reliable indication of water content with a precision of ±3.8l/m3. It is also observed that the water-to-powder ratio (W/P) and the use of viscosity agent have significant effects on the power consumption evolution during mixing.