Measuring Viscosity of Fresh Concrete by Sensing Torque - Case Study

Measuring Torque to Control Concrete Viscosity

Background

Torque Measurement is a very simple mechanical process; in essence, it is a measure of the ‘force’ used in turning (or attempting to turn) something. When a force or ‘torque’ is applied to a shaft, the shaft twists (by a very small amount). This twisting produces a ‘stretch’ in the material of the shaft, and it is this process that allows a measurement of force in the mixing process. The input torque applied to a mixer is directly related to the measuring viscosity of the mixture.

Our client needed to apply these principles to a large-scale concrete production at Terminal 5 Heathrow. The existing system used the measurement of the electrical input power (KW) to determine the viscosity of the mix. Large fluctuations in the input voltage and the inherent inaccuracies of measuring power on large motors, in this way, made control of the process difficult. The ability to control and monitor the quality of concrete produced was being disrupted due to the inconsistency of power being supplied. Therefore, a more reliable measurement of the mix viscosity was required.