Sensors for all aggregates

Moisture sensor technology improves concrete quality

Fig. 1 Moisture sensor Sono-Vario measures 16 mm gravel at the silo discharge with long-term stability.

Fig. 2 Control software indicates the moisture value of the various aggregates in the yellow box.

Fig. 5 Owing to the new geometry of the sensor with the waveguide furnished at the surface, wear and tear of the sensor have no effect on the measuring value.

In times of ever increasing demands in terms of quality when manufacturing and processing concrete it is a matter of fact that the sensor technology for moisture measurement is faced with ever growing demands too. Nowadays, it is not only necessary to use a precise measuring technique but to direct even more attention to calibration, startup and process-related disturbance variables too.

Moisture measurement of the various aggregates

Normally just the moisture of the aggregate sand is measured if moisture measurement is carried out at all. But, if you look at the moisture distribution in all aggregates (Table 1), it becomes clear that only measuring the sand moisture provides an improper indication about the actual total water content.

If, however, a plant is operating with the moisture measurement of the sand and firmly set values for the gravel aggregates, then in most cases the plant is running with a tolerance of about ±10 liters. This means that either attention has to be...