Moisture Measurement in Concrete Production

Hydronix sensors were originally designed for moisture measurement in concrete production and are built to survive the harsh environment of flowing aggregates and the turbulence of a concrete mixer. Manufacturers are required to produce quality concrete to rigorous specifications, batch after batch while keeping costs to a minimum. Hydronix sensors can be used to control the moisture content of every batch to within +/- 0.1% moisture.

Benefits

• Consistent batch quality
• Consistent batch sizes
• Alarm function for high or low moisture contents
• Reduction in cement use
• Reduction in wastage due to incorrect moisture or slump
• Reduced mix cycle times

One of the major causes of inconsistency in batching concrete is the varying moisture content of the sand and aggregates from one batch to another. Good storage of the sand and aggregates can help, but even for materials stored in covered silos the moisture will be constantly changing due the inevitable effects of drainage. Moisture content in stored sand and aggregates can have dramatic effects on the water/cement ratio, the aggregate/cement ratio, yield and the colour of the mix. Measuring the moisture content of the raw materials can enable the plant controller to adjust water addition into the mix in real time, minimising these effects. This enables batch after batch of concrete to be produced to the same, consistent quality.

The installation of moisture measurement sensors into the manufacturing process provides the producer with an on-line system that operates in real time and enables the accurate control of the water/cement or aggregate/cement ratios. Knowing the moisture levels of the raw materials allows the producer to accurately calculate not only the amount of water to be added to the mix but also the correct amount of cement and aggregates. This will reduce costs and also the level of rejected batches.

Hydronix microwave moisture measurement sensors can be installed in a variety of locations depending upon the individual requirements of the plant. The Hydro-Probe can be installed either in the neck of an aggregate bin or underneath the bin gate and measures moisture as the raw material passes over the sensor. Alternatively it could be mounted above a conveyor belt and measure the moisture in the aggregate as it flows past the sensor face plate. The Hydro-Mix moisture sensor has been designed to fit level with the floor of a concrete mixer and can be installed in pan mixers, planetary mixers and single and twin shaft mixers. Alternatively, the Hydro-Probe Orbiter can be mounted to the scraper arm of a pan or turbo mixer or the side of a rotating pan mixer and measures moisture content directly in the mix. All sensors connect directly to the plant control system using an analogue output or digital connection. For optimum accuracy the mixer sensors will also connect to the Hydronix water control system, the Hydro-Control VI, allowing precise control of water addition into the mix. This may be retro fitted or installed as a stand-alone unit.