Chapter 13 Optimisation; Mixer; Ingredients - Hydronix Hydro-Control VI Operator's Manual

Chapter 13
The moisture reading from a sensor can only indicate what is happening in your mixer. The speed of
reading, or the time taken to reach a steady reading when the materials are homogeneous, reflects the
effectiveness of the mixer. By taking some simple precautions the overall performance can be
considerably improved and the cycle time reduced with consequent financial savings.

1 Mixer

Mixers vary in performance, a well maintained mixer will always be more efficient than a
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poorly maintained mixer.
Look at the mixing process. Check how the water disperses. If water sits on top of the
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aggregates for a time before dispersing, then spray bars will be required to disperse the
water into the mixer more quickly to shorten the mixing time.
Spray bars are more effective than single water inlets. The wider the area the water sprays,
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the faster it will mix into the material.
Add water during the aggregate addition.
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Keep the mixer blades adjusted to 0-2mm above the mixer floor. This will have the
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following benefits:
All the residual mix is discharged when emptying the mixer.
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The mixing action close to the floor of the mixer is improved, thereby improving the
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reading of the sensor.
• Wear on the mixer floor plates will be reduced.
• Reduced cycle times will result in savings in power consumption and reduce mixer wear.

2 Ingredients

If the aggregate masses are not corrected for high moisture contents, then the
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aggregate/cement ratio will change considerably, having an adverse effect on consistency
and concrete performance. There will also be varying ratios of the different aggregates
used and this can increase the amount of water to achieve the repeatable consistency
If the aggregates are very wet, as may be the case at the beginning of the day due to water
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draining in the storage bin then there may be more water in the aggregates than the mix
requires.
The moisture content of the aggregates should be above the saturated surface dry (SSD).
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Hot cement can affect consistency (workability) and thus water demand.
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• Changes in ambient temperature can affect water demand.
• Where possible, the cement should be added either at the same time or within a few
seconds after the start of the addition of sand and aggregates. Combining the materials
together in this way will greatly assist the mixing process.
Hydro-Control VI Operators Guide HD0456 Rev 1.7.1
Optimisation
73