Fly Ash Moisture


Maintaining the necessary correct fly ash moisture levels has become a critical component during processing. The MoistTech sensor will monitor the fly ash process in both wet and dry applications to reduce dust and to provide dryer control. As an embankment or fill material, fly ash is used as a substitute for natural soils. Fly ash in this application must be stockpiled and conditioned to its optimum moisture content to ensure that the material is not too dry and dusty or too wet and unmanageable. When fly ash is at or near its optimum moisture content, it can be compacted to its maximum density and will perform in an equivalent manner to well-compacted soil.

The water content of the fly ash stabilized soil mixture affects the strength. The maximum strength realized in soil-fly ash mixtures generally occurs at moisture contents below optimum moisture content for density. For silt and clay soils the optimum moisture content for strength is generally four to eight percent below optimum for maximum density. For granular soils the optimum moisture content for maximum strength is generally one to three percent below optimum moisture for density. Therefore, it is crucial that moisture content be controlled during construction. 

In the presence of moisture, fly ash reacts with lime at ordinary temperature and forms a compound possessing cement like properties. After reactions between lime and fly ash, calcium silicate hydrates are produced which are responsible for the high strength of the compound.
Conditioned: In this method, water is added to the fly ash to facilitate compaction and handling. The amount of water added being determined by the end use of the fly ash. Conditioned fly ash is widely used in aerated concrete blocks, grout and specialist fill applications.


Installing the CCS3000 fly ash moisture sensor directly over the material being conveyed allows any manufacturer can continuously monitor the process. In addition, MoistTech’s state-of-the-art sensor can control the fly ash moisture content instantly, either manually or automatically.


Dust from the product is not normally a problem. However, in extreme dusty environments, we recommend the installation of an Air Purge System to prevent the accumulation of material on the sensor’s window.

Benefits of Fly Ash Moisture Detection

  • Improved Product Quality
  • Lower Energy Costs
  • Reduced Start-up Times
  • Less Waste
  • 100% Product Inspection
  • Less Down time

The MoistTech staff is very experienced with the requirements in the production of fly ash. Our sensor calibrations, measurement wavelengths, algorithms and sensor optical requirements are pre-set at the factory. Typical accuracy is about ±0.1% moisture. Typical analog range is 0-10% moisture and up to as much as 40%, subject to application. The outputs can be adjusted to optimize PLC or recording requirements.

Take a look at our other chemical moisture measurement applications.