Water content has traditionally been expressed as the dimensionless ratio of the mass of water present in the sample to the mass of the sample after it has been dried to a constant weight (dry-weight-basis). A relation to the mass of the wet sample (wet-weight-basis) is also very common. Multiplied by 100 these ratios become percentages by weight.

But numerous other definitions exist, for example as "relative" moisture in percentages of saturation, or as "equilibrium" moisture depending on the relative humidity of the surrounding air, and, last but not least, the relationship between the "volume" of water present in the total volume of the sample in percentages by volume.

To avoid confusion it is advisable to not only give the plain number of the moisture but also the basic definition used (e.g. 10% by volume).

Physical principles render the TRIME-system subject to the „volumetric" moisture definition. If the measure of moisture in % by weight is desired, the values must be divided by the known dry- or wet-bulk-density of the material.

 

Definition of Gravimetric Moisture



with = gravimetric moisture on a dry mass basis in % by weight
= mass of water present in the sample
= dry mass of the sample

 



with = gravimetric moisture on a wet mass basis in % by weight
= mass of water present in the sample
= wet or total mass of the sample

 

Definition of the Volumetric Moisture



with = volumetric moisture of sample in % by volume
= volume of water inside the sample
= total volume of sample

 

Definition of Dry Density

The dry density describes the relationship between the dry mass and the total volume of the sample:



 

Definition of Wet Density

The wet density describes the relationship between the wet or total mass and the total volume of the sample:



 

Relationship between Gravimetric and Volumetric Moisture

The relationship between gravimetric and volumetric moisture is as follows:



respectively



with = gravimetric moisture in % by weight (dry- / wet-weight basis).
= dry density of sample
= wet density of sample
= density of water (» 1)

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