Determination of Soil Moisture Content

Moisture content measurement is mainly used to perform weight-volume calculations in soils. Also, moisture content is a measure of the shrink-swell and strength characteristics of cohesive soils.
Test applied: ASTM D2216: Standard Test Method for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass.
Equipment and Materials:

• Oven-safe containers
   
  *Disturbed sample of moist soil
   
  
  
   *Scale capable of measuring to the nearest 0.01 g
   
  *Soil drying oven set at 110^o ± 5 ^oC
  
  Procedure:
  Three measurements are taken in order to calculate the moisture content:
  1) Mass of container, M_c;
  2) mass of moist soil plus container before drying, M₁; and
  3) mass of dry soil plus container after drying, M₂.
  Moist soil is placed in an oven-safe container and dried for 12-16 hours in a soil drying oven. The soil-filled container is weighed before and after drying to obtain M1 and M2, respectively.
  The moisture content, w is calculated as the mass of water in the soil, M_w divided by the sum of the mass of soil solids, M_s
  
  Precautions: 
  
• Avoid inadequate drying, or excessive drying beyond the recommended 12-16 hour drying period.
• For soils containing a significant amount of organic material or hydrous minerals such as gypsum, the oven temperature should be reduced to 60 ^oC instead of 110 ^oC as in these cases, some of the water is bound by the soil solids, so excessive drying will effectively drive some of the soil solids away and produce erroneous results.