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Moisture and Density (MAD)

Overview

Thumbnail image of moisture and density Mineral density, porosity, void ratio, and water content are basic sediment/soil and rock properties that are found most accurately through mass and volume determinations.

Moisture and density (MAD) data provide a direct estimate of porosity and void ratio and the average density of constituent minerals. Porosity variations are controlled by consolidation and lithification, composition, alteration, and deformation of the sediments/soils or rocks. MAD data can be used to calibrate high-resolution bulk density data collected on the Whole-Round Multisensor Core Logger (WRMSL).

Instrument Make and Model

Custom-built system.

Estimated Measurement Time

  • Sample Preparation: ~1 day
  • Sample Measurement: ~15 samples/hour

Quantity of Sample Material

5–20 grams per sample

Principles & Analytical Capabilities

For MAD measurements, the mass or volume of the bulk (wet) material, the dried material, and the extracted water (assumed to be interstitial pore fluid) is corrected for the mass and volume of salt evaporated during the drying process. The mass and volume of the evaporated pore water salts are calculated for standard seawater salinity, seawater density at laboratory conditions, and an average seawater salt density. Soils can be either 2-phase or 3-phase compositions (i.e., completely dry or partially saturated).

For MAD measurements it must be determined whether the sample contains a 2- or 3-phase system:

  • Completely dry soil contains 2 phases: solid soil particles and pore air.
  • Fully saturated soil also contains 2 phases: solid soil particles and pore water.
  • Partially saturated soil contains 3 phases: solid soil particles, pore water, and pore air.

Moisture and density measurements are generally made using one of two methods. For sediment samples, wet mass, dry mass, and dry volume are measured using the helium pycnometer. Samples are extruded into a pre-weighed sample vial, measured by balance for wet mass, and are then dried at 105℃ for 24 hours. Samples are subsequently cooled in a dessicator before weighing their dry mass followed by dry volume measurement in the helium pycnometer.

For samples that are highly porous and do not retain water at a controllable saturation point (e.g., coral) wet (bulk) volume is determined by measurement of physical dimensions (e.g., a caliper measuring the sides of a cube or the diameter and length of a cylinder). Dry mass and dry volume are measured using the helium pycnometer.

The GCR helium pycnometer has six independent cells that can be utilized simultaneously. Typically, a standard consisting of a known volume of high-precision ball bearings is run in one cell and five samples are measured in the other six cells. Each measurement defaults to three replicates of helium expansion and includes a number of helium purge steps to drive out air and try to achieve an ideal gas inside the cells for the purposes of volume determination.

Data Generated

Data components:

  • Wet mass (g): mass of the sample, including the mass of the pore water, solid material, and dissolved salt.
  • Dry mass (g): mass of the dried sample, including evaporated salt.
  • Wet volume (g/cm3): includes volume of porewater, sample, and dissolved salt.
  • Dry volume (g/cm3): includes the volume of sample and evaporated salt.
  • Pore water mass (g): mass of the pore water in the sample.
  • Pore water volume (g/cm3): volume of the pore water in the sample.
  • Mass of solids (g): mass of the solids in the sample, with salt excluded.
  • Mass of salt (g): mass of the salt in the sample.
  • Volume of salt (g/cm3): mass of the salt in the sample.
  • Wet moisture content (wt %): relative moisture content of the sample, expressed in percentage on a weight of water/weight of bulk sample (including moisture and dissolved salt) basis.
  • Dry moisture content (wt %): relative moisture content of the sample expressed in percentage on a weight of water/weight of dry sample (without evaporated salt) basis.
  • Calculated bulk density (g/cm3): grams of mass per cubic centimeter of volume of the bulk sample.
  • Density of solids/grain density (g/cm3): grams of mass of solids without the mass of evaporated salt per cubic centimeter of solids, excluding the volume of evaporated salt.
  • Dry density (g/cm3): grams of mass of solids, including mass of evaporated salt, per cubic centimeter of bulk sample.
  • Porosity (vol %): volume of pore water per volume of bulk sample expressed in percent.
  • Void ratio (unitless): ratio of the volume of pore water per volume of solids, without the volume of the evaporated salt.

Data files:

  • Compiled results (CSV): tabular file of discrete measurements.

Data Example

Graph of bulk density, porosity, and grain density of moisture and density (MAD) measurements from Hole U1609A.
Bulk density, porosity, and grain density of moisture and density (MAD) measurements from Hole U1609A of IODP Expedition 401 on the continental slope of the Portuguese margin.1

Procedures & Manuals

References

1  Flecker, R., Ducassou, E., Williams, T., Amarathunga, U., Balestra, B., Berke, M. A., Blättler, C. L., Chin, S., Das, M., Egawa, K., Fabregas, N., Feakins, S. J., George, S. C., Hernández-Molina, F. J., Krijgsman, W., Li, Z., Liu, J., Noto, D., Raad, F., … Yousfi, M. Z. (2025). IODP Expedition 401 Moisture and Density [Data set]. International Ocean Discovery Program. https://doi.org/10.5281/zenodo.16458355