In
materials science
Materials science is an interdisciplinary field of researching and discovering materials. Materials engineering is an engineering field of finding uses for materials in other fields and industries.
The intellectual origins of materials sci ...
, bulk density, also called apparent density, is a
material property
A material property is an intensive property of a material, i.e., a physical property or chemical property that does not depend on the amount of the material. These quantitative properties may be used as a metric by which the benefits of one ma ...
defined as the
mass
Mass is an Intrinsic and extrinsic properties, intrinsic property of a physical body, body. It was traditionally believed to be related to the physical quantity, quantity of matter in a body, until the discovery of the atom and particle physi ...
of the many particles of the material divided by the bulk volume. Bulk volume is defined as the total
volume
Volume is a measure of regions in three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch) ...
the particles occupy, including particle's own volume, inter-particle
void volume, and the particles' internal
pore
Pore may refer to:
Biology Animal biology and microbiology
* Sweat pore, an anatomical structure of the skin of humans (and other mammals) used for secretion of sweat
* Hair follicle, an anatomical structure of the skin of humans (and other ...
volume.
Bulk density is useful for materials such as
powder
A powder is a dry solid composed of many very fine particles that may flow freely when shaken or tilted. Powders are a special sub-class of granular materials, although the terms ''powder'' and ''granular'' are sometimes used to distinguish se ...
s,
granules, and other "divided"
solid
Solid is a state of matter where molecules are closely packed and can not slide past each other. Solids resist compression, expansion, or external forces that would alter its shape, with the degree to which they are resisted dependent upon the ...
s, especially used in reference to
mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...
components (
soil
Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...
,
gravel
Gravel () is a loose aggregation of rock fragments. Gravel occurs naturally on Earth as a result of sedimentation, sedimentary and erosion, erosive geological processes; it is also produced in large quantities commercially as crushed stone.
Gr ...
),
chemical substance
A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. Chemical substances may take the form of a single element or chemical compounds. If two or more chemical substances can be com ...
s,
pharmaceutical
Medication (also called medicament, medicine, pharmaceutical drug, medicinal product, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy ( pharmacotherapy) is an important part of the ...
ingredient
In a general sense, an ingredient is a substance which forms part of a mixture. In cooking, recipes specify which ingredients are used to prepare a dish, and the term may also refer to a specific food item in relation to its use in different re ...
s, foodstuff, or any other masses of corpuscular or
particulate matter
Particulate matter (PM) or particulates are microscopic particles of solid or liquid matter suspended in the air. An ''aerosol'' is a mixture of particulates and air, as opposed to the particulate matter alone, though it is sometimes defin ...
(
particles
In the physical sciences, a particle (or corpuscle in older texts) is a small localized object which can be described by several physical or chemical properties, such as volume, density, or mass.
They vary greatly in size or quantity, from s ...
).
Bulk density is not the same as the
''particle density'', which is an
intrinsic property of the solid and does not include the volume for voids between particles (see:
density of non-compact materials).
Bulk density is an
extrinsic property of a material; it can change depending on how the material is handled. For example, a powder poured into a cylinder will have a particular bulk density; if the cylinder is disturbed, the powder particles will move and usually settle closer together, resulting in a higher bulk density. For this reason, the bulk density of powders is usually reported both as "freely settled" (or "poured" density) and "tapped" density (where the tapped density refers to the bulk density of the powder after a specified compaction process, usually involving vibration of the container.)
Soil
The bulk density of soil depends greatly on the mineral make up of soil and the degree of
compaction. The density of
quartz
Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...
is around but the (dry) bulk density of a mineral soil is normally about half that density, between . In contrast, soils rich in soil organic carbon and some friable clays tend to have lower bulk densities () due to a combination of the low-density of the organic materials themselves and increased
porosity
Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...
. For instance, peat soils have bulk densities from . In a detailed study which has used 6,000 analysed samples in the European Union, a high resolution map (100m) of soil bulk density for the 0-20cm using regression model. Croplands have almost 1.5 times higher bulk density compared to woodlands.
Bulk density of soil is usually determined from a
core sample
A core sample is a cylindrical section of (usually) a naturally-occurring substance. Most core samples are obtained by drilling with special drills into the substance, such as sediment or rock, with a hollow steel tube, called a core drill. The ...
which is taken by driving a metal corer into the soil at the desired depth and horizon. This gives a soil sample of known total volume, . From this sample the wet bulk density and the dry bulk density can be determined.
[Argonne National La]
"RESRAD Data collection handbook, chapter 2 -- Soil density" retrieved May 26, 2012
For the wet bulk density (total bulk density) this sample is weighed, giving the mass . For the dry bulk density, the sample is oven dried and weighed, giving the mass of soil solids, . The relationship between these two masses is , where is the mass of substances lost on oven drying (often, mostly water). The dry and wet bulk densities are calculated as
Dry bulk density = mass of soil/ volume as a whole
:
Wet bulk density = mass of soil plus liquids/ volume as a whole
:
The dry bulk density of a soil is
inversely related to the porosity of the same soil: the more pore space in a soil the lower the value for bulk density. Bulk density of a region in the interior of the Earth is also related to the
seismic velocity
A seismic wave is a mechanical wave of acoustic energy that travels through the Earth or another planetary body. It can result from an earthquake (or generally, a quake), volcanic eruption, magma movement, a large landslide and a large man ...
of waves travelling through it: for
P-wave
A P wave (primary wave or pressure wave) is one of the two main types of elastic body waves, called seismic waves in seismology. P waves travel faster than other seismic waves and hence are the first signal from an earthquake to arrive at any ...
s, this has been quantified with
Gardner's relation
Gardner's relation, or Gardner's equation, named after Gerald H. F. Gardner and L. W. Gardner, is an empirically derived equation that relates seismic P-wave velocity to the bulk density of the lithology in which the wave travels. The equation re ...
. The higher the density, the faster the velocity.
See also
*
Brazil nut effect
Granular convection is a phenomenon where granular material subjected to shaking or vibration will exhibit circulation patterns similar to types of fluid convection. It is sometimes called the Brazil nut effect, when the largest of irregularly sh ...
*
Characterisation of pore space in soil
The pore space of soil contains the liquid and gas phases of soil, i.e., everything but the solid phase that contains mainly minerals of varying sizes as well as organic compounds.
In order to understand porosity better a series of equations have ...
*
Effective porosity
*
Density meter
A density meter (densimeter) is a device which measures the density of an object or material. Density is usually abbreviated as either \rho or D . Typically, density either has the units of '' kg/m^3 '' or '' lb/ft^3 ''. The most basic principl ...
*
Number density
Notes
External links
University of Leicester podcast 'How to measure dry bulk density'
Bulk density calculator'Determination of bulk density'
{{Authority control
Mass density
Particulates
Soil physics