ISO/DIS 16383-2:2026(en)
ISO TC 182
Secretariat: BSI
Date:2025-11-14
Geotechnical investigation and testing – Laboratory testing of rock –
Part 2: Determination of density and open porosity
© ISO 2026, Published in Switzerland
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Contents
6.1.1 Specimen size requirements 10
6.1.2 Test specimen preparation 10
6.2 Determination of bulk mass 10
6.3 Determination of grain mass 10
6.4 Determination of submerged mass using the immersion method 12
6.5 Determination of bulk volume using the linear method 12
6.6 Determination of grain volume using gas pycnometry 13
7.2 Linear method combined with gas pycnometry 16
Annex A (Normative) Calibration, maintenance, and checks 20
Annex B (Informative) Volume determination 22
Foreword
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This document was prepared by Technical Committee ISO/TC 182, [Geotechnical investigation and testing], Subcommittee WG 10, [Laboratory testing of rock].
A list of all parts in the ISO 16 383 series can be found on the ISO website.
Introduction
This document covers areas in the international field of geotechnical engineering never previously standardized internationally. It is intended that this document presents broad good practice throughout the world and significant differences with national documents is not anticipated. It is based on international practice (see Reference [1]).
Geotechnical investigation and testing – Laboratory testing of rock – Part 2: Determination of density and open porosity
1.0 Scope
This document specifies the procedure for determining bulk, dry and grain densities as well as open porosity of a rock specimen using the immersion method and a combination of the linear method and gas pycnometry.
This document is applicable to the laboratory determination of density and open porosity of a rock test specimen within the scope of geotechnical investigations.
Other methods for determining the bulk mass, grain mass, bulk volume and grain volume of the specimen that fulfil the requirements set in this document may also be considered acceptable (Annex B). Used method should be chosen based on the use case (type of specimen, availability etc.).
Bulk, dry and grain density as well as open porosity are determined for the specimen as is and are dependent on fluid content, which shall be determined and reported as per ISO 16383-1.
NOTE: This document fulfils the requirements of the determination of bulk density of rock for geotechnical investigation and testing in accordance with EN 1997-2 (2024).
2.0 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 14689, Geotechnical investigation and testing — Identification, description and classification of rock
ISO 16383‑1, Geotechnical investigation and testing — Laboratory testing of rock — Part 1: Determination of water content
ISO 12154, Determination of density by volumetric displacement — Skeleton density by gas pycnometry
3.0 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1
Saturation fluid
the fluid used to saturate the specimen
Note 1 to entry: saturation fluid must be reported.
3.2
Immersion liquid
the liquid the specimen is immersed in, typically water
Note 1 to entry: immersion liquid must be reported.
3.3
Open void
void that can be penetrated by the saturation fluid
3.4
Closed void
void that cannot be penetrated by the saturation fluid
3.5
Void volume
volume of open voids
3.6
Grain volume
volume of the rock matrix, including closed voids, but excluding open voids
3.7
Grain mass
mass of the rock matrix, including closed voids, but excluding open voids
3.8
Bulk volume
total volume of the specimen, including the rock matrix, and open and closed void volumes
3.9
Bulk mass
total mass of the specimen, including the rock matrix, and open and closed void volumes
3.10
Submerged mass
total mass of the specimen, including the rock matrix, and open and closed void volumes, submerged in the immersion liquid
3.11
Water density
density of water, a constant value of 0,998 2 g/cm3 corresponding to the density of pure water at 20 °C (IAPWS95-2018) is used in this document
3.12
Immersion liquid density
density of the immersion liquid
3.13
Water content
ratio of the mass of free water to the mass of the dry specimen, to be determined as per ISO 16383-1
3.14
Density
mass of a substance per unit of volume, also known as specific mass
3.15
Specific gravity
ratio of the density of a substance to the density of a given reference material, typically water at its densest (at 4 °C), also known as relative density
3.16
Bulk density
bulk mass of the rock specimen divided by its bulk volume, also known as apparent density
3.17
Dry density
grain mass of the rock specimen divided by its bulk volume
Note 1 to entry: specimen is considered fully dried when it has been dried to a constant mass as per ISO 16383-1.
3.18
Grain density
grain mass of the rock specimen divided by its grain volume, also known as matrix density or particle density
3.19
Open porosity
the ratio of void volume to bulk volume
3.20
Constant mass
the point at which there is less than 0,1 % further change in mass of the rock test specimen when dried for a further period of at least 1 h, over three consecutive measurements, as described in ISO 16383-1
3.21
Representative specimen
a specimen chosen by a qualified person associated with the characteristic features of the rock mass
4.0 Symbols and units
VV | void volume | (cm3) |
VG | grain volume | (cm3) |
MG | grain mass | (g) |
V | bulk volume | (cm3) |
M | bulk mass | (g) |
MS | submerged mass | (g) |
ρW | water density | (g/cm3) |
ρL | immersion liquid density | (g/cm3) |
w | water content | (%) |
r | radius of the specimen | (cm) |
h | height of the specimen | (cm) |
L1 | length of the longest dimension of the specimen | (cm) |
L2 | length of the second longest dimension of the specimen | (cm) |
L3 | length of the shortest dimension of the specimen | (cm) |
V1 | volume of the sample chamber | (cm3) |
V2 | volume of the reference chamber | (cm3) |
p1 | equilibrated gauge pressure prior to expansion | (Pa) |
p2 | equilibrated gauge pressure after expansion | (Pa) |
ρ | bulk density | (g/cm3) |
ρG | grain density | (g/cm3) |
ρD | dry density | (g/cm3) |
P | open porosity | (%) |
NOTE: Here r refers to the radius of a cylindrical or spherical specimen, h refers to the height of a cylindrical specimen, and L1, L2 and L3 refer to the dimensions of a rectangular cuboid specimen.
5.0 Equipment
5.1 General
See normative ANNEX A for calibration requirements of the following equipment.
5.1.1 Straight edge
Straight edge, with a maximum deviation from straightness of 0,1 % of the measured length.
5.1.2 Callipers
Callipers, either analogue or digital, with a maximum permissible error of 0,05 mm or 0,1 % of the measured length whichever value is the greatest.
5.1.3 Balance
Balance, with a maximum permissible error of 0,01 g or 0,1 % of the weighted mass whichever is greater.
5.1.4 Gas pycnometer
Gas pycnometer conforming to ISO 12154, with a maximum permissible error of 0,1 cm3 or 0,1 % of the measured volume whichever is the greatest.
5.1.5 Drying oven
Drying oven of the forced-draft type and capable of maintaining a uniform temperature throughout the drying chamber.
5.1.6 Thermometer or thermocouple device
Thermometer or thermocouple device, with a maximum permissible error of 0,5 °C and a resolution of 0,1 °C.
5.1.7 Relative humidity
Hygrometer, with a maximum permissible error of 5 % and a resolution of 1 %.
5.1.8 Test specimen container
Test specimen container (with or without a lid) shall be constructed of a material that does not change mass because of repeated drying cycles.
5.1.9 Desiccator
Desiccator, if used shall be of suitable size and contain dry, self-indicating desiccant, such as silica gel.
Desiccator shall have a capacity large enough to hold the test specimen to be dried but should not be so large that the mass of the empty desiccator is significantly in excess of that of the test specimen.
Desiccator with tight-fitting lids should be used.
6.0 Test procedure
6.1 General
The flow chart presented below summarizes the steps for the determination of bulk, grain and dry densities as well as open porosity using either the immersion method or a combination of the linear method and gas pycnometry (Figure 1).
Figure 1 — Flow chart for the determination of bulk, grain and dry densities as well as open porosity using either the immersion method or a combination of the linear method and gas pycnometry.
6.1.1 Specimen size requirements
The test specimen should have a mass of at least 50 g and a minimum size of ten times the maximum grain or pore size whichever is greater.
NOTE: The accuracy of the balance used must be chosen according to the mass of the test specimen.
For gas pycnometry, the test specimen size shall be selected in accordance with the specifications of the used pycnometer or have a minimum volume of 20 cm3 whichever is limiting.
A representative specimen of the rock shall be selected.
NOTE: The way the test specimen is selected, and its required mass is dependent on the purpose (application) of the test, the type of rock being tested and the type of specimen (e.g., test specimen from another test).
6.1.2 Test specimen preparation
The specimen shall be cleaned from any undesired loose material, ensuring no damage is done.
NOTE: A soft paintbrush can be used to clean the specimen before the first weighing. If it is not sufficient, the loose material could be scraped off.
For the linear method, the specimen shall be shaped to the form of a right circular cylinder or a rectangular cuboid, with the faces of the specimen level to 0,05 mm and perpendicular to 0,05°.
It shall be ensured that the specimen is fully saturated with the immersion liquid prior to the determination of bulk mass and submerged mass.
6.2 Determination of bulk mass
The specimen shall be placed in a clean, dry container of a known mass.
Bulk mass (M) of the specimen shall be determined.
6.2.1 Determination of grain mass
The specimen shall be placed in a clean, dry container of a known mass.
The container (open container if a lid is used previously) with the specimen shall be placed in a drying oven maintained at 105 °C / 110 °C or any temperature in between for at least 16 hours and dried to a constant mass.
For rock containing gypsum or other minerals having a significant amount of chemically bonded water, the mass change on drying may not just be due to the loss of free water. In these circumstances, drying at a lower temperature, below 60 °C, shall be performed providing that the dry mass is determined using this constant mass method.
NOTE: The time required to obtain constant mass will vary depending on the rock type, size of test specimen, oven type and capacity, and other factors. The influence of these factors generally can be established by good judgement and with experience of the rocks being tested and the apparatus being used.
After the test specimen is dried to a constant mass, it shall be removed from the oven and placed in a desiccator to keep the test specimen dry until it cools to room temperature for weighing.
Alternatively, a tight-fitting-lid should be used to prevent any exchange of water with the atmosphere of the room.
If any condensation occurs on the container and the lid, it shall be wiped off before weighing.
Grain mass of the dried test specimen (MG) shall be determined.
Relative humidity shall be determined.
NOTE: Balances are susceptible to small errors when weighing hot items due to convection currents set up by localized heating of air around the balance.
The flow chart presented below summarizes the steps of the procedure for the determination of grain mass (Figure 2).
Figure 2 — Test procedure flow chart for the determination of grain mass
6.2.2 Determination of submerged mass using the immersion method
A balance shall be supported with a platform over a container with sufficient clearance between the underside of the supports and the top of the container.
A cradle shall be suspended from the supporting frame and lowered into the container so that it does not touch the bottom or the sides of the container.
The container shall be filled with the immersion liquid so that the specimen shall be completely submerged when on the cradle.
The specimen shall be placed in the cradle so that it is fully submerged, taking care that no air bubbles are trapped underneath the specimen.
The surface of the immersion liquid shall be given sufficient time to settle.
NOTE: Measurements can proceed once the balance reading has stabilized.
Submerged mass (MS) of the specimen shall be determined.
Ambient temperature and immersion liquid temperature shall be determined.
The flow chart presented below summarizes the steps of the procedure for the determination of submerged mass using the immersion method (Figure 3).
Figure 3 — Test procedure flow chart for the determination of submerged mass using the immersion method.
6.2.3 Determination of bulk volume using the linear method
For a right circular cylinder rock specimen, diameter and height (h) shall be determined as the average of measurements in three evenly spaced directions.
For a right circular cylinder rock specimen, radius (r) of the specimen shall be determined as half of its diameter.
For a rectangular cuboid rock specimen, lengths (L1, L2 and L3) of its sides in each of the three perpendicular directions shall be determined as the average of measurements in three evenly spaced positions.
Bulk volume (V) of the rock specimen shall be determined from its dimensions.
The flow chart presented below summarizes the steps of the procedure for the determination of bulk volume using the linear method (Figure 4).
Figure 4 — Test procedure flow chart for the determination of bulk volume using the linear method.
6.2.4 Determination of grain volume using gas pycnometry
A dried rock specimen shall be placed in the sample chamber of the pycnometer.
NOTE: The volume of the sample chamber (V1) and the reference chamber (V2) must be known.
Equilibrated gauge pressure prior to expansion (p1) and after expansion (p2) shall be determined according to ISO 12154.
Grain volume (VG) of the specimen shall be determined according to ISO 12154.
The flow chart presented below summarizes the steps of the procedure for the determination of grain volume using gas pycnometry (Figure 5).
Figure 5 — Test procedure flow chart for the determination of grain volume using gas pycnometry.
7.0 Test results
7.1 Immersion method
Using the immersion method, the following calculations shall be performed.
NOTE: These equations assume the closed pores to have a net zero effect on specimen buoyancy.
NOTE: A constant value of 0,9982 g/cm3 corresponding to the density of pure water at 20 °C (IAPWS95-2018) is used for water density. Report water temperature if it deviates significantly from 20 °C.
7.1.1 Bulk density
Bulk density of the specimen shall be calculated according to Formula (1):
(1)
where
ρ is the bulk density (g/cm3).
M is the bulk mass (g).
MS is the submerged mass (g).
ρL is the immersion liquid density (g/cm3).
7.1.2 Grain density
Grain density of the specimen shall be calculated according to Formula (2):
(2)
where
ρG is the grain density (g/cm3).
MG is the grain mass (g).
MS is the submerged mass (g).
ρL is the immersion liquid density (g/cm3).
7.1.3 Dry density
Dry density of the specimen shall be calculated according to Formula (3):
(3)
where
ρD is the dry density (g/cm3).
M is the bulk mass (g).
MG is the grain mass (g).
MS is the submerged mass (g).
ρL is the immersion liquid density (g/cm3).
7.1.4 Open porosity
Open porosity of the specimen shall be calculated according to Formula (4):
(4)
where
P is the open porosity (%).
M is the bulk mass (g).
MG is the grain mass (g).
MS is the submerged mass (g).
7.2 Linear method combined with gas pycnometry
7.2.1 Bulk density
Bulk density of a right circular cylinder specimen shall be calculated according to Formula (5):
(5)
where
ρ is the bulk density (g/cm3).
M is the bulk mass (g).
r is the radius of the specimen (cm).
h is the height of the specimen (cm).
Bulk density of a rectangular cuboid specimen shall be calculated according to Formula (6):
(6)
where
ρ is the bulk density (g/cm3).
M is the bulk mass (g).
L1 is the length of the longest dimension of the specimen (cm).
L2 is the length of the second longest dimension of the specimen (cm).
L3 is the length of the shortest dimension of the specimen (cm).
7.2.2 Grain density
Grain density of the specimen shall be calculated according to Formula (7):
(7)
where
ρG is the grain density (g/cm3).
MG is the grain mass (g).
V1 is the volume of the sample chamber (cm3).
V2 is the volume of the reference chamber (cm3).
p1 equilibrated gauge pressure prior to expansion (Pa).
p2 equilibrated gauge pressure after expansion (Pa).
7.2.3 Dry density
Dry density of a right circular cylinder specimen shall be calculated according to Formula (8):
(8)
where
ρD is the dry density (g/cm3).
MG is the grain mass (g).
r is the radius of the specimen (cm).
h is the height of the specimen (cm).
Dry density of a rectangular cuboid specimen shall be calculated according to Formula (9):
(9)
where
ρD is the dry density (g/cm3).
MG is the grain mass (g).
L1 is the length of the longest dimension of the specimen (cm).
L2 is the length of the second longest dimension of the specimen (cm).
L3 is the length of the shortest dimension of the specimen (cm).
7.2.4 Open porosity
Open porosity of a right circular cylinder specimen shall be calculated according to Formula (10):
(10)
where
P is the open porosity (%).
r is the radius of the specimen (cm).
h is the height of the specimen (cm).
V1 is the volume of the sample chamber (cm3).
V2 is the volume of the reference chamber (cm3).
p1 equilibrated gauge pressure prior to expansion (Pa).
p2 equilibrated gauge pressure after expansion (Pa).
Open porosity of a rectangular cuboid specimen shall be calculated according to Formula (11):
(11)
where
P is the open porosity (%).
L1 is the length of the longest dimension of the specimen (cm).
L2 is the length of the second longest dimension of the specimen (cm).
L3 is the length of the shortest dimension of the specimen (cm).
V1 is the volume of the sample chamber (cm3).
V2 is the volume of the reference chamber (cm3).
p1 equilibrated gauge pressure prior to expansion (Pa).
p2 equilibrated gauge pressure after expansion (Pa).
8.0 Test report
The test report shall affirm that the test was carried out in accordance with this document and shall include the following information:
a) method(s) used.
b) identification of the specimen tested, e.g., by hole number, specimen number and specimen depth and any other relevant details required, e.g., depth of specimen within a specimen, method of specimen selection if relevant.
c) a visual geological description of the specimen tested including any observed features noted after testing, following the principles in ISO 14689.
d) specimen shape and size.
e) a reference to this document (ISO 16383-2).
f) bulk, dry and grain density as well as open porosity, or any combination thereof as required, expressed to three significant digits.
g) water content of the specimen reported in accordance with ISO 16383-1.
h) ambient temperature and relative humidity.
i) any deviation from this procedure.
j) any special event(s) which occurred during the test.
(Normative)
Calibration, maintenance, and checks- General requirements
All measurement equipment used in this document shall be calibrated periodically, its performance shall be checked where required at intervals, and it shall be operated in a controlled environment if so specified. This Annex defines these requirements for this method.
If calibration of measurement equipment is carried out by a third party, it shall be carried out by an accredited calibration laboratory. The certification shall show traceability to recognised national or international standards of measurement.
Where calibration of test measuring equipment is conducted in-house, the laboratory shall hold appropriate reference standards or instruments that are used solely for calibration purposes. These should be calibrated by an accredited calibration laboratory with certification requirements as above. When not in use reference measurement equipment should be retained securely in a suitable environment separate from working standards or instruments. Reference standards and instruments shall be at least as accurate as the working device so that the desired accuracy of test measurement is achieved.
In house calibration procedures shall be documented, shall only be performed by approved persons and records of such calibrations, and of performance checks, shall be retained on file.
Notwithstanding the required calibration or check intervals in this Annex, whenever any item of reference equipment or test measurement equipment has been mishandled, repaired, dismantled, adjusted or overhauled it shall be recalibrated before further use.
All calibrated equipment shall be used only within the range for which it has been calibrated.
- Environmental conditions
There are no specific environmental conditions applicable to the execution of this test method. The temperature and relative humidity shall be recorded.
- Equipment specifications
- Ovens
- Equipment specifications
The set temperature of an empty oven shall be checked by means of a calibrated temperature measuring device, undertaken close to the centre of the usable oven space at least once a year. The temperature distribution of an empty oven shall be checked before first use and after any major repair or replacement of heater elements and/or thermostat. If any of the individual temperature points is found to be outside the specified range of the set temperature, remedial action shall be taken.
Table A.1 — Maximum permissible error for the oven's temperatures
Oven temperature | 50 °C to 55 °C | 105 °C to 110 °C |
Maximum permissible error | ±5 °C | ±5 °C |
This maximum permissible error is to consider the stability of the oven is given in Table A.1.
- Thermometers
If thermocouples are used for verifying oven temperatures, they shall be calibrated against a reference thermocouple, reference platinum resistance thermometer or reference liquid-in-glass thermometer before first use and thereafter at least once a year.
- Hygrometer
Hygrometers shall be calibrated over their working range, using certified reference procedure at least once a year.
- Balances
Balances shall be calibrated over their working range, using certified reference weights, at least once a year in the location in which they are used. Reference weights shall be appropriate to the category of balance being calibrated and shall have a tolerance (maximum permissible error) better than the resolution of the balance to be calibrated. Reference weights shall be calibrated when first brought into use and thereafter at least every two years.
Balances shall be checked on each day of use to confirm the zero point and to confirm the mass of a test item of known mass. The test item should not corrode or otherwise change mass with time. The results of these checks shall be recorded. If the balance cannot be zeroed or the mass of the test weight is found to be outside the tolerance specified in 4.3, the balance shall be taken out of service until remedial action is complete.
- Straight edge, callipers and both direct and indirect methods of length measurement
Straight edge, callipers shall be calibrated against reference gauge blocks or a reference calliper for both internal and external measurements. Reference gauge blocks shall be calibrated at least every five years. Reference and working callipers shall be calibrated at least every year.
For indirect, no contact methods, working reference blocks of the size, shape and optical properties shall be used. Reference blocks shall be calibrated at least every year.
(Informative)
Volume determination
A number of well-established methods exist for the determination of bulk and/or grain volume that may be suitable for use on rock specimens. Exhaustive documentation of all methods cannot be described in this document. However, volume determination methods that may also be suitable include:
a) Fluid displacement method
b) Glass bead method
c) Laser volumetry
d) Acoustic volumetry
e) Various 3D scanning methods
f) Various tomography methods
If a method other than the immersion method, linear method or gas pycnometry are used, the results shall be reported as a deviation from this document and the following considerations made:
— Care should be taken to select the method most appropriate to the material to be tested, as incorrect results may be derived from a method that is not well suited to the particular type of rock.
— Particular care should be exercised with swelling rock, specimens with irregular external surfaces, and sensitive specimens.
— The selected method(s) shall fulfil the requirements set out in this document and produce results with comparable accuracy.
— Calibration and accuracy of the used method shall be carefully documented.
Bibliography
[1] ISO 14689, Geotechnical investigation and testing — Identification, description and classification of rock
[2] ISO 16383‑1, Geotechnical investigation and testing — Laboratory testing of rock — Part 1: Determination of water content
[3] ISO 12154, Determination of density by volumetric displacement — Skeleton density by gas pycnometry
[4] International Association for the Properties of Water and Steam (2018). Revised Release on the IAPWS Formulation 1995 for the Thermodynamic Properties of Ordinary Water Substance for General and Scientific Use. IAPWS R6-95(2018).
