ASTM D7698-21
(Test Method)Standard Test Method for In-Place Estimation of Density and Water Content of Soil and Aggregate by Correlation with Complex Impedance Method
Standard Test Method for In-Place Estimation of Density and Water Content of Soil and Aggregate by Correlation with Complex Impedance Method
SIGNIFICANCE AND USE
5.1 CIMI measurements as described in this Standard Test Method are applicable to measurements of compacted soils intended for roads and foundations.
5.2 The test method is used for estimating in-place values of density and water content of soils and soil-aggregates based on electrical measurements.
5.3 The test method may be used for quality control and acceptance testing of compacted soil and soil aggregate mixtures as used in construction and also for research and development. The minimal disturbance nature of the methodology allows repetitive measurements in a single test location and statistical analysis of the results.
5.4 Limitations:
5.4.1 This test method provides an overview of the CIMI measurement procedure using a controlling console connected to a soil sensor unit which applies a 3.0 MHz RF voltage to an in-place soil via metallic probes that are driven into the soil at a prescribed distance apart. This test method does not discuss the details of the CIMI electronics, computer, or software that utilize on-board algorithms for estimating the soil density and water content
5.4.2 It is difficult to address an infinite variety of soils in this standard. However, data presented in X3.1 provides a list of soil types that are applicable for the CIMI use.
5.4.3 The procedures used to specify how data are collected, recorded, or calculated in this standard are regarded as the industry standard. In addition, they are representative of the significant digits that generally should be retained. The procedures prescribed in this standard do not consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the user’s objectives; it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations. It is beyond the scope of this standard to consider significant digits used in analytical methods for engineering design.
Note 1: Notwithstanding th...
SCOPE
1.1 Purpose and Application—This test method describes the procedure, equipment, and interpretation methods for estimating in-place soil dry density and water content using a Complex-Impedance Measuring Instrument (CIMI).
1.1.1 The purpose and application of this test method is for testing porous material such as used in roadway base or building foundations that may be deployed in the field at various test sites. The test apparatus includes electrodes that contact the porous material under test and a sensor unit that supplies electromagnetic signals to the porous material. Response signals reveal electrical parameters such as complex impedance which can be equated to material properties such as density and moisture content.
1.1.2 CIMI measurements as described in this test method are applicable to measurements of compacted soils intended for roads and foundations.
1.1.3 This test method describes the procedure for estimating in-place density and water content of soils and soil-aggregates by use of a CIMI. The electrical properties of the soil are measured using a radio frequency (RF) voltage source connected to soil electrical probes driven into the soils and soil-aggregates to be tested, in a prescribed pattern and depth. Certain algorithms of these properties are related to wet density and water content. This correlation between electrical measurements, and density and water content is accomplished using a calibration methodology. In the calibration methodology, density and water content are determined by other ASTM Test Standards that measure soil density and water content, thereafter correlating the corresponding measured electrical properties to the soil physical properties.
1.2 Units—The values stated in SI units are to be regarded as standard. The inch-pound units given in parentheses are mathematical conversions which are provided for information purposes only and are not considered standard.
1.2.1...
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This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7698 − 21
Standard Test Method for
In-Place Estimation of Density and Water Content of Soil
and Aggregate by Correlation with Complex Impedance
1
Method
This standard is issued under the fixed designation D7698; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* mathematical conversions which are provided for information
purposes only and are not considered standard.
1.1 Purpose and Application—This test method describes
1.2.1 All observed and calculated values shall conform to
the procedure, equipment, and interpretation methods for
the guidelines for significant digits and rounding established in
estimating in-place soil dry density and water content using a
Practice D6026 unless superseded by this standard.
Complex-Impedance Measuring Instrument (CIMI).
1.1.1 The purpose and application of this test method is for
1.3 Generalized Theory:
testing porous material such as used in roadway base or
1.3.1 Two key electrical properties of soil are conductivity
building foundations that may be deployed in the field at
and relative dielectric permittivity which are manifested as a
various test sites. The test apparatus includes electrodes that
value of complex-impedance that can be determined.
contact the porous material under test and a sensor unit that
1.3.2 The soil conductivity contributes primarily to the real
supplies electromagnetic signals to the porous material. Re-
component of the complex-impedance, and the soil relative
sponse signals reveal electrical parameters such as complex
dielectric permittivity contributes primarily to the imaginary
impedance which can be equated to material properties such as
component of the complex-impedance.
density and moisture content.
1.3.3 The complex-impedance of soil can be determined by
1.1.2 CIMI measurements as described in this test method
placing two electrodes in the soil to be tested at a known
areapplicabletomeasurementsofcompactedsoilsintendedfor
distance apart and a known depth. The application of a known
roads and foundations.
frequency of alternating current to the electrodes enables a
1.1.3 This test method describes the procedure for estimat-
measurement of current through the soil, voltage across the
ing in-place density and water content of soils and soil-
electrodes, and the electrical phase difference between the
aggregates by use of a CIMI. The electrical properties of the
voltage and current. Complex-impedance is calculated from
soil are measured using a radio frequency (RF) voltage source
these known and measured parameters.
connected to soil electrical probes driven into the soils and
1.3.4 From the determined complex-impedance, an electri-
soil-aggregates to be tested, in a prescribed pattern and depth.
cal network consisting of a resistor (R) and capacitor (C)
Certainalgorithmsofthesepropertiesarerelatedtowetdensity
connected in parallel are used to represent a model of the soil
and water content. This correlation between electrical
being tested.
measurements, and density and water content is accomplished
1.3.5 Relationships can be made between the soil wet
using a calibration methodology. In the calibration
density and the magnitude of the complex-impedance, and also
methodology, density and water content are determined by
between the soil water mass per unit measured, and the
otherASTMTestStandardsthatmeasuresoildensityandwater
quotient of the values of C and R using a Soil Model process.
content, thereafter correlating the corresponding measured
1.3.6 The Soil Model process results in mathematical rela-
electrical properties to the soil physical properties.
tionships between the physical and electrical characteristics of
1.2 Units—The values stated in SI units are to be regarded
thesoilwhichareusedforsoil-specificcalibrationoftheCIMI.
as standard. The inch-pound units given in parentheses are
1.3.7 Refer to Appendix X1 for a more detailed explanation
of complex-impedance measurement of in-place soil, and its
use in field measurements for the estimation of dry density and
1
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
water content.
Rock and is the direct responsibility of Subcommittee D18.08 on Special and
Construction Control Tests.
1.4 Precautions:
Current edition approved May 1, 2021. Published May 2021. Originally
1.4.1 The low-level RF output power levels of the CIMI
approved in 2011. Last previous edition approved in 2020 as D7698–20. DOI
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7698 − 20 D7698 − 21
Standard Test Method for
In-Place Estimation of Density and Water Content of Soil
and Aggregate by Correlation with Complex Impedance
1
Method
This standard is issued under the fixed designation D7698; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Scope*
1.1 Purpose and Application—This test method describes the procedure, equipment, and interpretation methods for estimating
in-place soil dry density and water content using a Complex-Impedance Measuring Instrument (CIMI).
1.1.1 The purpose and application of this test method is for testing porous material such as used in roadway base or building
foundations that may be deployed in the field at various test sites. The test apparatus includes electrodes that contact the porous
material under test and a sensor unit that supplies electromagnetic signals to the porous material. Response signals reveal electrical
parameters such as complex impedance which can be equated to material properties such as density and moisture content.
1.1.2 CIMI measurements as described in this test method are applicable to measurements of compacted soils intended for roads
and foundations.
1.1.3 This test method describes the procedure for estimating in-place density and water content of soils and soil-aggregates by
use of a CIMI. The electrical properties of the soil are measured using a radio frequency (RF) voltage source connected to soil
electrical probes driven into the soils and soil-aggregates to be tested, in a prescribed pattern and depth. Certain algorithms of these
properties are related to wet density and water content. This correlation between electrical measurements, and density and water
content is accomplished using a calibration methodology. In the calibration methodology, density and water content are determined
by other ASTM Test Standards that measure soil density and water content, thereafter correlating the corresponding measured
electrical properties to the soil physical properties.
1.2 Units—The values stated in SI units are to be regarded as standard. The inch-pound units given in parentheses are
mathematical conversions which are provided for information purposes only and are not considered standard.
1.2.1 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice
D6026 unless superseded by this standard.
1.3 Generalized Theory:
1.3.1 Two key electrical properties of soil are conductivity and relative dielectric permittivity which are manifested as a value of
complex-impedance that can be determined.
1
This test method is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.08 on Special and Construction
Control Tests.
Current edition approved June 1, 2020May 1, 2021. Published June 2020May 2021. Originally approved in 2011. Last previous edition approved in 20192020 as
D7698–19.–20. DOI: 10.1520/D7698-20.10.1520/D7698-21.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
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D7698 − 21
1.3.2 The soil conductivity contributes primarily to the real component of the complex-impedance, and the soil relative dielectric
permittivity contributes primarily to the imaginary component of the complex-impedance.
1.3.3 The complex-impedance of soil can be determined by placing two electrodes in the soil to be tested at a known distance apart
and a known depth. The application of a known frequency of alternating current to the electrodes enables a measurement of current
through the soil, voltage across the electrodes, and the electrical phase difference between the voltage and current.
Complex-impedance is calculated from these known and measured parameters.
1.3.4 From the determined complex-impedance, an electrical network consisting of a resistor (R) and capacitor (C) connected in
parallel are used to represent a model of the soil being tested.
1.3.5 Relationships can be made between the soil wet density and the magnitude of the complex-impedance, and also between the
soil water mass per unit measured, and the quotient of the valu
...
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