ASTM D6938-17
Standard Test Methods for In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth)

Standard No.

ASTM D6938-17

Release Date

2017

Published By

American Society for Testing and Materials (ASTM)

Status

Be replaced

Replace By

ASTM D6938-17a

Latest

ASTM D6938-23

Scope

1.1 This test method describes the procedures for measuring in-place density and moisture of soil and soil-aggregate by use of nuclear equipment (hereafter referred to as “gauge”). The density of the material may be measured by direct transmission, backscatter, or backscatter/air-gap ratio methods. Measurements for water (moisture) content are taken at the surface in backscatter mode regardless of the mode being used for density. 1.1.1 For limitations see Section 5 on Interferences. 1.2 The total or wet density of soil and soil-aggregate is measured by the attenuation of gamma radiation where, in direct transmission, the source is placed at a known depth up to 300 mm (12 in.) and the detector(s) remains on the surface (some gauges may reverse this orientation); or in backscatter or backscatter/air-gap the source and detector(s) both remain on the surface. 1.2.1 The density of the test sample in mass per unit volume is calculated by comparing the detected rate of gamma radiation with previously established calibration data. 1.2.2 The dry density of the test sample is obtained by subtracting the water mass per unit volume from the test sample wet density (Section 11). Most gauges display this value directly. 1.3 The gauge is calibrated to read the water mass per unit volume of soil or soil-aggregate. When divided by the density of water and then multiplied by 100, the water mass per unit volume is equivalent to the volumetric water content. The water mass per unit volume is determined by the thermalizing or slowing of fast neutrons by hydrogen, a component of water. The neutron source and the thermal neutron detector are both located at the surface of the material being tested. The water content most prevalent in engineering and construction activities is known as the gravimetric water content, w, and is the ratio of the mass of the water in pore spaces to the total mass of solids, expressed as a percentage. 1.4 Two alternative procedures are provided. 1.4.1 Procedure A describes the direct transmission method in which the probe extends through the base of the gauge into a pre-formed hole to a desired depth. The direct transmission is the preferred method. 1.4.2 Procedure B involves the use of a dedicated backscatter gauge or the probe in the backscatter position. This places the gamma and neutron sources and the detectors in the same plane. 1.4.3 Mark the test area to allow the placement of the gauge over the test site and to align the probe to the hole. 1.5 SI Units—The values stated in SI units are to be regarded as the standard. The values in inch-pound units (ft – lb units) are provided for information only. 1.6 All observed and calculated values shall conform to the guide for significant digits and rounding established in Practice D6026. 1.6.1 The procedures used to specify how data are collected, recorded, and calculated in this standard are regarded as the industry standard. In addition, they are representative of the significant digits that should generally be retained. The procedures used do not consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the user’s objectives; and 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 analysis methods for engineering design. 1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the 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 March 1, 2017. Published March 2017. Originally approved in 2006. Last previous edition approved in 2015 as D6938–15. DOI: 10.1520/D6938-17. *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 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. 1 responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

ASTM D6938-17 Referenced Document

• ASTM D1556 Standard Test Method for Density and Unit Weight of Soil in Place by the Sand-Cone Method*， 2024-04-22 Update
• ASTM D1557 Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort (56,000 ft-lbf/ft³ (2,700 kN-m/m³))
• ASTM D2167 Standard Test Method for Density and Unit Weight of Soil in Place by the Rubber Balloon Method
• ASTM D2216 Standard Test Method for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
• ASTM D2487 Standard Test Method for Classification Of Soils For Engineering Purposes
• ASTM D2488 Recommended Practice for Description Of Soils (Visual-Manual Procedure)
• ASTM D2937 Standard Test Method for Field Determination of Soil Density by the Pushing Cylinder Method*， 2024-04-22 Update
• ASTM D3740 Standard Practice for Minimum Requirements for Agencies Engaged in the Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• ASTM D4253 Standard test method for maximum index density and unit weight of soil using a shaking table*， 2024-04-22 Update
• ASTM D4254 Standard Test Methods for Minimum Index Density and Unit Weight of Soils and Calculation of Relative Density*， 2024-04-22 Update
• ASTM D4643 Standard Test Method for Determination of Water Content of Soil and Rock by Microwave Oven Heating
• ASTM D4718 Standard Practice for Correction of Unit Weight and Water Content for Soils Containing Oversize Particles
• ASTM D4944 Standard Test Method for Field Determination of Water (Moisture) Content of Soil by the Calcium Carbide Gas Pressure Tester Method
• ASTM D4959 Standard Test Method for Determination of Water Content of Soil By Direct Heating*， 2024-02-01 Update
• ASTM D6026 Standard Practice for Using Significant Digits in Geotechnical Data
• ASTM D653 Standard Terminology Relating to Soil, Rock, and Contained Fluids
• ASTM D698 Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort (12 400 ft-lbf/ft³ (600 kN-m/m³))*， 2024-04-22 Update
• ASTM D7013 Standard Guide for Nuclear Surface Moisture and Density Gauge Calibration Facility Setup
• ASTM D7759 Standard Guide for Nuclear Surface Moisture and Density Gauge Calibration

ASTM D6938-17 history

• 2023 ASTM D6938-23 Standard Test Methods for In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth)
• 2017 ASTM D6938-17ae1 Standard Test Methods for In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth)
• 2017 ASTM D6938-17a Standard Test Methods for In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth)
• 2017 ASTM D6938-17 Standard Test Methods for In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth)
• 2015 ASTM D6938-15 Standard Test Methods for In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth)
• 2010 ASTM D6938-10 Standard Test Method for In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth)
• 2008 ASTM D6938-08a Standard Test Method for In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth)
• 2008 ASTM D6938-08 Standard Test Method for In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth)
• 2007 ASTM D6938-07b Standard Test Method for In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth)
• 2007 ASTM D6938-07a Standard Test Methods for In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth)
• 2007 ASTM D6938-07 Standard Test Methods for In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth)
• 2006 ASTM D6938-06e1 Standard Test Methods for In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth)