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Home My WebLink AboutDSHW-2024-008197 Clean Harbors Grassy Mountain, LLC P.O. Box 22750 Salt Lake City, UT 84122 Tel: 435.884.8900 Fax: 435.884.8990 www.cleanharbors.com “People and Technology Creating a Better Environment” September 5, 2024 Mr. Doug Hansen, Director Division of Waste Management and Radiation Control Utah Department of Environmental Quality 195 North 1950 West P.O. Box 144880 Salt Lake City, UT 84114‐4880 RE: Change Control Procedures – Density Gauge Cell 10 Construction, Clean Harbors Grassy Mountain, LLC; EPA ID No. UTD991301748 Dear Mr. Hansen, In accordance with its Resource Conservation and Recovery Act (RCRA) Part B Permit No. UTD991301748 (the “Permit”) Attachment VI‐3 “Construction Quality Assurance (CQA) Plan for Construction of Surface Impoundments, Landfills, and Landfill Closures” Part 5.0, Clean Harbors Grassy Mountain (CHGM or the “Facility”) is submitting a letter with attachment from CQA Engineer Hansen, Allen & Luce (HA&L) pertaining to Change Control Procedures. The HA&L letter recommends that a Troxler eGauge 4590 be approved as equivalent or better to the previous Troxler models 3440 or 4640‐B for testing soil compaction/density. This constitutes a minor change in accordance with CQA Plan Part 5.C.1., in which minor changes are defined as “all changes that will in no way affect the performance standard or the original intent of the plans and specification approved by UDWMRC [Utah Division of Waste Management and Radiation Control],” and “changes in testing procedures (ASTM updates)” are included as an example. Such minor changes are allowed without prior approval of UDWMRC provided the requirements of Part 5.C.1. are met. Specifically, HA&L recommends the use of the Troxler eGauge 4590 (for wet density only), based on accepting ASTM D8167 as an alternative to ASTM D6938, which is defined in Appendix A‐1 to the Facility’s CQA Plan. A copy of ASTM D8167 Standard Test Method is included with the attached letter. “I certify under penalty of law that this document and all attachments were prepared under my direction or supervision in accordance with a system designed to assure that qualified personnel properly gather and evaluate the information submitted. Based on my inquiry of the person or persons who manage the system, or those persons directly responsible for gathering the information, the information submitted is, to the best of my knowledge and belief, true accurate, and complete. I am aware that there are Mr. Hansen – UDEQ Page 2 Change Control Procedures – Density Guage Cell 10 Construction; CHGM September 5, 2024 “People and Technology Creating a Better Environment” significant penalties for submitting false information, including the possibility of fines and imprisonment for knowing violation.” If you have any questions, please contact me at torstenson.jared@cleanharbors.com or 719‐760‐2526, or Facility General Manager Shane Whitney at whitney.shane@cleanharbors.com or 435‐884‐8976. Sincerely, Jared Torstenson, P.E. Director of Environmental Compliance, Landfills Clean Harbors Environmental Services, Inc. Attachment cc: Kari Lundeen, Environmental Specialist, Hazardous Waste Section, UDEQ Jeff Coombs, EHS, Health Officer, Tooele County Health Department Bryan Slade, Environmental Health Director, Tooele County Health Department Faizur Khan, P.E., VP Landfill Construction, Clean Harbors Shane Whitney, Facility General Manager, Clean Harbors Michael Crisenbery, SVP Environmental Compliance, Clean Harbors Alan Jay Adair, SVP Facility Operations, Clean Harbors Christine Sawyer, Environmental Compliance Manager, Clean Harbors SALT LAKE AREA OFFICE 859 W South Jordan Pkwy, Ste 200 South Jordan, Utah 84095 Phone: (801) 566-5599 www.HALengineers.com C E L E B R A T I N G F I F T Y Y E A R S O F E N G I N E E R I N G E X C E L L E N C E 1 9 7 4 • 2 0 2 4 July 4, 2024 Mr. Jared Torstenson Director of Environmental Compliance Clean Harbors C/O: Mr. Faizur Khan Vice President of Landfill Engineering Dear Mr. Torstenson: Clean Harbors’ ongoing mining and excavation work, in preparation for the Grassy Mountain Facility Cell 10 construction, started in the summer of 2024. The construction of the new cell is slated for spring 2025. In anticipation of the work, Hansen, Allen & Luce plans to use the Troxler eGauge 4590 to test soil compaction/density as opposed to the traditional Troxler models 3440 or 4640-B. The eGauge utilizes a Cesium-137 radioactive source that is exempt from radioactive materials licensure, eliminating the need for specialized training, dosimeter requirements, etc. Studies have been conducted by the U.S. Army Corp of Engineers (USACE) and Iowa Department of Transportation (DOT) to identifying a non-nuclear testing device that can perform the same functions as a nuclear density gauge. Per recommendations from the USACE, “The eGauge is the superior device for measuring wet and dry density of soil during construction operations comparing most favorably to the NDG (nuclear density gauge).” Shortfalls of the eGauge include its inability to distinguish background gamma radiation due to the decreased radioactive source necessitating background readings at least once per day and per soil type. Additionally, the eGauge does not read soil moisture with notable accuracy. Iowa DOT accepted use of the eGauge with the caveat that it will only be used to calculate wet density. Iowa DOT determined moisture content must be measured by different means (hot plate, Bunsen burner, microwave, etc.) to calculate dry density of compacted soils. The soil moisture accuracy is not considered an issue because the highly saline soils at the Grassy Mountain Facility have historically necessitated moisture content be determined by alternative means. The high salinity negatively affects the traditional nuclear density gauge from accurately acquiring moisture content to calculate dry density; thus, the dry-back process is expected to continue. The accuracy of the wet density appears to be the most important factor and the eGauge is shown to be as good as t he traditional nuclear gauge in that regard. Mr. Torstenson July 4, 2024 Page 2 We recommend the use of the Troxler eGauge 4590 (for wet density only), based on accepting ASTM D8167 as an alternative to ASTM D6938, which is defined in the Facility’s CQA Plan. A copy of ASTM D8167 Standard Test Method is also attached to this letter. It is expected that the recommended Troxler eGauge 4590 density meter will provide equivalent or improved data during construction. Sincerely, ___________________________ Gordon L. Jones, P.E. President Mr. Torstenson July 4, 2024 Page 3 References Berney, E.S., IV, Mejias-Santiago, M, and Norris, M.D. November 2016. Validation Testing of Non-Nuclear Alternatives to Measure Soil Density. ERDC/GSL TR-16-28. US Army Corps of Engineers, Engineer Research and Development Center. Retrieved from: https://troxlerlabs.com/wp-content/uploads/2023/07/USArmyEGaugeReport.pdf Serio, Melissa, March 2022. Evaluation of Non-regulated Portable Moisture Density Gauge. Iowa DOT, Construction & Materials Bureau. Retrieved from: https://publications.iowa.gov/41903/1/Evaluation%20of%20Non- regulated%20Portable%20Moisture%20Density%20Guage%20Report%2019 -SPR0- 007.pdf Designation: D8167/D8167M -18a Standard Test Method for In-Place Bulk Density of Soil and Soil-Aggregate by a Low- Activity Nuclear Method (Shallow Depth) 1 This standard is issued under the ﬁxed designation D8167/D8167M; 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* 1.1 This test method describes the procedures for measuring in-place bulk density of soil and soil-aggregate using nuclear equipment with radioactive sources (hereafter referred to simply as “gauges.”) These gauges are distinct from those described in Test Method D6938 insofar as: 1.1.1 These gauges do not contain a system (nuclear or otherwise) for the determination of the water content of the material under measurement. 1.1.2 These gauges have photon yields sufficiently low as to require the inclusion of background radiation effects on the response during normal operation. 1.1.2.1 For the devices described in Test Method D6938, the contribution of gamma rays detected from the naturally- occurring radioisotopes in most soils (hereafter referred to as “background”) compared to the contribution of gamma rays used by the device to measure in-place bulk density is typically small enough to be negligible in terms of their effect on measurement accuracy. However, for these low-activity gauges, the gamma ray yield from the gauge is low enough that the background contribution from most soils compared to the contribution of gamma gays from the gauge is no longer negligible, and changes in this background can adversely affect the accuracy of the bulk density reading. 1.1.2.2 In order to compensate for potentially differing background contribution to low-activity gauge measurements at different test sites, a background reading must be taken in conjunction with gauge measurements obtained at a given test site. This background reading is utilized in the bulk density calculation performed by the gauge with the goal of minimiz- ing these background effects on the density measurement accuracy. 1.2 For limitations see Section 5 on Interferences. 1.3 The bulk density of soil and soil-aggregate is measured by the attenuation of gamma radiation where the source is placed at a known depth up to 200 mm [8 in.] and the detector(s) remains on the surface (some gauges may reverse this orientation). 1.3.1 The bulk 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. 1.3.2 Neither the dry density nor the water content of the test sample is measured by this device. However, the results of this test can be used with the water content or water mass per unit volume value determined by alternative methods to determine the dry density of the test sample. 1.4 The gauge is calibrated to read the bulk density of soil or soil-aggregate. 1.5 All observed and calculated values shall conform to the guidelines for signiﬁcant digits and rounding established in Practice D6026. 1.5.1 For purposes of comparing, a measured or calculated value(s) with speciﬁed limits, the measured or calculated value(s) shall be rounded to the nearest decimal or signiﬁcant digits in the speciﬁed limits. 1.5.2 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 proce- dures used do not consider material variation, purpose for obtaining the data, special purpose studies, or any consider- ations for the user’s objectives; and it is common practice to increase or reduce signiﬁcant digits of reported data to com- mensurate with these considerations. It is beyond the scope of this standard to consider signiﬁcant digits used in analysis methods for engineering design. 1.6 Units—The values stated in either SI units or inch- pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non- conformance with the standard. Reporting test results in units other than SI shall not be regarded as nonconformance with this standard. 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 ofASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.08 on Special and Construction Control Tests. Current edition approved Nov. 15, 2018. Published November 2018. Originally approved in 2018. Last previous edition approved in 2018 as D8167/D8167M–18. DOI: 10.1520/D8167_D8167M–18A. *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 ' R Z Q O R D G H G 3 U L Q W H G $ F F H V V H G E \ X V H U ˚ * R U G R Q - R Q H V _ ' D W H ˚ : H G - X O Ł ⁄ - ł ˚ Ł ˛ ˚ - ˘ - Ł - ˘ responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability of regulatory limitations prior to use. NOTE 1—Nuclear density gauge manuals and reference materials, as well as the gauge displays themselves, typically refer to bulk density as “wet density” or “WD.” NOTE 2—The term “bulk density” is used throughout this standard. This term has different deﬁnitions in Terminology D653, depending on the context of its use. For this standard, however, “bulk density” refers to, as deﬁned in Terminology D653, “the total mass of partially saturated or saturated soil or rock per unit total volume.” 1.8 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. 2. Referenced Documents 2.1 ASTM Standards: 2 D653 Terminology Relating to Soil, Rock, and Contained Fluids D698 Test Methods for Laboratory Compaction Character- istics of Soil Using Standard Effort (12,400 ft-lbf/ft 3 (600 kN-m/m3)) D1557 Test Methods for Laboratory Compaction Character- istics of Soil Using Modiﬁed Effort (56,000 ft-lbf/ft 3 (2,700 kN-m/m 3)) D2216 Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass D2487 Practice for Classiﬁcation of Soils for Engineering Purposes (Uniﬁed Soil Classiﬁcation System) D2488 Practice for Description and Identiﬁcation of Soils (Visual-Manual Procedures) D3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction D4253 Test Methods for Maximum Index Density and Unit Weight of Soils Using a Vibratory Table D4254 Test Methods for Minimum Index Density and Unit Weight of Soils and Calculation of Relative Density D4643 Test Method for Determination of Water Content of Soil and Rock by Microwave Oven Heating D4718 Practice for Correction of Unit Weight and Water Content for Soils Containing Oversize Particles D4944 Test Method for Field Determination of Water (Mois- ture) Content of Soil by the Calcium Carbide Gas Pressure Tester D4959 Test Method for Determination of Water Content of Soil By Direct Heating D6026 Practice for Using Signiﬁcant Digits in Geotechnical Data D6938 Test Methods for In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth) D7013 Guide for Calibration Facility Setup for Nuclear Surface Gauges D7382 Test Methods for Determination of Maximum Dry Unit Weight and Water Content Range for Effective Compaction of Granular Soils Using a Vibrating Hammer (Withdrawn 2017) 3 D7759 Guide for Nuclear Surface Moisture and Density Gauge Calibration E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method 3. Terminology 3.1 Deﬁnitions: 3.1.1 For deﬁnitions of common technical terms used in this standard, refer to Terminology D653. 3.2 Deﬁnitions of Terms Speciﬁc to This Standard: 3.2.1 nuclear gauge, n—a device containing one or more radioactive sources used to measure certain properties of soil and soil-aggregates. 3.2.2 probe, n—aslender, elongated device, part of the gauge, that is inserted into the soil being measured by the gauge. This device may contain either a radioactive source, a radiation detection device, or both. Probes containing only a radioactive source are commonly referred to as “source rods.” 3.2.3 test count, n—the measured output of a detector for a speciﬁc type of radiation for a given test. 3.2.4 standardization count, n—the measured output of a detector taken for the purposes of evaluating gauge stability and accounting for long-term aging of the radioactive sources. This output is frequently referred to as the “standard count” as well. 3.2.5 background count, n—the counts measured by the gauge to evaluate the ambient radiation in the proximity where a test measurement is to be taken rather than the radiation emitted by the gauge itself. 3.2.6 background position, n—the orientation of the gauge source rod when the background count is acquired. 4. Signiﬁcance and Use 4.1 The test method described is useful as a rapid, nonde- structive technique for in-place measurements of bulk density of soil and soil-aggregate. Test results may be used for the determination of dry density if the water content of the soil or soil-aggregate is determined by separate means, such as those methods described in Test Methods D2216,D4643,D4944, and D4959. 4.2 The test method is used for quality control and accep- tance testing of compacted soil and soil-aggregate mixtures as used in construction and also for research and development. The nondestructive nature allows repetitive measurements at a single test location and statistical analysis of the results. 2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards volume information, refer to the standard’s Document Summary page on the ASTM website. 3 The last approved version of this historical standard is referenced on www.astm.org. D8167/D8167M - 18a 2 ' R Z Q O R D G H G 3 U L Q W H G $ F F H V V H G E \ X V H U ˚ * R U G R Q - R Q H V _ ' D W H ˚ : H G - X O Ł ⁄ - ł ˚ Ł ˛ ˚ - ˘ - Ł - ˘ 4.3 Density—The fundamental assumptions inherent in the method is that Compton scattering is the dominant interaction and that the material is homogeneous. NOTE 3—The quality of the result produced by this standard test method is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing/sampling/inspection, and the like. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors. 5. Interferences 5.1 In-Place Density Interferences: 5.1.1 Measurements may be affected by the chemical com- position of the material being tested. 5.1.2 Measurements may be affected by non-homogeneous soils and surface texture (see 10.2). Excessive voids in the prepared test surface beneath the gauge can cause density measurements that are lower than the actual soil density. Excessive use of ﬁll material to compensate for these voids may likewise cause biased density measurements. 5.1.3 The measurement volume of the gauge in a given probe orientation extends from near the tip of the probe to the detector at the surface of the in situ material under measure- ment. This volume is similar to that described by the volume bounded by an elliptic paraboloid surface. This volume varies for different depths of the probe within the material under measurement. Large particles near the probe tip may also distort the volume of measurement of the gauge. 5.1.4 Gravel particles or large voids in the source-detector path may cause higher or lower density measurements. Where lack of uniformity in the soil due to layering, aggregate or voids is suspected, the test site should be excavated and visually examined to determine whether the test material is representative of the in situ material in general and whether an oversize correction is required in accordance with Practice D4718. 5.1.5 The measured volume is approximately 0.0057 m 3 [0.20 ft 3 ] when the test depth is 150 mm [6 in.]. The actual measured volume is indeterminate and varies with the appara- tus and the density of the material. 5.1.6 Perform gauge measurements with the gauge far enough away from other apparatus containing radioactive sources to prevent interference due to radiation from the other apparatus. (See Note 4.) 5.1.7 For gauges with low source activity, variations in ambient background radiation from one test site to another may signiﬁcantly inﬂuence test results. In such instances this ambient background radiation must be measured at the test site in conjunction with the test measurement and used in the calculation of the measured bulk density. 5.1.8 The gamma radiation response for any detector is typically inﬂuenced by the environmental testing temperature. 5.1.8.1 For scintillation detectors, changing temperatures may cause variations in the resulting light output distribution from the crystal—both in magnitude and shape of the spec- trum. These variations may result in corresponding variations in the number of counted photons and, consequently, the wet density determined from the measurement. 5.1.8.2 The changes to the detector response due to tem- perature changes are compensated by various detector stabili- zation methods that compare current detector response to a standardized response and correct for energy spectrum changes accordingly. 5.1.8.3 The working temperature range of the gauge at which the aforementioned temperature variations are compen- sated is provided in the gauge speciﬁcations. In general, for a gauge using a sodium iodide scintillation detector, the working temperature range is similar to that of a nuclear gauge using Geiger-Mueller gas detectors: –10 to 70 °C [14 to 158 °F]. Please refer to the operator’s manual to ﬁnd the operating temperature range of the gauge. 5.1.8.4 For special applications where the gauge is used outside the operating temperature range, please consult the gauge manufacturer. NOTE 4—Separation of the gauge described in this standard by a distance of 9 m [30 ft] from one another, or from the gauges described in Test Method D6938, has typically proven sufficient in preventing radiation from one gauge from being detected by another gauge and potentially causing an incorrect standardization or test measurement reading. This separation can be reduced by the proper use of shielding. With regards to reﬂections from large masses or other items potentially causing incorrect standardization counts, a separation of1m[3ft]between the gauge and the mass or item in question has typically proven sufficient to prevent such reﬂections from inﬂuencing the standardization counts. 6. Apparatus 6.1 Nuclear Density Gauge—While exact details of con- struction of the apparatus may vary, the system shall consist of: 6.1.1 Gamma Source—A sealed source of high-energy gamma radiation such as cesium, cobalt, or radium. 6.1.2 Gamma Detector—Any type of gamma detector, but typically a scintillation detector or semiconductor based detec- tor. 6.2 Site Preparation Device—A plate, straightedge, or other suitable leveling tool that may be used for planing the test site to the required smoothness and guiding the drive pin to prepare a perpendicular hole. 6.3 Drive Pin—A pin of slightly larger diameter than the probe in the instrument, used to prepare a hole in the test site for inserting the probe. 6.3.1 Drive Pin Guide—A ﬁxture that keeps the drive pin perpendicular to the test site. Generally part of the site preparation device. 6.4 Hammer—Heavy enough to drive the pin to the required depth without undue distortion of the hole. 6.5 Drive Pin Extractor—Atool that may be used to remove the drive pin in a vertical direction so that the pin will not distort the hole during the extraction process. 6.6 Slide Hammer, with a Drive Pin Attached—As an alternative to 6.3 through 6.5, may also be used both to prepare a hole in the material to be tested and to extract the pin without distortion of the hole. D8167/D8167M - 18a 3 ' R Z Q O R D G H G 3 U L Q W H G $ F F H V V H G E \ X V H U ˚ * R U G R Q - R Q H V _ ' D W H ˚ : H G - X O Ł ⁄ - ł ˚ Ł ˛ ˚ - ˘ - Ł - ˘ 7. Hazards 7.1 These gauges utilize radioactive materials that may be hazardous to the health of the users unless proper precautions are taken. Users of these gauges must become familiar with applicable safety procedures and government regulations and follow these standards when using the gauge. 7.2 Effective user instructions, together with routine safety procedures, are a mandatory part of the operation and storage of these gauges. 8. Calibration 8.1 Gauge calibration shall be performed in accordance with Guides D7759 and D7013. 9. Standardization 9.1 Nuclear density gauges are subject to long-term aging of the radioactive sources, which will change the relationship between test count rates and the material bulk density. To correct for this aging effect, gauges are calibrated as a ratio of the test count rate to a reference count rate. 9.2 Standardization of the gauge must be performed at the start of each day’s use, and a record of these data must be retained for the amount of time required to ensure compliance with either 9.2.8 or 9.2.8.1, whichever is applicable. 9.2.1 Perform the standardization with the gauge far enough away from other apparatus containing radioactive sources to prevent interference due to radiation from the other apparatus. In addition, perform the standardization far enough away from large masses or other items which can affect the reference count rates due to reﬂections from these masses or items. (See Note 4.) 9.2.2 Turn on the gauge and allow for stabilization accord- ing to the manufacturer’s recommendations. 9.2.3 Prepare the site where the standardization measure- ment will be made as described in 10.2. 9.2.4 If the site where the standardization measurement will be made will also be used as a test site immediately after the standardization measurement, then make a hole perpendicular to the prepared surface using either a hammer and a drive pin or a slide hammer, using the rod guide to ensure the integrity of the hole. The hole should be a minimum of 50 mm [2 in.] deeper than the desired measurement depth of the test that follows the standardization process, and of an alignment that insertion of the probe will not cause the gauge to tilt from the plane of the prepared area. If the site where the standardization measurement will be made will not be used as a test site, then simply make a 50 mm [2 in.] hole perpendicular to the prepared surface using either a hammer and a drive pin or a slide hammer, using the rod guide to ensure the integrity of the hole. 9.2.5 Remove the hole-forming device carefully, using a drive pin extractor when needed, to prevent the distortion of the hole, damage to the surface, or loose material from falling into the hole. 9.2.6 With the gauge placed over the prepared hole and the probe in safe position, take a reading that is the duration of a normal measurement period (where a normal measurement period is typically two minutes). 9.2.7 Immediately after the preceding count is complete, lower the probe to background position, into the hole that was formed in 9.2.4, and take a two minute background count. The difference between the count acquired in 9.2.6 and this back- ground constitutes one standardization count. 9.2.8 Use the procedure recommended by the gauge manu- facturer to establish the compliance of the standard measure- ment to the accepted range. Otherwise, without speciﬁc rec- ommendations from the gauge manufacturer, use the procedure in 9.2.8.1. 9.2.8.1 If the values of the current standardization count are outside the limits set by Eq 1, repeat the standardization check. If the second standardization check satisﬁes Eq 1, the gauge is considered in satisfactory operating condition. If the second standardization check does not satisfy Eq 1, then the gauge must be removed from service until such time that the gauge can pass this standardization test. 0.98~N dc!e 2 ~ln ~2 !!t T d ~1⁄2!#N d 0 #1.02~N dc!e 2 ~ln ~2 !!t T d~1⁄2!(1) where: Td(1/2)= the half-life of the isotope that is used for the density determination in the gauge. For example, for 137Cs, the radioactive isotope most commonly used for density determination in these gauges, Td(1/2), is 11,023 days, Ndc = the density system standardization count acquired at the time of the last calibration or veriﬁcation, Nd0 = the current density system standardization count, t = the time that has elapsed between the current standardization test and the date of the last calibra- tion or veriﬁcation. The units selected for t and Td(1/2)should be consistent, that is, if Td(1/2)is expressed in days, then t should also be expressed in days. and Ndc and Nd0 are corrected for background effects as described in 11.1.1. 9.2.8.2 Example—A nuclear gauge containing a 137Cs source for density determination (half-life = 11,023 days) is calibrated on March 1 of a speciﬁc year. At the time of calibration, the density standard count was 2800 counts per minute (prescaled.) According to Eq 1 from 9.2.7, what is the allowed range of standard counts for November 1 of the same year? (1)For this example, a total of 245 days have elapsed between the date of calibration or veriﬁcation (March 1) and the date of the gauge standardization (November 1). Therefore: t 5 245□days T d ~1⁄2!5 11023□days N dc 5 2800□counts (2)According to Eq 1, therefore, the lower limit for the density standard count taken on November 1, denoted by Nd0, is: 0.98~N dc!e 2 ~ln ~2!!t T d ~1⁄2!5 0.98~2800!e 2 ~ln ~2 !!3 245 11023 5 2744e 2 0.01541 5 2702□counts (3)Likewise, the upper limit for the density standard count taken on November 1, denoted by Nd0, is: D8167/D8167M - 18a 4 ' R Z Q O R D G H G 3 U L Q W H G $ F F H V V H G E \ X V H U ˚ * R U G R Q - R Q H V _ ' D W H ˚ : H G - X O Ł ⁄ - ł ˚ Ł ˛ ˚ - ˘ - Ł - ˘ 1.02~N dc!e 2~ln ~2 !!t Td~1⁄2!5 1.02~2800!e 2 ~ln ~2 !!3 245 11023 5 2856e 2 0.01541 5 2812□counts 9.2.9 If for any reason the measured bulk density becomes suspect during the day’s use, perform another standardization count. 10. Procedure 10.1 When possible, select a test location where the gauge will be placed at least 600 mm [24.0 in.] away from any object sitting on or projecting above the surface of the test location, where the presence of this object has the potential to modify gauge response. Any time a measurement must be made at a speciﬁc location and the aforementioned clearance cannot be achieved, such as in a trench, follow the gauge manufacturer’s correction procedure(s). 10.2 Prepare the test site in the following manner: 10.2.1 Remove all loose and disturbed material and addi- tional material as necessary to expose the true surface of the material to be tested. 10.2.2 Prepare an area sufficient in size to accommodate the gauge by grading or scraping the area to a smooth condition so as to obtain maximum contact between the gauge and material being tested. 10.2.3 The depth of the maximum void beneath the gauge must not exceed 3 mm [ 1⁄8 in.]. Use either native material that does not contain gravel, or use ﬁne sand, to ﬁll the voids, and then smooth the surface with the site preparation device or other suitable tool. The depth of the ﬁller should not exceed approximately 3 mm [ 1⁄8 in.]. 10.2.4 The placement of the gauge on the surface of the material to be tested is critical to accurate density measure- ments. The optimum condition is total contact between the bottom surface of the gauge and the surface of the material being tested. The total area ﬁlled should not exceed approxi- mately 10 percent of the bottom area of the gauge. 10.3 Turn on and allow the gauge to stabilize (warm up) according to the manufacturer’s recommendations (see 9.2.2). 10.4 The Measurement Procedure: 10.4.1 When possible, select a test location where the gauge will be placed at least 600 mm [24.0 in.] away from any object sitting on or projecting above the surface of the test location, when the presence of this object has the potential to modify gauge response. Any time a measurement must be made at a speciﬁc location and the aforementioned clearance cannot be achieved, such as in a trench, follow the gauge manufacturer’s correction procedure(s). 10.4.2 Make a hole perpendicular to the prepared surface using either a hammer and a drive pin or a slide hammer, using the rod guide to ensure the integrity of the hole. The hole should be a minimum of 50 mm [2 in.] deeper than the desired measurement depth and of an alignment that insertion of the probe will not cause the gauge to tilt from the plane of the prepared area. 10.4.3 Mark the test area to allow the placement of the gauge over the test site and to align the probe to the hole. Follow the manufacturer’s recommendations. 10.4.4 Remove the hole-forming device carefully, using a drive pin extractor when needed, to prevent the distortion of the hole, damage to the surface, or loose material falling into the hole. NOTE 5—Care must be taken in the preparation of the access hole in uniform cohesionless granular soils. Measurements can be affected by damage to the density of surrounding materials when forming the hole by potentially creating air voids what would not ordinarily be in the undisturbed material. 10.4.5 Place the gauge on the material to be tested, ensuring maximum surface contact as described previously in 10.2.4. 10.4.6 Lower the probe into the hole to the desired test depth. Pull the gauge gently toward the back, or detector end, so that the back side of the probe is in intimate contact with the side of the hole in the gamma measurement path. NOTE 6—As a safety measure, it is recommended that a probe containing radioactive sources not be extended out of its shielded position prior to placing it into the test site. When possible, align the gauge to allow placing the probe directly into the test hole from the shielded position. 10.4.7 Ensure that the gauge is far enough away from other apparatus containing radioactive sources to prevent interfer- ence due to radiation from the other apparatus. (See Note 4.) 10.4.8 If the gauge requires the probe depth to be entered into the gauge or otherwise selected by the user prior to a test measurement, then set the depth selector to the same depth as the probe. 10.4.9 Secure and record one or more bulk density readings, where the duration of the reading corresponds with the desired gauge measurement precision level (see Annex A1). Read the in-place bulk density directly or determine one by use of the calibration curve or table previously established. 10.4.10 If this is the ﬁrst reading in a new job site or a new in situ material, move the source rod to background position and take a one-minute background count. 10.4.11 If desired, using a separate method or device, make a water content or water mass per unit volume measurement. Use the data collected in this manner with the bulk density measured by the nuclear gauge to determine the dry density and water content of the test site. 10.5 Oversize Particle Correction: 10.5.1 When oversize particles are present, the gauge can be rotated about the axis of the probe to obtain additional readings as a check. When there is any uncertainty as to the presence of these particles it is advisable to sample the material beneath the gauge to verify the presence and the relative proportion of the oversize particles. A rock correction can then be made for bulk density by the method in Practice D4718. 11. Calculation of Results 11.1 Determine the Bulk Density: 11.1.1 On most gauges, read the value directly in kg/m 3 [lbm/ft3]. If the bulk density reading is in test counts, determine the in-place bulk density by use of this reading and the previously established calibration curve or table for density. The dependent variable used in this calibration curve to compute the density is calculated as a quotient, where the divisor is the gauge count on the test material minus the D8167/D8167M - 18a 5 ' R Z Q O R D G H G 3 U L Q W H G $ F F H V V H G E \ X V H U ˚ * R U G R Q - R Q H V _ ' D W H ˚ : H G - X O Ł ⁄ - ł ˚ Ł ˛ ˚ - ˘ - Ł - ˘ background count on the test material, and the dividend is the safe position count minus the background count taken at standardization time. 11.1.2 Record the bulk density to the nearest 1 kg/m 3 [0.1 lbm/ft3]. 11.2 It may be desired to use the bulk density value measured by this method to compute the dry density of the soil being measured. One may use methods such as those described in Test Methods D2216,D4643,D4944, and D4959 to deter- mine the water content of the soil and compute the dry density from the water content and bulk density. 11.2.1 If one computes the dry density as described in 11.2, it may be desired to express the in-place dry density as a percentage of a laboratory density such as Test Methods D698, D1557,D4253,D4254,orD7382. This relationship can be calculated by dividing the in-place dry density by the labora- tory maximum dry density and multiplying by 100. Corrections for oversize material, if required, should be performed in accordance with Practice D4718. 12. Report: Test Data Sheet(s)/Form(s) 12.1 The methodology used to specify how data are re- corded on the test data sheet(s)/form(s), as given below, is covered in 1.6. 12.2 Record as a minimum the following general informa- tion (data): 12.2.1 Test Number or Test Identiﬁcation. 12.2.2 Location of test (for example, Station number or GPS Coordinates or other identiﬁable information). 12.2.3 Visual description and identiﬁcation of material tested. 12.2.4 Lift number or elevation or depth. 12.2.5 Name of the operator(s). 12.2.6 Make, model and serial number of the test gauge. 12.2.7 Standardization, background, and adjustment data for the date of the tests. 12.2.8 Any corrections made in the reported values and reasons for these corrections (for example, over-sized par- ticles). 12.2.9 Maximum laboratory density value in kg/m 3 or lbm/ft3, if required for these measurements. 12.3 Recording the gauge counts—and background counts, when acquired—for the purpose of verifying the integrity of the recorded data is recommended. 12.4 The sensitivity of the measurement values listed in reporting and records are described in 11.1.2. 13. Precision and Bias 4 13.1 The precision of this test method is based on an interlaboratory study ILS 1339, “Standard Test Method for In-Place Bulk Density of Soil and Soil-Aggregate by a Low- Activity Nuclear Method (Shallow Depth) and In-Place Water Mass Per Unit Volume of Soil and Soil-Aggregate by Permit- tivity Method (Shallow Depth),” conducted in 2017. Ten laboratories tested three materials with three replicate readings on each material. Every “test result” represents an individual determination. Practice E691 was followed for the design and analysis of the data; the details are given in ASTM Research Report No. D18-1024. 13.1.1 Repeatability (r)—The difference between repetitive results obtained by the same operator in a given laboratory applying the same test method with the same apparatus under constant operating conditions on identical test material within short intervals of time would in the long run, in the normal and correct operation of the test method, exceed the values in Table 1 only in one case in 20. 13.1.1.1 Repeatability can be interpreted as maximum dif- ference between two results, obtained under repeatability conditions, that is accepted as plausible due to random causes under normal and correct operation of the test method. 13.1.1.2 Repeatability limits are listed in Table 1. 13.1.2 Reproducibility (R)—The difference between two single and independent results obtained by different operators applying the same test method in different laboratories using different apparatus on identical test material would, in the long run, in the normal and correct operation of the test method, exceed the values in Table 1 only in one case in 20. 13.1.2.1 Reproducibility can be interpreted as maximum difference between two results, obtained under reproducibility conditions, that is accepted as plausible due to random causes under normal and correct operation of the test method. 13.1.2.2 Reproducibility limits are listed in Table 1. 13.1.3 The above terms (repeatability limit and reproduc- ibility limit) are used as speciﬁed in Practice E177. 4 Supporting data have been ﬁled at ASTM International Headquarters and may be obtained by requesting Research Report RR:D18-1024. ContactASTM Customer Service at service@astm.org. TABLE 1 Results of Statistical Analysis (Bulk Density) Material Average kg/m 3 or [lbm/ ft3] Repeatability Standard Deviation kg/m 3 or [lbm/ ft3]A Reproducibility Standard Deviation kg/m 3 or [lbm/ ft3]A Repeatability Limit kg/m3 or [lbm/ft 3]B Reproducibility Limit kg/m3 or [lbm/ft 3]B x¯SrSR rR 1 1933 [120.6] 4.3 [0.3] 10 [0.6] 12 [0.8] 29 [1.8] 2 1949 [121.6] 5.9 [0.4] 10 [0.6] 16 [1.0] 28 [1.8] 3 2224 [138.9] 7.1 [0.4] 13 [0.8] 20 [1.2] 36 [2.2] AThe number of signiﬁcant digits and decimal places presented are representative of the input data. In accordance with Practice D6026, the standard deviation and acceptable range of results cannot have more decimal places than the input data. BAcceptable range of two results is referred to as the d2s limit. It is calculated as 1.960=2·1s, as deﬁned by Practice E177. The difference between two properly conducted tests should not exceed this limit. The number of signiﬁcant digits and decimal places presented are equal to that prescribed by this standard or Practice D6026. In addition, the presented value can have the same number of decimal places as the standard deviation, even if that result has more signiﬁcant digits than the standard deviation. D8167/D8167M - 18a 6 ' R Z Q O R D G H G 3 U L Q W H G $ F F H V V H G E \ X V H U ˚ * R U G R Q - R Q H V _ ' D W H ˚ : H G - X O Ł ⁄ - ł ˚ Ł ˛ ˚ - ˘ - Ł - ˘ 13.1.4 Any judgment in accordance with statements 13.1.1 and 13.1.2 would have an approximate 95 % probability of being correct. 13.2 Bias—At the time of the study, there was no accepted reference material suitable for determining the bias for this test method, therefore no statement on bias is being made. 13.3 The precision statement was determined through sta- tistical examination of three replicate results, from ten laboratories, on three materials. These three materials were the following, as listed in Table 1, and described in accordance with Practices D2487 and D2488: Material 1: SC—Coarse graded clayey sand with ﬁnes, 1 % gravel, 2 % coarse sand, 28 % medium sand, 44 % ﬁne sand, 25 % ﬁnes, liquid limit = 32, plastic index = 13 Material 2: SC—Coarse graded clayey sand with ﬁnes, 2 % gravel, 6 % coarse sand, 24 % medium sand, 27 % ﬁne sand, 41 % ﬁnes, liquid limit = 42, plastic index = 20 Material 3: Poorly graded gravel with silt, 52 % gravel, 13 % coarse sand, 15 % medium sand,13 % ﬁne sand, 7% ﬁnes 13.4 To judge the equivalency of two test results, it is recommended to choose the soil type closest in characteristics to the test soil. 14. Keywords 14.1 acceptance testing; bulk density; compaction test; con- struction control; dry density; ﬁeld density; in-place density; low-activity; nuclear gauge; nuclear methods; quality control; soil density; wet density ANNEX (Mandatory Information) A1. GAUGE PRECISION A1.1 Gauge precision is deﬁned as the change in density measured by the gauge that occurs corresponding to a one standard deviation change in the test count due to the random decay of the radioactive source. The density of the material and time period of the test count must be stated. A1.2 Calculate using the methods in either A1.4 or A1.5. For bulk density, use a material having a density of 2000 6 80 kg/m3 [125.0 6 5.0 lbm/ft 3]. A1.3 Using the manufacturer recommended measurement time, a typical value of gauge precision is <5 kg/m 3 [0.3 lbm/ft3] for direct transmission measured at a 15 cm [6 in.] depth. A1.4 Gauge Precision—Slope Method A1.4.1 Determine the gauge precision of the system,P, from the slope of the calibration curve,S, and the standard deviation,σ, of the signals (detected gamma rays) in counts per minute (cpm), as follows: P 5 σ S where: P = precision σ = standard deviation, cpm S = slope, cpm/kg/m 3 [cpm/lbm/ft3] NOTE A1.1—Displayed gauge test counts may be scaled. Contact the manufacturer to obtain the appropriate pre-scale factor. A1.5 Gauge Precision—Repetitive Method A1.5.1 Determine the standard deviation of a minimum of 20 repetitive readings at the typical measurement time, without moving the gauge between readings. Calculate the standard deviation of the resulting readings. This is the gauge precision. D8167/D8167M - 18a 7 ' R Z Q O R D G H G 3 U L Q W H G $ F F H V V H G E \ X V H U ˚ * R U G R Q - R Q H V _ ' D W H ˚ : H G - X O Ł ⁄ - ł ˚ Ł ˛ ˚ - ˘ - Ł - ˘ APPENDIX (Nonmandatory Information) X1. DATA SHEETS/FORMS X1.1 See Fig. X1.1. FIG. X1.1 Example Data Form D8167/D8167M - 18a 8 ' R Z Q O R D G H G 3 U L Q W H G $ F F H V V H G E \ X V H U ˚ * R U G R Q - R Q H V _ ' D W H ˚ : H G - X O Ł ⁄ - ł ˚ Ł ˛ ˚ - ˘ - Ł - ˘ SUMMARY OF CHANGES In accordance with Committee D18 policy, this section identiﬁes the location of changes to this standard since the last edition (2018) that may impact the use of this standard. (November 15, 2018) (1)The description of the quantities “ln(2)” and “e” are omitted from 9.2.8.1. ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility. This standard is subject to revision at any time by the responsible technical committee and must be reviewed every ﬁve years and if not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards, at the address shown below. This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the above address or at 610-832-9585 (phone), 610-832-9555 (fax), or service@astm.org (e-mail); or through the ASTM website (www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http://www.copyright.com/ D8167/D8167M - 18a 9 ' R Z Q O R D G H G 3 U L Q W H G $ F F H V V H G E \ X V H U ˚ * R U G R Q - R Q H V _ ' D W H ˚ : H G - X O Ł ⁄ - ł ˚ Ł ˛ ˚ - ˘ - Ł - ˘ Exempt from the Hassles of Licensing Maintaining a radioactive materials license can be complicated and time consuming for owners of “Specifically Licensed” gauges. In the United States, the EGauge is exempt from the radioactive materials license: no special training classes for operators, no TLD badges, no special shipping documents, and no reciprocity needed to use it in other states. Easy to Use The operation of the Model 4590 is similar to that of the traditional Troxler nuclear density gauges and therefore, the experienced operator can use the gauge with little additional training. Reliable and Repeatable Density Results Data collected by multiple agencies show excellent correlation between the EGauge and Troxler’s Model 3440 Density Gauge (R2 values ranged from 0.93 to 0.98). EGauge repeatability is also equal to that of the current density gauges as listed in the applicable ASTM specification (0.3 lb/ft3 (4.8 kg/m3)). Complete with Moisture Probe The Troxler Model 6760 Moisture Probe is provided with each EGauge. The electromagnetic probe measures the moisture of the soil in the same prepared hole that is used for the density measurement. Bluetooth technology enables the probe to communicate the moisture data to the EGauge allowing the gauge to display complete results. The EGauge also accepts moisture data using the keypad if another method is used. A field offset is generally required to assure realiable moisture results when using electromagnetic technology. Troxler EGauge Model 4590 Nuclear Soil Density Gauge A Nuclear Density Gauge Exempt from NRC Licensing! Troxler, the industry leader in nuclear density gauges, now offers a license exempt* option for soil quality control testing! The EGauge uses proven nuclear technology for density measurements unlike other non-licensed density measurement devices. • Accurate and realible readings • As easy to use as Troxler’s current gauges • Meets ASTM D8167 EGauge Measurement Specifications Parameters at 6 inch (150 mm) Depth Parameters at 135 lb/ft3 (2163 kg/m3) Sample Density Measurement Time = 2 min; Background Time = 1 min Precision Repeatability (1-standard deviation) 0.3 lb/ft3 (4.8 kg/m3) Reproducibility (1-standard deviation)0.5 lb/ft3 (8.0 kg/m3)1 Composition Error 0 lbs/ft3 (0 kg/m3) Mechanical Specifications EGauge Size (H x L x W)24.6” x 15.4” x 9.2” 625mm x 391mm x 234mm Moisture Probe Size (H x L x W)8.2” x 13.6” x 5.6” 208mm x 346mm x 142mm Case Dimensions (H x L x W)31.3” x 20.4” x 15.5” 795mm x 518mm x 393mm Weight 35 lbs (13.8 kg) Shipping Weight 83 lbs (38 kg) Operating Temperature 0° to 50° C (32° to 122° F) Storage Temperature -18° to 60° C (0° to 140° F) Electrical Specifications Main Power Source NiMH rechargeable batteries Backup Power Source 5 AA alkaline batteries Charge Source 12 V DC, 2A Battery Recharge Time 3 hours maximum, (may be charged incrementally without damaging the batteries) Time Before Automatic Shutdown 5 hours of inactivity Additional Features and Options • Easy to Read Display – easy to read enlarged LCD screen with back-lighting for viewing in low light conditions. • Automatic Depth Mode – detects the source rod depth during each measurement. • Data Storage and Output – stores up to 1000 test readings under multiple projects for later recall or downloading. • Auto-Store Function – when enabled automatically stores sample data under the active project. • USB Port – access for outputting stored data to a printer or removable storage “thumb drive.” • GPS – records GPS information with each measurement with Wide Area Augmentation System (WAAS) capabilities for better accuracy. Model 4590 Soil Density Gauge *Exempt in the United States as determined by the NRC. 1 Reproducibility as measured is consistent with that stated in ASTM-D6938-10 Each EGauge equipped with a Model 6760 Moisture Probe 3008 E. Cornwallis RoadResearch Triangle Park, NC 277091-877-TROXLER (1-877-876-9537)1-919-549-8661 (International)www.troxlerlabs.com Information provided herein is based on test data believed to be reliable. In as much as Troxler Electronic Laboratories, Inc. has no control over the manner in which others may use this information, it does not guarantee the results to be obtained. In addition, Troxler does not make any express or implied warranty of merchantability or fitness for a particular purpose other than that for which the equipment is originally intended. Made in USA ER D C /GS L TR -16 -28 Validation Testing of Non-Nuclear Alternatives to Measuring Soil Density Ge o t e c h n i c a l a n d S t r u c t u r e s La b o r a t o r y Ernest S. Berney IV, Mariely Mejías-Santiago, and Matthew D. Norris November 2016 Approved for public release; distribution is unlimited. The U.S. Army Engineer Research and Development Center (ERDC) solves the nation’s toughest engineering and environmental challenges. ERDC develops innovative solutions in civil and military engineering, geospatial sciences, water resources, and environmental sciences for the Army, the Department of Defense, civilian agencies, and our nation’s public good. Find out more at www.erdc.usace.army.mil. To search for other technical reports published by ERDC, visit the ERDC online library at http://acwc.sdp.sirsi.net/client/default. ERDC/GSL TR-16 -28 November 2016 Validation Testing of Non-Nuclear Alternatives to Measuring Soil Density Ernest S. Berney IV, Mariely Mejías-Santiago, and Matthew D. Norris Geotechnical and Structures Laboratory U.S. Army Engineer Research and Development Center 3909 Hall Ferry Road Vicksburg, MS 39180 Final report Approved for public release; distribution is unlimited. Prepared for Headquarters, Air Force Civil Engineering Center Tyndall Air Force Base, FL 32403-5319 Under Project 447413 ERDC/GSL TR-16-28 ii Abstract During 2015, researchers with the U.S. Army Engineer Research and Development Center (ERDC) validated the effectiveness of the TransTech Combined Asphalt Soil Evaluator (CASE) and the Troxler eGauge as suitable replacements for nuclear density gauge (NDG) technology. Comparisons of soil dry density and moisture content were made between the gauges for six distinct soil types at varying densities and moisture contents. The CASE unit was calibrated using the Sand Cone and hot-plate moisture content prior to its correlation to the NDG; the eGauge was used in its shipped configuration without calibration. Results of both devices were compared to the NDG and core samples to capture asphalt density. Full-scale test sections were constructed for the soil evaluations ranging from crushed limestone to fat clays. Results showed that wet and dry densities obtained with the eGauge very closely matched those of the NDG, but the accuracy of the measured moisture contents was lower. The CASE unit’s calibrated accuracy to the NDG moisture content was excellent, but its wet and dry density accuracies were much lower than the eGauge. Based on the ERDC findings, the eGauge is recommended as the best replacement for the NDG for wet/dry density measurements and requires no calibration or transport/licensing restrictions. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR. ERDC/GSL TR-16-28 iii Contents Abstract .................................................................................................................................... ii Figures and Tables ................................................................................................................... v Preface .................................................................................................................................... vii Unit Conversion Factors .......................................................................................................viii 1 Introduction ...................................................................................................................... 1 1.1 Background ........................................................................................................ 1 1.2 Objectives ........................................................................................................... 2 1.3 Scope .................................................................................................................. 3 2 Materials and Instruments ............................................................................................. 4 2.1 Soils .................................................................................................................... 4 2.2 Instruments ........................................................................................................ 4 2.2.1 Nuclear moisture-density gauge ................................................................................ 6 2.2.2 CASE unit ..................................................................................................................... 7 2.2.3 EGauge ........................................................................................................................ 9 2.2.4 Sand cone.................................................................................................................. 10 2.2.5 Hot plate .................................................................................................................... 11 2.2.6 Laboratory oven ........................................................................................................ 12 3 Experimental Procedures.............................................................................................. 13 3.1 Soil test section .............................................................................................. 13 3.1.1 Test strip construction .............................................................................................. 13 3.1.2 Test procedures ........................................................................................................ 15 3.1.3 Internal gauge calibration ........................................................................................ 20 3.2 Asphalt test section ......................................................................................... 21 3.2.1 Test procedures ........................................................................................................ 21 3.2.2 Gauge validation ....................................................................................................... 23 4 Data Analysis and Results ............................................................................................ 25 4.1 Soil test section .............................................................................................. 25 4.1.1 Range of soil conditions evaluated .......................................................................... 25 4.1.2 Hot plate moisture correlation to laboratory oven dried procedure ....................... 26 4.1.3 CASE calibration ........................................................................................................ 27 4.1.4 eGauge calibration .................................................................................................... 30 4.1.5 CASE and eGauge correlations to NDG ................................................................... 31 4.1.6 Summary of performance ......................................................................................... 38 4.2 Asphalt test section ........................................................................................ 40 4.2.1 Summary of performance ......................................................................................... 40 4.2.2 CASE and eGauge correlations to NDG and core samples ..................................... 40 ERDC/GSL TR-16-28 iv 5 Conclusions and Recommendations ........................................................................... 43 5.1 Conclusions ..................................................................................................... 43 5.1.1 Soil density ................................................................................................................ 44 5.1.2 Moisture content ....................................................................................................... 44 5.1.3 Asphalt density .......................................................................................................... 44 5.2 Recommendations ......................................................................................... 44 5.2.1 Soil density and moisture content ........................................................................... 45 5.2.2 Asphalt density .......................................................................................................... 45 5.3 Areas for future study ..................................................................................... 45 References ............................................................................................................................. 47 Appendix A: Soil Characterization Data ............................................................................. 49 Appendix B: Gauge Comparison Data ................................................................................ 61 Report Documentation Page ERDC/GSL TR-16-28 v Figures and Tables Figures Figure 1. Nuclear moisture-density gauge. ................................................................................ 6 Figure 2. Combined Asphalt and Soil Evaluator (CASE). .......................................................... 8 Figure 3. Configuration of the CASE non-contacting sensor. ................................................... 8 Figure 4. Cloverleaf pattern of readings of the non-nuclear gauges. ..................................... 9 Figure 5. Troxler EGauge with Moisture Monitoring Probe. .................................................... 10 Figure 6. Sand cone density apparatus and accessories. ..................................................... 11 Figure 7. Hot plate, scale, and accessories used to determine soil moisture content. ......................................................................................................................................... 12 Figure 8. Placing soil to build a testbed using a) dump truck and b) skid steer. ................ 14 Figure 9. Soil compaction equipment: a) smooth drum roller and b) rubber tire compactor. .................................................................................................................................... 14 Figure 10. Use of plastic sheet on test strip to prevent soil adhering to the drum. ............ 15 Figure 11. Typical test item layout. ............................................................................................ 16 Figure 12. Typical instrument layout. ........................................................................................ 16 Figure 13. Testing of sand cone density following CASE, NDG, and eGauge measurements and testing of hot plate moisture content inside red ring. ......................... 17 Figure 14. Posttest locations of sand cone and hot plate samples following testing on limestone test section. .............................................................................................. 17 Figure 15. Cloverleaf pattern used for precision evaluation of CASE unit. .......................... 18 Figure 16. Driving of the nuclear gauge compaction rod for NDG and eGauge testing. ........................................................................................................................................... 19 Figure 17. NDG testing alongside the CASE unit. .................................................................... 19 Figure 18. eGauge wet density measurement with rod at 6-in. depth. ................................ 20 Figure 19. Insertion of the moisture probe following density eGauge testing. ................... 20 Figure 20. eGauge placed on rough-textured (RT) asphalt section. ..................................... 22 Figure 21. Smooth textured (ST) asphalt section (note the transition to RT at top of photo). ....................................................................................................................................... 22 Figure 22. Deep (DP) asphalt test section with pencil shown for thickness scale. ............ 23 Figure 23. Use of a combihammer to drill holes in asphalt for density probe insertion. ....................................................................................................................................... 23 Figure 24. Illustration of core separation to obtain densities at each 2-in. thickness. ...................................................................................................................................... 24 Figure 25. Moisture-density range tested for each soil type.................................................. 26 Figure 26. Comparison of hot plate versus oven dried moisture content techniques. ................................................................................................................................... 27 Figure 27. Comparison of wet density between sand cone and NDG. ................................. 28 ERDC/GSL TR-16-28 vi Figure 28. Comparison of dry density between sand cone and NDG. ................................. 28 Figure 29. Wet density differential for CASE gauge during calibration. ............................... 29 Figure 30. Moisture content differential for the CASE gauge during calibration. ............... 30 Figure 31. Dry density differential for the CASE gauge during calibration. .......................... 30 Figure 32. Correlation of eGauge density to NDG. .................................................................. 32 Figure 33. Correlation of CASE density to NDG. ...................................................................... 32 Figure 34. Correlation of eGauge moisture content to NDG/Oven. ...................................... 33 Figure 35. Correlation of CASE moisture content to NDG/Oven. .......................................... 33 Figure 36. Comparison of density between eGauge and CASE to the NDG at both high (HI) and low (LO) compaction efforts. ............................................................................... 34 Figure 37. Comparison of dry density between CASE and eGauge versus NDG by soil type. ........................................................................................................................................ 35 Figure 38. Comparison of wet density between CASE and eGauge versus NDG by soil type. ........................................................................................................................................ 36 Figure 39. Density correlation by soil type between eGauge and CASE to the NDG. .............................................................................................................................................. 37 Figure 40. Density differential between compaction efforts by soil type for each density test procedure. ............................................................................................................... 38 Figure 41. Average deviation of asphalt bulk density between NDG, CASE, and eGauge versus core samples. .................................................................................................... 41 Figure 42. Comparison of AVERAGE asphalt bulk density versus NDG and eGauge for all depths tested. .................................................................................................................... 42 Figure 43. Summary data from validation study for each device. ........................................ 43 Tables Table 1. Soil properties. ................................................................................................................ 5 Table 2. List of instruments used in this evaluation. ................................................................ 5 Table 3. Moisture levels used to prepare each soil for testing. ............................................. 13 Table 4. Range of relative density and moisture content achieved during construction. ................................................................................................................................. 25 Table 5. Average asphalt density readings for the tested devices. ....................................... 40 Table 6. Coefficient of determination between each test device and the core samples. ........................................................................................................................................ 42 ERDC/GSL TR-16-28 vii Preface This report was prepared for Headquarters, Air Force Civil Engineering Center as part of the Air Force Non-Nuclear Density Project 447413. Jeb S. Tingle was the program manager of the Air Force project. This work was performed by the Airfields and Pavements Branch (APB) and the Concrete and Materials Branch (CMB), Engineering Systems and Materials Division (ESMD), U.S. Army Engineer Research and Development Center, Geotechnical and Structures Laboratory (ERDC-GSL). At the time of publication, Dr. Timothy W. Rushing was Chief, APB; Christopher M. Moore was Chief, CMB; Gordon W. McMahon was Chief, ESMD; and Pamela G. Kinnebrew was Technical Director for Military Engineering. The Deputy Director of ERDC-GSL was Dr. William P. Grogan, and the Director was Bartley P. Durst. COL Bryan S. Green was the Commander of ERDC, and Dr. Jeffery P. Holland was Director. ERDC/GSL TR-16-28 viii Unit Conversion Factors Multiply By To Obtain cubic yards 0.7645549 cubic meters feet 0.3048 meters inches 0.0254 meters pounds (force) 4.448222 newtons pounds (force) per foot 14.59390 newtons per meter pounds (force) per square foot 47.88026 pascals pounds (force) per square inch 6.894757 kilopascals pounds (mass) per cubic foot 16.01846 kilograms per cubic meter square feet 0.09290304 square meters tons (force) 8,896.443 newtons ERDC/GSL TR-16-28 1 1 Introduction 1.1 Background The U.S. military has identified the need for eliminating the use of nuclear density gauges (NDG) to measure soil moisture and density in the field because of the restrictive requirements for the gauge’s transport, use, and storage associated with these instruments containing radioactive materials Cesium and Americium. The military is actively looking for an alternative replacement for use by all of its branches. The preference for the U.S. Air Force is a single instrument that provides asphalt density, soil density, and moisture without licensing of radioactive materials and personnel and has a comparable accuracy to the NDG. Various studies were conducted at the U.S. Army Engineer Research and Development Center (ERDC) to evaluate different options to replace the NDG. Berney et al. (2013) evaluated a variety of non-nuclear devices for measuring soil density and moisture content in the field. Results showed that the electrical-impedance-based soil density gauge (SDG) by TransTech was the most accurate and precise device measuring soil density compared to the NDG, but only when a field correction factor was applied. A follow-up study on the SDG was conducted by Mejías-Santiago et al. (2013) to collect data for 16 different types of fine-grained soils in order to expand the SDG’s capability in fine-grained soils. Results from that study confirmed the SDG’s need for a field calibration to provide accurate moisture and density measurements comparable to the NDG. This study also tested another non-nuclear gauge, TransTech’s Combined Asphalt and Soil Evaluator (CASE) but only collected data for database development, since at the time of the study it was only in a prototype configuration. The CASE is an electrical impedance-based gauge based on the SDG platform that can provide both asphalt and soil density along with moisture measurements in a single gauge. The electromagnetic characteristics of the CASE are sufficiently different from the current SDG, that it requires a complete characterization for soils and empirical algorithms that are developed to be fully compliant with the range of soils of interest to the Air Force. Following incorporation of the prior study’s soil database into the CASE software, Berney et al. (2014) conducted a field validation study on the ERDC/GSL TR-16-28 2 performance of the CASE alongside the SDG. The purpose was to verify the accuracy and precision of the CASE in measuring soil density and water content compared to the NDG in a one-to-one setting. Further, the CASE was evaluated to verify its precision and accuracy in measuring asphalt density. The CASE device almost performed as well as the SDG, but like the SDG, it lacked the ability to measure small density changes within a given soil type. The Troxler eGauge, a low radioactive source gauge, was introduced in the spring of 2015 and prompted the need for a final validation study between its performance and the CASE as the leading candidates for the Air Force to replace the NDG. This report describes the materials, testing procedures, and results of the validation of the CASE and the eGauge to provide Air Force guidance for future equipment procurement. 1.2 Objectives The objectives of this validation study included: • Collecting wet and dry density measurements using the CASE and the eGauge from test sections constructed from six different soil types at varying densities to compare their accuracy to the data from the NDG and the sand-cone techniques. • Collecting moisture content measurements using the CASE and the eGauge from test sections constructed from six different soil types at varying moisture contents to compare their accuracy to data from the NDG and the oven-dried techniques. • Comparing the ability of a hot plate to adequately capture moisture as compared to the oven-dried methodology. This is a companion study to that discussed in Berney et al. (2013). • Conducting tests on varying asphalt test sections using the CASE and the eGauge to measure asphalt density with depth and to compare their accuracy to the data from the NDG and core samples at varying thicknesses. • Summarizing the study’s results and recommending the best device for replacing the NDG for measuring moisture and density for construction quality control. ERDC/GSL TR-16-28 3 1.3 Scope This study consisted of evaluating the two functions of the CASE and the eGauge (i.e., 1) soil density and water content measurements and 2) asphalt density measurements). The CASE and eGauge were evaluated by collecting instrument readings of wet density and moisture content on test sections constructed from six different soil classifications. Standard laboratory tests were conducted prior to the evaluation to determine the engineering properties of the soils, such as grain-size distribution, plasticity characteristics, and compaction properties. The maximum dry density and optimum moisture content (OMC) of each soil were used for construction quality control purposes. Each soil was prepared in the field at two moisture levels, ideally one on the dry side of OMC and the other on the wet side of OMC, for a total of 12 test items. Each test item had final areal compacted dimensions of 16 ft by 8 ft and a thickness of at least 12 in. Each test item was tested at two levels of compaction, with data acquisition occurring between various passes of the compaction roller. Electronic gauge readings were obtained at each compaction level. Density and moisture readings were obtained at three different locations within each test item with two CASE units and one eGauge. For comparison, NDG density and moisture readings as well as soil samples for moisture content determination for both the oven and hot-plate procedures were collected at each test location. Additionally, sand-cone tests for wet density were performed to compare the electronic and nuclear density measurements to a reference standard. The asphalt function of the CASE and eGauge were evaluated by collecting measurements of asphalt density on three existing test sections at ERDC. All sections were conventional hot-mix asphalt (HMA). Data were collected at the pavement surface to evaluate backscatter readings between the NDG and CASE and at 2-in., 4-in., and 6-in. depths and to evaluate the down- hole rod measurements between the NDG and the eGauge. All of the collected data were analyzed to determine the ability of the CASE and the eGauge to adequately measure soil density and moisture content as compared to the NDG and their ability to measure asphalt pavement density. ERDC/GSL TR-16-28 4 2 Materials and Instruments 2.1 Soils Six different soil types ranging from fine-grained to coarse-grained were used for this study in order to provide a wide range of soil properties for validating the effectiveness of the devices in measuring soil density and moisture content. The Unified Soil Classification System (USCS; ASTM International 2011) soil types included high-plasticity clay (CH), low- plasticity clay (CL), clayey sand (SC), clayey-sand with gravel (SC), blended clayey sand (SC), and crushed limestone (GW-GC). While three SC soils were used in the study, only one was intended to be an SC, while the other two were closer to another desired gradation. The clayey-sand with gravel was intended to be a clayey-gravel (GC) soil but had 8 percent more sand than gravel (Table 1). The blended clayey sand was intended to be a silty- sand (SM), but the silt material used in this blend had slightly more plasticity than a true silt (ML) (silt) soil. Standard laboratory tests were performed at the ERDC Materials Testing Center (MTC) to determine basic geotechnical properties of the soils. Tests conducted on each soil included standard grain-size distribution (ASTM International 2006) with hydrometer analysis (ASTM International 2007c) for dissemination of silt and clay fractions, Atterberg limits (ASTM International 2010c) including liquid limit (LL), plastic limit (PL), and plasticity index (PI), Unified Soil Classification (USCS; ASTM International 2011), and modified proctor compaction (ASTM International 2012c) to determine optimum moisture content (OMC) and maximum dry density (MDD). Details of these test results are in Appendix A. A summary of these properties is shown in Table 1. These properties were used as the initial input data for the CASE and for test section construction purposes. The OMC was used to determine the two different moisture levels for compaction of each soil, and the MDD was used during construction to determine the different compaction levels for data collection. 2.2 Instruments The list of instruments and methods used in this study is in Table 2; the following sections describe each instrument or method in more detail. ERDC/GSL TR-16-28 5 Table 1. Soil properties. Soil ID USCS Classification Atterberg Limits Grain size (% by weight) Cu Cc MDD (pcf) OMC (%) LL PL PI Fines Sand Gravel High Plasticity Clay Clay (CH) Gray 81 23 58 95.6 4.4 0 - - 104.3 22.4 Low Plasticity Clay Clay (CL) Brown 35 22 13 97.4 2.6 0 - - 118.1 13.7 Red Clayey Sand Clayey Sand (SC), Reddish Brown 19 13 6 34.5 65.4 0 - - 119.8 12.5 Clay-Gravel Clayey Sand (SC), with Gravel; Reddish Brown 25 13 12 14.7 46.4 38.9 1714 8.1 133.1 7.4 Blended Clayey Sand Clayey Sand (SC), Brown 29 19 10 19.1 77.5 0 22.2 8.2 134.8 7.4 Limestone Gravel (GW -GC), with Silty Clay and Sand; Gray 20 14 6 5.7 21.6 72.7 24.4 2.4 145.7 4.7 Cu = Coefficient of uniformity Cc = Coefficient of curvature Table 2. List of instruments used in this evaluation. Instrument Standard Method Description Output Model 3430 Roadreader™ ASTM D6938 Nuclear Moisture- Density Gauge • Wet and Dry Density • % Moisture Content • % Voids • % Compaction CASE Not available Combined Asphalt and Soil Evaluator • Wet and Dry Density • % Moisture Content • % Compaction EGauge ASTM D7830 License Exempt Soil Density Gauge with Moisture Monitoring Probe • Wet and Dry Density • % Moisture pcf (from probe) • % Voids • % Compaction Sand Cone ASTM D1556 Density Determination • Wet Density Hot Plate ASTM D4959 Portable electric stove • Moisture Content Laboratory Oven ASTM D2216 Reference standard • Moisture Content ERDC/GSL TR-16-28 6 2.2.1 Nuclear moisture-density gauge The Troxler Model 3430 Roadreader™ nuclear moisture-density gauge, shown in Figure 1, was used for this evaluation. This gauge uses the interaction of gamma radiation with matter to measure density through direct transmission or backscatter. It determines the density of a material by counting the number of photons emitted by a cesium-137 source that are read by the detector tubes in the gauge base. In direct transmission, the source rod extends through the base of the gauge into a predrilled hole to position the source at the desired depth, a maximum of 12-in. deep. Photons from the source travel through the material in the test area, collide with electrons present in the material, and reach the photon detectors in the gauge. During a backscatter measurement, the source is lowered near the surface of the test material in the same plane as the photon detectors. The gamma photons that enter the test material must be scattered at least once to reach the detectors in the gauge. Photons emitted from the source penetrate the test material, and the scattered photons are measured by the detectors. A backscatter reading measures material from the surface to a depth of approximately 4 in. (Troxler Electronic Laboratories, Inc. 2016). Figure 1. Nuclear moisture-density gauge. A material with a high density increases the number of collisions between the gamma photons and the electrons present in the material. Therefore, the number of photons reaching the detector tubes is reduced. Hence, the ERDC/GSL TR-16-28 7 lower the number of photons reaching the detector tubes, the higher the material density. The opposite is true for material with a lower density; fewer collisions occur between the gamma photons and electrons present in the material. More photons will reach the detector tubes, increasing the density count. A microprocessor in the gauge converts these counts into a density reading (Troxler Electronic Laboratories, Inc. 2016). The moisture determination occurs in much the same way as the backscatter density reading. The Americium-241: Beryllium source is located inside of the gauge base. Fast neutrons from this source enter the test material and are slowed by collisions with hydrogen atoms present in the material. The helium 3 detector in the gauge base counts the number of thermalized (slowed) neutrons. This number (known as the moisture count) is directly related to the amount of moisture in the tested area (Troxler Electronic Laboratories, Inc. 2016). The NDG was used according to ASTM D6938 (ASTM International 2010a) with a rod driven 6 in. into the ground to obtain moisture content and wet density. 2.2.2 CASE unit The Combination Asphalt and Soil Evaluator (CASE) (Figure 2) is used to measure density of asphalt and the density and moisture content of typical construction soils using a multiple concentric ring electrode array configuration (ASTM International 2013). In soil mode, the device uses electrical impedance spectroscopy (EIS) to obtain soil density and moisture content readings non-destructively. As shown in the diagram in Figure 3, the non-contacting sensor in the CASE consists of two rings, a central ring and an outer ring. The central transmit ring injects an electric field into the soil, and the response is received by the outer sensing ring. The density, or compaction level, is measured by the response of the CASE’s electrical sensing field to changes in electrical impedance of the material matrix. Since the dielectric constant of air is much lower than that of the other soil constituents, the combined dielectric constant increases as compaction increases, because the percentage of air in the soil matrix decreases. The CASE measures the electromagnetic impedance properties of soil over several frequencies. Using the spectroscopy of the measured impedance over the frequency range, the CASE unit calculates the soil compaction properties (wet density and water content) without the typical soil information, such as grain-size properties, Atterberg limits, etc. The CASE does require a wet density offset, either from a sand cone or another secondary device. For the calculation of the soil’s wet density and ERDC/GSL TR-16-28 8 water content, the CASE unit uses the measured susceptance and resistance between 5 MHz and 25 MHz, respectively. The CASE requires collection of five discrete data points in the cloverleaf pattern shown in Figure 4 for averaging density measurements. The CASE is equipped with a touch screen, a graphical menu interface, and Global Positioning System (GPS). Figure 2. Combined Asphalt and Soil Evaluator (CASE). Figure 3. Configuration of the CASE non-contacting sensor. ERDC/GSL TR-16-28 9 Figure 4. Cloverleaf pattern of readings of the non-nuclear gauges. In asphalt mode, the outer ring is removed, and the unit operates at a single frequency to determine the density based on the measured impedance (susceptance), a factory calibration, and user inputs of aggregate size and the maximum theoretical density (MTD). This capability is identical to the company’s own Pavement Quality Indicator (PQI) technology. The Transtech PQI 301 instrument is used as a standard non-nuclear test device in asphalt construction evaluation. Research has shown that its performance compares well with the nuclear density gauge (Zhuang 2011). 2.2.3 EGauge The Troxler EGauge (Figure 5) is a new license exempt soil density gauge. The technology of the traditional nuclear density gauge is still utilized in this new model for the measurement of wet density using a Cesium-source tipped rod to produce gamma photons. This device has a larger and more insulated detector plate to mask low level background radiation while still maintaining sensitivity to capture the low photon emittance from the small Cesium source. Licensing is not required with the eGauge, because the Cesium source emits radiation below the Nuclear Regulatory Commission’s human safety limits and therefore, the radiation dose to the operator poses no danger. The gauge by itself only measures wet soil density; however, it has the capability to measure moisture content electronically through a secondary probe that is attached by a cable to the main body and is inserted into the ground using the same or different hole 5 4 1 3 2 ERDC/GSL TR-16-28 10 drilled for the density source rod. This gauge does not have the backscatter option of the NDG, as it requires penetration of the probe into the ground to measure density. This new gauge features a GPS, a USB port, and backlit display. Figure 5. Troxler EGauge with Moisture Monitoring Probe. 2.2.4 Sand cone The sand cone test was used in this study as the reference standard for comparing the effectiveness of the non-nuclear devices in measuring in place soil density. The sand cone density test is a volume replacement test that determines the wet density of a soil. Density is determined by the quotient of soil mass removed from a hole divided by the volume of the hole. The volume of the hole created is indirectly measured by the mass of sand used to fill the hole, with the assumption that the sand fills the hole with a known, uniform density (Sebesta et al. 2006). The sand cone replacement test was conducted according to ASTM D1556 (ASTM International 2007b). Clay was used to seal the inner ring of the sand cone plate to minimize sand grains being trapped beneath the plate. A #20-#30 grade Ottawa sand was used as the uniform sand. Three sand cone devices were used during testing to expedite the process. Each sand cone bottle was water and sand calibrated prior to the start of the exercise, but no further calibration checks were conducted after the testing began. A ERDC/GSL TR-16-28 11 field scale accurate to ±0.5 g determined the mass of soil and sand. A surface calibration was performed on every hole dug to account for surface variability at each test location. Holes were dug with a diameter slightly smaller than the ring and a depth of at least 3 in. for all fine-grained soils and up to 4 in. or more for granular materials to produce a representative sample volume. The sand cone density device and accessories are shown in Figure 6. Figure 6. Sand cone density apparatus and accessories. 2.2.5 Hot plate In this study, the hot plate method was used as a rapid tool for measuring moisture content in the field and to determine the moisture offset for the CASE. The hot plate method consisted of an electric portable stove (Waring model SB30 1300 Watt single burner) that applied direct heat to the soil (Figure 7). An aluminum specimen container (pan) was initially weighed empty, and then it was weighed with the soil sample before and during heating of the sample. The stove was set in a high heat mode, and the sample container was placed on the stove similar to a conventional stovetop. The soil sample was stirred while heating to expedite the drying process. The specimen container was removed from the heat and weighed at frequent intervals (1 to 5 min.) that depended on the initial moisture of the soil. The heating and weighing process was repeated until a change in soil mass of less than one percent occurred during a 1-min interval. At that point, the moisture content was calculated. Data were monitored using the ERDC Rapid Soil Analysis Kit software (Berney and Wahl 2008) converted to an Android app running on a Motorola Xoom tablet to provide real-time computation of moisture content and change detection during the drying process. ERDC/GSL TR-16-28 12 Figure 7. Hot plate, scale, and accessories used to determine soil moisture content. 2.2.6 Laboratory oven Drying of the soil using the laboratory oven test was the reference standard for comparing the effectiveness of the alternative devices in measuring soil moisture content and the hot plate. The oven temperatures and controls were set to 230 ºF ± 9 ºF according to ASTM E149 (ASTM International 1994), and the samples were heated overnight (minimum 15 hr) according to ASTM 2216 (ASTM International 2010b). ERDC/GSL TR-16-28 13 3 Experimental Procedures 3.1 Soil test section 3.1.1 Test strip construction A total of 12 test strips were constructed at ERDC under a large covered hangar to help protect the soils from the elements. Each soil was prepared to the desired moisture (as listed in Table 3) by letting it air-dry or by wetting it using a hydro-seeder depending on the current moisture content of the soil at the time of preparation. A skid steer or front-end loader was used to mix the soil to distribute the moisture more consistently. Some of the soils, especially the CH, required the use of a tiller to loosen the soil, expose more surface area, and allow for more uniform moisture distribution. For test strip construction purposes only, constant monitoring of the soil moisture content was performed by using the standard laboratory microwave oven (ASTM International 2008). Once the soil was at the desired moisture content, it was placed in the test section in two lifts using a dump truck and a skid steer (Figure 8). Table 3. Moisture levels used to prepare each soil for testing. Test Strip Soil ID Moisture Content at time of testing (%) Compaction Level Tested Low High 1 High-Plasticity Clay 26.5 X 2 High-Plasticity Clay 33.7 X 3 Clay-Gravel 8.6 X X 4 Limestone 3.2 X X 5 Limestone 4.9 X X 6 Clay-Gravel 6.2 X X 7 Blended Clayey Sand 7.9 X X 8 Red Clayey Sand 10.5 X X 9 Low-Plasticity Clay 19.7 X X 10 Red Clayey Sand 16.0 X X 11 Blended Clayey Sand 5.0 X X 12 Low-Plasticity Clay 12.7 X X ERDC/GSL TR-16-28 14 Figure 8. Placing soil to build a testbed using a) dump truck and b) skid steer. For each test strip, the first lift placed was approximately two roller widths (10 ft) across to provide a wide enough base to create a top layer at least 8 ft across. The test items were constructed in two 6-in.-thick compacted lifts, such that the final test section was 12 in. thick to provide a suitable thickness of uniform soil above the natural subgrade to ensure that the response of each instrument was not influenced by the subgrade layer’s properties. The test items were considered ready for testing when the second lift was at the specified compaction level. The order in which the soil test strips (1 through 6) were constructed is listed in Table 3. The clay gravel, limestone, blended clayey sand, low-plasticity clay, and red clayey sand were compacted using a Caterpillar CS433E 7-ton vibratory smooth drum roller (Figure 9a). The high-plasticity clay was compacted using an Ingram 35-ton rubber tire compactor (Figure 9b). In order to maintain a smooth surface for testing the gauges, the finer grained soils when compacted on the wet side of optimum required and placement of a plastic sheet over the test section during the compaction process to prevent adherence of the soil to the roller drum (Figure 10). Figure 9. Soil compaction equipment: a) smooth drum roller and b) rubber tire compactor. a) b) a) b) ERDC/GSL TR-16-28 15 Figure 10 . Use of plastic sheet on test strip to prevent soil adhering to the drum. During the compaction of the first 6-in. lift, NDG readings were obtained after each roller pass or after a series of passes to determine the number of roller passes required to achieve low- and high-compaction levels. This varied for each soil and moisture level. A single sand cone test was conducted at the completion of the first lift along with the CASE and eGauge to provide device calibration for the second lift. Full test data were collected on the second lift at the predetermined low- and high- compaction levels. 3.1.2 Test procedures Testing was conducted as compaction progressed. Density and moisture content measurements were obtained with two CASE units, the eGauge, and the NDG at two different compaction levels (low and high). Only the high- plasticity clay was tested at one level of compaction. The CH soil compacts very easily when wet making it difficult to identify different compaction levels with the equipment used. Also, when the CH soil is on the dry side of the compaction curve, it is difficult to compact causing a rough compacted surface, which does not allow accurate density measurements. The number of roller coverages required for completing each compaction level varied with soil type and moisture condition. One coverage of the roller consisted of one pass down the test strip and one pass going back. Figure 11 shows typical test layouts for each test strip. Each test strip was divided into three test areas. At each compaction level, three readings were obtained with each instrument in the three test areas (R1, R2, and R3). A ERDC/GSL TR-16-28 16 typical instrument layout is shown in Figure 12. Soil samples were obtained from each sand cone test location for standard oven moisture content determination and additional soil samples were collected nearby for moisture content determination using the hot plate (Figure 13 and Figure 14.) Since the soil surface was disturbed after sampling at the low compaction effort, the test locations changed for the high compaction level (i.e., low (L) and high (H)) as shown in Figure 11. The cloverleaf pattern identified in the figures was used once per soil type to observe device precision for the CASE unit by measuring moisture and density in the same location 10 times to note any variance for the same test location (Figure 15). Figure 11. Typical test item layout. Figure 12. Typical instrument layout. ERDC/GSL TR-16-28 17 Figure 13. Testing of sand cone density following CASE, NDG, and eGauge measurements and testing of hot plate moisture content inside red ring. Figure 14 . Posttest locations of sand cone and hot plate samples following testing on limestone test section. ERDC/GSL TR-16-28 18 Figure 15. Cloverleaf pattern used for precision evaluation of CASE unit. Sequencing of the test devices began with the CASE unit on the undisturbed surface. This was followed by driving the nuclear gauge compaction rod at each of the three test locations to establish a hole to a depth of at least 8 in. below the compacted surface (Figure 16). The NDG was tested on all three test sites, R1, R2 and R3, at a depth of 6 in., and readings were obtained in two directions around the hole at approximately 90-deg from each other. The NDG was then placed at least 30 ft from the test area before the eGauge was used so as not to influence the low active source in the eGauge device (Figure 17). A wet density was obtained from the eGauge at a rod depth of 6 in., which is a 4-in. depth equivalent for this gauge (Figure 18). Wet densities were obtained in two directions similar to the NDG. Following both the NDG and eGauge density measurements, the moisture probe was then inserted into the hole to obtain the moisture content value that is required to extend at least 8 in. into the soil (Figure 19). The moisture probe was rotated around a 90-deg arc to obtain two moisture readings that coincide with the two eGauge positions. ERDC/GSL TR-16-28 19 Figure 16. Driving of the nuclear gauge compaction rod for NDG and eGauge testing. Figure 17 . NDG testing alongside the CASE unit. ERDC/GSL TR-16-28 20 Figure 18. eGauge wet density measurement with rod at 6-in. depth. Figure 19. Insertion of the moisture probe following density eGauge testing. 3.1.3 Internal gauge calibration The NDG was calibrated each test day prior to use as per ASTM D6938 (ASTM International 2010). This ensured that radiation counts were within the proper limits. The NDG was then used for the remainder of the test day without subsequent calibration. ERDC/GSL TR-16-28 21 The combined asphalt and density evaluator (CASE) did not require any pre-calibration prior to collecting data. Its internal software automatically selects the proper regression algorithm to use by analyzing certain features found within the frequency-response curves. The CASE does require calibrated offsets for both wet density and moisture content derived from the sand cone and hot plate. These were obtained from the sand cone wet density and hot plate moisture content on the first completed lift on each test strip and entered into the CASE prior to obtaining data on the completed second lift. This represented a typical field scenario where time to complete an oven moisture content would not be possible to allow operations to continue. The eGauge requires a standard count be performed on each unique soil to be tested. Therefore, a standard background count was obtained on the completed first lift of each test strip. No moisture calibrations were applied to the readings returned from the eGauge’s moisture probe at the time of testing. 3.2 Asphalt test section 3.2.1 Test procedures To evaluate the ability of the CASE and eGauge to measure asphalt density accurately, measurements were obtained on a series of three different existing dense graded asphalt sections from prior research projects at the ERDC Waterways Experiment Station (WES) campus. Three different sections were selected of varying depth and surface texture. Figure 20 was a well-weathered shoulder section of approximately 4-in. depth with a rough surface texture (RT). Figure 21 shows a well prepared surface section with a smooth surface texture (ST) and a depth of approximately 4-in. Figure 22 shows a thick asphalt layer (DP) approximately 8-in. thick to evaluate accuracy of the devices with thicker pavement layering. Each asphalt section was marked at three locations where device testing would occur as shown in Figure 22. A generator powered combihammer with a ¾-in.-diameter bit was used to drill a hole for insertion of the NDG and eGauge density rods (Figure 23). The CASE unit was tested adjacent to the hole in a manner similar to Figure 20. ERDC/GSL TR-16-28 22 Figure 20. eGauge placed on rough-textured (RT) asphalt section. Figure 21 . Smooth textured (ST) asphalt section (note the transition to RT at top of photo). ERDC/GSL TR-16-28 23 Figure 22. Deep (DP) asphalt test section with pencil shown for thickness scale. Figure 23. Use of a combihammer to drill holes in asphalt for density probe insertion. 3.2.2 Gauge validation For this project, core samples for bulk specific gravity determination were obtained at the same test locations as the CASE devices and adjacent to the eGauge and NDG holes following testing of each device. Densities of the asphalt core specimens were obtained according to AASHTO T166 (AASHTO 2011). Four-inch-diam core samples were extracted from the asphalt to the full depth of the layer at each test location (4 in. for ST and RT sections and 6 in. for DP section). Bulk densities were determined from the asphalt cores using the Corelok (ASTM International 2012a) and SSD (ASTM International 2012b) methods in increments of 2 in., 4 in., and 6 in. for the DP samples. For 6-in.-tall cores, the density of the entire sample was obtained, then the bottom 2 in. were sawed off and the 4-in.- ERDC/GSL TR-16-28 24 tall core was tested, and finally the last 2 in. were sawed off leaving only a 2-in.-tall core to complete evaluation of the density (Figure 24). A similar approach was taken with the 4-in.-thick core samples where only the 2-in.- and 4-in.-thick densities were obtained. These density values were compared to the backscatter/surface readings of the gauges along with their readings recorded at every 2-in. depth into the pavement. Raw data are listed in Appendix B. Figure 24 . Illustration of core separation to obtain densities at each 2-in. thickness. 2” 4” 6” Saw lines ERDC/GSL TR-16-28 25 4 Data Analysis and Results 4.1 Soil test section 4.1.1 Range of soil conditions evaluated To provide a means of assessing gauge performance over a range of moisture contents and densities typical of a field construction, each of the six soil types was tested at a high and low moisture along with a high and low density. Attention was paid to ensure that moisture values were near the OMC for all soils except for the Buckshot clay that has inherent constructability problems at dry moisture contents. For all other soils, the relative density ranged from average values of 82 percent to 96 percent of modified MDD for the high-low comparison and an average moisture content range of 1.8 percent below OMC to 3.4 percent above OMC (Table 4). These ranges are considered typical of most horizontal construction activities, and therefore provide a good evaluation of how the devices will capture the necessary data for quality control. Figure 25 illustrates the data points collected during the full scale test section construction with respect to the modified proctor density curve. Table 4. Range of relative density and moisture content achieved during construction. MDD OMC Max Min Low High Buckshot 104.3 22.4 94%82%-4.3 13.76 Clay Gravel 133.1 7.4 97%89%0.7 3.44 Limestone 145.7 4.7 99%82%1.61 0.33 Low plasticity clay 118.1 13.7 98%73%1.3 6.7 Blended sandy clay 134.8 7.4 97%87%2.7 0.8 Red clayey sand 119.8 12.5 94%83%2.5 5.5 Averages:96%82%1.8 3.4 CH SC w/gravel GW-GC CL Blended-SC Red-SC Dry density range Moisture range ERDC/GSL TR-16-28 26 Figure 25. Moisture-density range tested for each soil type. 4.1.2 Hot plate moisture correlation to laboratory oven dried procedure A previous study by Berney et al. (2013) identified a number of alternatives to measure field moisture content without the use of a conventional oven or NDG. The open flame burner was determined to be the most accurate technique of all those tested being superior even to the NDG. At the time of the study, the hot plate method was not tested, but independent studies at ERDC suggest it could be used as a reliable 80 85 90 95 100 105 110 18 23 28 33 38 Dr y D e n s i t y ( p c f ) Moisture Content (%) Modified Proctor Field Data M1 Field Data M2 Buckshot clay 116 118 120 122 124 126 128 130 132 134 3 5 7 9 11 13 Dr y D e n s i t y ( p c f ) Moisture Content (%) Modified Proctor Field Data M1 Field Data M2 Clay Gravel 115 120 125 130 135 140 145 150 0 2 4 6 8 Dr y D e n s i t y ( p c f ) Moisture Content (%) Modified Proctor Field Data M1 Field Data M2 Limestone 90 95 100 105 110 115 120 8 10 12 14 16 18 20 22 Dr y D e n s i t y ( p c f ) Moisture Content (%) Modified Proctor Field Data M1 Field Data M2 Low plasticity clay 116 118 120 122 124 126 128 130 132 134 136 3 5 7 9 11 Dr y D e n s i t y ( p c f ) Moisture Content (%) Modified Proctor Field Data M1 Field Data M2 Blended clayey sand 95 100 105 110 115 120 125 8 10 12 14 16 18 20 Dr y D e n s i t y ( p c f ) Moisture Content (%) Modified Proctor Field Data M1 Field Data M2 Red clayey sand ERDC/GSL TR-16-28 27 alternative, since it is similar in function to the open flame burner. For each test location used for determining density, a separate soil sample was obtained and split between the oven and a hot plate to provide a one-to- one comparison of moisture content. The hot plate soil sample was dried until less than a 1 percent change in overall soil mass occurred, and the oven dried soil was dried according to ASTM International (2008) as outlined in Chapter 2. A comparison of moisture contents across all soil samples tested is shown in Figure 26 with a resultant coefficient of determination of 99 percent. This indicates that for soils of both high and low moisture contents, proper use of the hot plate can yield moisture content values with accuracy exceeding that of the NDG. These results compare favorably with the accuracy of the open flame burner. Therefore, the hot plate system can be used as a rapid field technique to validate and calibrate moisture readings obtained from either the CASE or the eGauge to ensure that proper data are obtained from each device. Figure 26. Comparison of hot plate versus oven dried moisture content techniques. 4.1.3 CASE calibration It was noted in the literature review that, for the CASE gauge to return moisture content and wet/dry density data in the proper range, it must be calibrated with some secondary moisture and density device. In this study, the sand cone and the hot plate were used for this purpose. To determine the effectiveness of this approach, Figure 27 and Figure 28 illustrate that a 0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30 35 40 Ho t P l a t e M o i s t u r e C o n t e n t ( % ) Oven Moisture Content (%) Buckshot Clay (CH) Clay Gravel (SC)Limestone (GW-GC) Low Plasticity Clay (CL)Blended Clayey Sand (SC)Red Clayey Sand (SC) R2 = 0.986 ERDC/GSL TR-16-28 28 one-to-one comparison of sand cone to the NDG for wet density and dry density returned R2 values of 87 percent and 95 percent, respectively. This suggests that using the sand cone wet density and hot plate moisture content to calibrate the CASE should enable this device to return the correct values. Figure 27 . Comparison of wet density between sand cone and NDG. Figure 28. Comparison of dry density between sand cone and NDG. To calibrate the CASE unit for this study, the device was placed on the soil of interest in a prepared condition similar to expected during construction, in this case following the final roller pass on the first lift. A wet density and 110 115 120 125 130 135 140 145 150 155 160 110 120 130 140 150 160 Sa n d C o n e W e t D e n s i t y ( p c f ) NDG Wet Density (pcf) Buckshot Clay (CH) Clay Gravel (SC)Limestone (GW-GC) Low Plasticity Clay (CL)Blended Clayey Sand (SC)Red Clayey Sand (SC) R2 =0.87 80 90 100 110 120 130 140 150 80 90 100 110 120 130 140 150 Sa n d C o n e D r y D e n s i t y ( p c f ) NDG Dry Density (pcf) Buckshot Clay (CH) Clay Gravel (SC)Limestone (GW -GC) Low Plasticity Clay (CL)Blended Clayey Sand (SC)Red Clayey Sand (SC) R2 =0.95 ERDC/GSL TR-16-28 29 moisture content reading were then obtained. A sand cone test was conducted directly below where the CASE gauge was tested, and a sample of soil was obtained from the sand cone spoils to conduct a hot plate moisture content and an oven dried moisture content for validation. Figure 29 and Figure 30 show the wet density and moisture content differentials occurring between the raw CASE readings for the two replicate gauges CASE 1 and CASE 3 and the calibration method. There exist two distinct trends of the differential; as both wet density and moisture content of the true soil density increase, the magnitude of the offset increases as well. The density and moisture content have opposing parabolic trends in their responses such that when combined in Figure 31, the dry density is represented by a linear offset with a high R2 of 97 percent. While this calibration seems to provide the proper correction to the CASE readings, it is somewhat disconcerting that the initial readings of the CASE are so far from the true value. This suggests that the internal calibration mechanisms in the gauge lack the ability to properly interpret soil type to correct initial readings. Figure 29. Wet density differential for CASE gauge during calibration. y = -0.0238x2 + 8.5665x -686.92 R² = 0.8374 y = -0.0167x2 + 6.3793x -515.38 R² = 0.8733 -30 -20 -10 0 10 20 30 40 50 60 70 80 100 110 120 130 140 150 160 De n s i t y d i f f e r e n t i a l f r o m C A S E g a u g e t o S a n d Co n e ( p c f ) Wet Density from Sand Cone (pcf) CASE 1 CASE 3 Poly. (CASE 1) Poly. (CASE 3) ERDC/GSL TR-16-28 30 Figure 30. Moisture content differential for the CASE gauge during calibration. Figure 31 . Dry density differential for the CASE gauge during calibration. 4.1.4 eGauge calibration The eGauge does not require a standard count calibration like the higher radioactive sources in the NDG. However, because the eGauge is so sensitive to background radiation, a standard background radiation count at the test location or soil of interest should be performed prior to collecting wet density data. For this study, the eGauge was placed on the soil of interest prior to testing on the first compacted lift, and a standard background radiation count was obtained on the device. The wet density y = 0.0182x2 + 0.0076x -1.5408 R² = 0.9308 y = 0.0191x2 -0.0595x -0.9965 R² = 0.9105 -10 -5 0 5 10 15 20 25 0 10 20 30 40 Mo i s t u r e d i f f e r e n t i a l f r o m C A S E g a u g e t o H o t Pl a t e ( % ) Moisture content from Hot Plate (%) CASE 1 CASE 3 Poly. (CASE 1) Poly. (CASE 3) y = 1.6571x -173.66 R² = 0.9555 y = 1.456x -142.86 R² = 0.9704 -60 -40 -20 0 20 40 60 80 80 100 120 140 160 Dr y D e n s i t y d i f f e r e n t i a l f r o m C A S E g a u g e t o Sa n d C o n e ( p c f ) Dry Density from Sand Cone (pcf) CASE 1 CASE 3 Linear (CASE 1) Linear (CASE 3) ERDC/GSL TR-16-28 31 was performed first, followed by the moisture content reading with the electronic probe. The probe was rotated in the hole, and the highest observed moisture read was noted in the data sheets as this tended to be the closest approximation to the actual moisture content and suggested good sensor contact with the soil face. The sand cone moisture sample could be used as a calibration tool for the moisture reading on the eGauge. For this study, an observation was made between the moisture content and the eGauge to determine if an offset was necessary and, in most instances, the tested moisture content differential was ± 1.5 percent on average and not considered substantial enough to include as an actual correction. This is similar to the offsets normally encountered in the NDG that are usually ignored during construction operations. When applied, the moisture calibration is similar to the CASE in that the moisture content is computed from the oven or hot plate and a linear offset is applied to the moisture content returned from the eGauge. No calibration offsets were applied to the wet density, similar to the NDG approach, and the resultant wet density was used directly in all comparisons. 4.1.5 CASE and eGauge correlations to NDG Following data collection, the calibration offsets were applied to the CASE readings, and the eGauge was used without any offsets. Data were obtained from two different CASE gauges. To simplify the analysis, the average of the readings obtained from gauges CASE 1 and CASE 3 were used for comparison to the NDG. Figure 32 and Figure 33 illustrate the overall correlations of wet and dry density for the eGauge and the CASE devices versus the NDG. The eGauge exhibited a high correlation with R2 = 94 percent for both wet and dry density, whereas the CASE exhibited a lower correlation with 59 percent and 84 percent for wet and dry density, respectively. ERDC/GSL TR-16-28 32 Figure 32. Correlation of eGauge density to NDG. Figure 33. Correlation of CASE density to NDG. Figure 34 and Figure 35 show the correlation of the device moisture content readings to the NDG and the oven dried moisture technique. The CASE exhibits a high correlation to the oven dried moisture content which helps offset the poor wet density correlation producing a suitable dry density. The eGauge moisture content has a lower correlation near 86 percent with much of this error being attributable to the fluctuation of moisture readings while maneuvering the electronic probe in the ground. y = 1.0838x -10.536 R² = 0.9367 y = 1.1595x -17.869 R² = 0.9456 90 100 110 120 130 140 150 160 90 100 110 120 130 140 150 160 eG a u g e w e t / d r y d e n s i t y ( p c f ) Nuclear Density Gauge wet/dry density (pcf) eGauge-Wet eGauge-Dry Linear (eGauge-Wet) Linear (eGauge-Dry) y = 0.9151x + 14.222 R² = 0.5933 y = 1.124x -11.225 R² = 0.8349 90 100 110 120 130 140 150 160 90 100 110 120 130 140 150 160 CA S E w e t / d r y d e n s i t y ( p c f ) Nuclear density gauge wet/dry density (pcf) CASE-Wet CASE-Dry Linear (CASE-Wet) Linear (CASE-Dry) ERDC/GSL TR-16-28 33 Figure 34. Correlation of eGauge moisture content to NDG/Oven. Figure 35. Correlation of CASE moisture content to NDG/Oven. The prior correlations represent the device response when considering all the varying soil classifications combined. Such high correlation values, when all soils data are considered, indicates the CASE and eGauge are able to accurately distinguish moisture-density response between soil types; for example a clay displays a much lower dry density than a limestone and the reverse is true for moisture content. However, of more importance is the ability of each gauge to measure small changes in density within a single y = 1.206x -2.3824 R² = 0.8875 y = 1.0955x -1.1502 R² = 0.8573 0 5 10 15 20 25 30 35 40 45 0 10 20 30 40 e G a u g e m o i s t u r e c o n t e n t ( % ) NDG or Oven dried moisture content (%) eGauge-NDG eGauge-Oven Linear (eGauge-NDG) Linear (eGauge-Oven) y = 1.1854x -1.8778 R² = 0.9818 y = 1.0956x -0.886 R² = 0.9818 0 5 10 15 20 25 30 35 40 45 0 10 20 30 40 CA S E m o i s t u r e c o n t e n t ( % ) NDG or Oven dried moisture content (%) CASE-NDG CASE-Oven Linear (CASE-NDG) Linear (CASE-Oven) ERDC/GSL TR-16-28 34 soil as compactor passes or moisture changes from one test section to the next. Figure 36 illustrates the correlations between high and low compaction levels for all soils combined. These plots show a loss of fidelity between the eGauge and the CASE compared to the NDG when testing on the same soil at a few versus many roller passes. Figure 36. Comparison of density between eGauge and CASE to the NDG at both high (HI) and low (LO) compaction efforts. The eGauge continues to show a high level of accuracy for both wet and dry density, with a change in correlation from 95 percednt at high compaction to about 92 percent at low compaction. This suggests the eGauge can detect subtle changes in density during compaction operations, a key measure in quality control. The CASE gauge has a larger change in correlation of dry density going from a 92 percent correlation at high compaction but dropping to 80 percent at low compaction efforts. Wet density has an even poorer correlation for the CASE, which does not have the moisture calibration to improve its accuracy. y = 1.0366x -3.9603 R² = 0.9474 y = 1.1399x -15.353 R² = 0.9495 90 100 110 120 130 140 150 160 90 100 110 120 130 140 150 160 eG a u g e w e t / d r y d e n s i t y ( p c f ) Nuclear Density Gauge wet/dry density (pcf) eGauge-Wet-Hi eGauge-Dry-Hi Linear (eGauge-Wet -Hi) Linear (eGauge-Dry-Hi) y = 1.1137x -14.797 R² = 0.9151 y = 1.2024x -23.065 R² = 0.9392 90 100 110 120 130 140 150 90 100 110 120 130 140 150 160 eG a u g e w e t / d r y d e n s i t y ( p c f ) Nuclear Density Gauge wet/dry density (pcf) eGauge-Wet-Lo eGauge-Dry-Lo Linear (eGauge-Wet -Lo) Linear (eGauge-Dry-Lo) y = 1.0556x -7.0118 R² = 0.768 y = 1.1276x -14.71 R² = 0.9164 90 100 110 120 130 140 150 160 90 100 110 120 130 140 150 160 CA S E w e t / d r y d e n s i t y ( p c f ) Nuclear density gauge wet/dry density (pcf) CASE-Wet-Hi CASE-Dry-Hi Linear (CASE-Wet-Hi) Linear (CASE-Dry-Hi) y = 0.9937x + 7.8751 R² = 0.6049 y = 1.1661x -12.386 R² = 0.8009 90 100 110 120 130 140 150 160 90 100 110 120 130 140 150 160 CA S E w e t / d r y d e n s i t y ( p c f ) Nuclear density gauge wet/dry density (pcf) CASE-Wet-Lo CASE-Dry-Lo Linear (CASE-Wet-Lo) Linear (CASE-Dry-Lo) ERDC/GSL TR-16-28 35 To assess the measurement capability of each gauge within a unique soil type, comparisons of wet and dry density of the eGauge and CASE to the NDG for each individual soil type tested are shown in Figure 37 and Figure 38. The correlations include both moisture content levels tested (for all soils but CH) and the High-Low density values at varying pass levels. Figure 37 . Comparison of dry density between CASE and eGauge versus NDG by soil type. y = 1.0143x -0.1778 R² = 0.931 y = 0.2716x + 104.43 R² = 0.4397 120 125 130 135 140 145 150 115 125 135 145 De v i c e d r y D e n s i t y ( p c f ) Nuclear Density Gauge dry density (pcf) eGauge-GW-GC CASE-GW-GC Linear (eGauge-GW-GC) Linear (CASE-GW-GC) y = 1.2599x -28.7 R² = 0.6114 y = 0.3796x + 81.761 R² = 0.0385 116 118 120 122 124 126 128 130 132 134 136 138 116 118 120 122 124 126 128 130 De v i c e d r y d e n s i t y ( p c f ) Nuclear Density Gauge dry density (pcf) eGauge-SC-Gravel CASE-SC-Gravel Linear (eGauge-SC- Gravel) Linear (CASE-SC- Gravel) y = -0.2538x + 112.27 R² = 0.1453 y = 0.5929x + 32.791 R² = 0.321 80 82 84 86 88 90 92 94 86 88 90 92 94 96 98 100 De v i c e d r y d e n s i t y ( p c f ) Nuclear Density Gauge dry density (pcf) eGauge-CH CASE-CH Linear (eGauge-CH) Linear (CASE-CH) y = 1.0312x -6.194 R² = 0.6037 y = 0.6043x + 47.094 R² = 0.3515 90 95 100 105 110 115 120 90 100 110 120 De v i c e d r y d e n s i t y ( p c f ) Nuclear Density Gauge dry density (pcf) eGauge-Red-SC CASE-Red-SC Linear (eGauge-Red -SC) Linear (CASE-Red-SC) y = 1.373x -43.304 R² = 0.8569 y = 0.5221x + 58.261 R² = 0.3158 110 115 120 125 130 135 140 110 120 130 140 De v i c e d r y d e n s i t y ( p c f ) Nuclear Density Gauge dry density (pcf) eGauge-Blended-SC CASE-Blended-SC Linear (eGauge-Blended-SC) Linear (CASE-Blended-SC) y = 0.8387x + 16.733 R² = 0.7659 y = 0.6174x + 40.281 R² = 0.5585 94 96 98 100 102 104 106 108 110 112 114 90 100 110 120 De v i c e d r y d e n s i t y ( p c f ) Nuclear Density Gauge dry density (pcf) eGauge-CL CASE-CL Linear (eGauge-CL) Linear (CASE-CL) ERDC/GSL TR-16-28 36 Figure 38. Comparison of wet density between CASE and eGauge versus NDG by soil type. Figure 39 summarizes the coefficients of determination for each gauge and each soil type in both the wet and dry density comparisons. The eGauge was far superior to the CASE unit for all soils tested showing the best correlation in the wet density configuration. The average correlation of the eGauge versus the CASE unit was 75 percent versus 35 percent for dry densities and 88 percent versus 38 percent for wet densities, suggesting y = 0.9873x + 2.6205 R² = 0.9563 y = 0.5096x + 76.592 R² = 0.5894 120 125 130 135 140 145 150 155 160 120 130 140 150 160 De v i c e w e t D e n s i t y ( p c f ) Nuclear Density Gauge wet density (pcf) eGauge-GW-GC CASE-GW-GC Linear (eGauge-GW-GC) Linear (CASE-GW-GC) y = 1.1542x -20.42 R² = 0.6934 y = -0.1148x + 153.9 R² = 0.0087 120 125 130 135 140 145 150 126 128 130 132 134 136 138 140 De v i c e w e t d e n s i t y ( p c f ) Nuclear Density Gauge wet density (pcf) eGauge-SC-Gravel CASE-SC-Gravel Linear (eGauge-SC-Gravel) Linear (CASE-SC-Gravel) y = 0.7292x + 32.579 R² = 0.4112 y = 0.0667x + 108.43 R² = 0.0014 110 112 114 116 118 120 122 124 126 128 114 116 118 120 122 124 126 De v i c e d r y d e n s i t y ( p c f ) Nuclear Density Gauge dry density (pcf) eGauge-CH CASE-CH Linear (eGauge-CH) Linear (CASE-CH) y = 1.2623x -33.907 R² = 0.8574 y = 0.4355x + 73.681 R² = 0.3095 105 110 115 120 125 130 135 110 120 130 De v i c e w e t d e n s i t y ( p c f ) Nuclear Density Gauge wet density (pcf) eGauge-Red-SC CASE-Red-SC Linear (eGauge-Red - SC) y = 1.0523x -5.9153 R² = 0.9698 y = 0.7397x + 32.491 R² = 0.5552 110 115 120 125 130 135 140 145 120 130 140 150 De v i c e w e t d e n s i t y ( p c f ) Nuclear Density Gauge wet density (pcf) eGauge-Blended-SC CASE-Blended-SC Linear (eGauge-Blended -SC) Linear (CASE-Blended -SC) y = 1.2577x -30.431 R² = 0.9085 y = 0.267x + 90.908 R² = 0.4241 110 115 120 125 130 135 110 120 130 140 De v i c e w e t d e n s i t y ( p c f ) Nuclear Density Gauge wet density (pcf) eGauge-CL CASE-CL Linear (eGauge-CL) Linear (CASE-CL) ERDC/GSL TR-16-28 37 the eGauge has the ability to capture small changes in density during compaction operations for a unique soil, whereas the CASE is incapable of providing this type of information. The CASE readings tended to be too random to provide subtle density differences that are critical to establishing end of compaction operations during quality control. Neither gauge was effective at capturing density changes for the heavy Buckshot clay material (CH). Figure 39. Density correlation by soil type between eGauge and CASE to the NDG. This behavior is further emphasized in Figure 40, which shows the average change in dry density between the low and high density test items for each soil type and moisture content. All the bars should move in the same direction and be of similar height, as there should be a large change in density and always increasing with passes. However, the CASE data often has little differential or the bars move in the opposite direction to the other density techniques. For most of the test items, the CASE unit recorded a higher density at the low compaction effort and a lower density at the higher compaction effort. This is counter to the actual field response noted in the NDG and sand cone devices. This is a dangerous precedent set by the CASE, as it suggests little confidence can be placed in the density readings it provides during field construction. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% CH Gravel SC GW-GC CL Blended SC Red SC AVG AVG w/o CH Co e f f i c i e n t o f D e t e r m i n a t i o n ( % ) eGauge CASE ERDC/GSL TR-16-28 38 Figure 40. Density differential between compaction efforts by soil type for each density test procedure. 4.1.6 Summary of performance 4.1.6.1 Error in moisture sensor for eGauge The eGauge provides an excellent reproduction of the wet density because of a similarity to the NDG in the radioactive source technology that is used. However, the introduction of a secondary electronic probe for moisture content measurements is a less accurate technology than the neutron emissions from the NDG. In practice, the eGauge can yield an even greater error than that reflected in the correlation plots owing to the technique used to insert the gauge. To properly conduct the moisture experiment, the manufacturer recommends insertion of the moisture probe into the pre-drilled rod hole prior to insertion of the density rod or in a secondary hole adjacent to the density hole. This has the advantage of allowing the moisture probe to have better sidewall contact with the hole which is critical to obtaining the best possible moisture reading. However, extraction of the moisture probe can cause collapse of the sidewalls and prevent obtaining a density reading, as noted by the researchers in preliminary studies on the moisture probe. Friable soils like silts or a dry limestone, as well as many coarse grained soils, tend to have trouble -15 -13 -11 -9 -7 -5 -3 -1 1 3 5 GC-1 GC-2 GW-1 GW-2 CL-1 CL-2 SM-1 SM-2 SC-1 SC-2 De n s i t y d i f f e r e n t i a l b e t w e e n c o m p a c t i o n e f f o r t s ( c o n s t a n t mo i s t u r e c o n t e n t ) ( p c f ) NDG eGauge SC CASE 1 CASE 3 ERDC/GSL TR-16-28 39 maintaining an open probe hole when disturbed by the moisture probe. To mitigate this effect during the study, the moisture probe was inserted after insertion of the density rod to ensure that moisture and density readings occurred at the same location along with the NDG rod. The moisture probe still maintained good sidewall contact as the density rods did little to disturb the hole, but it was noted that often the initial moisture reading was low compared to the expected value. The operator would then rotate and jostle the moisture probe, continually observing the moisture measurements on the digital display as the probe had better or worse sidewall contact, and noted the highest reading displayed. The correlations shown in Figure 34 were based on the highest reading obtained by the moisture probe in this rotating pattern. This subjectivity to obtaining the moisture reading may put the point-wise accuracy of this feature of the eGauge into question. It is recommended that a hot plate or alternative moisture content be taken on the soil of interest to ensure that the eGauge is obtaining readings in the proper range. 4.1.6.2 Error in the CASE unit As noted in Berney et al. (2013, 2014), the CASE gauge requires calibration with a secondary moisture and density device prior to its use as the internal algorithms do not provide a valid moisture or density reading. This process was implemented in this study and Figure 29 and Figure 30 show the extent to which the initial CASE readings varied from the sand cone density and hot plate moisture contents before a linear offset was applied. The CASE exhibited an ability to accurately capture the moisture content across almost all soil types when properly calibrated. The use of electrical impedance in the CASE’s frequency band is optimal for this type of reading. However, this same frequency band has difficulty picking up subtle changes in soil density, which is evidenced in Table 5. The CASE unit is not a functional tool for determining changes in density during the compaction process. Readings on the CASE can be misleading to the user as to whether a threshold density has been reached. Because of calibration issues, the CASE cannot be used as a forensic tool but rather only in a continuous duration horizontal construction, which is a similar conclusion to that drawn in Berney et al. (2014). ERDC/GSL TR-16-28 40 4.2 Asphalt test section 4.2.1 Summary of performance Table 5 is a summary of the average bulk density values collected from the ERDC asphalt test sites. A zero-inch depth of measurement refers to a backscatter reading obtained with the NDG or a non-destructive surface reading from the CASE unit. All of the reading depths below 0 in. occurred from the insertion of the density rod into a cored hole in the asphalt for the NDG and eGauge devices. The CASE Corr is the corrected value of density from calibration of the CASE unit to the first core sample taken from each test location similar to the approach recommended in Berney et al. (2014). To provide a comparison between the CASE data and the core samples, the core density for a 2-in.-tall sample was used as this represents the data closest to the surface. All other core densities represent the density of the asphalt over the thickness noted. Table 5. Average asphalt density readings for the tested devices. For the NDG, the average density differential between the core samples and the NDG readings is approximately 5 pcf in the current study (Table 5). 4.2.2 CASE and eGauge correlations to NDG and core samples It was noted in Berney et al. (2014) that the calibrated CASE unit performed better than the NDG for warm and hot mix asphalt mixtures placed during construction. The CASE unit exhibited the lowest standard deviation from the core density for these material types. In the current study, the data were scattered when looking at the average density Depth to easureme Core NDG eGauge CASE CASE Corr 0"140.2 139.2 143.1 2"143.3 139.9 140.8 4"145.1 141.6 144.4 0"145.7 146.2 145.7 2"143.3 141.2 141.0 4"145.1 143.1 142.1 0"123.2 133.8 143.1 2"141.8 136.5 138.8 4"141.3 135.8 136.9 6"141.3 135.8 136.9 Sample Type RT-Rough Texture ST-Smooth Texture DP-Deep Sample Average Density (pcf) ERDC/GSL TR-16-28 41 deviation from the core value of each asphalt type, as there were not enough samples taken for a standard deviation comparison (Figure 41). When calibrated, the CASE unit achieves the best results only for the DP asphalt layer whereas the eGauge proved to be the most consistent device across all asphalt types. The CASE gauge’s accuracy to the core samples is improved when calibrated, but it results in a poorer correlation to the NDG unit. The eGauge provides an improvement over the NDG in density differential with the cores. Given the consistent offset magnitude of the NDG across asphalt depths and types noted earlier, the eGauge should similarly provide a more accurate estimate of the true core density. Figure 41 . Average deviation of asphalt bulk density between NDG, CASE, and eGauge versus core samples. Table 6 displays the summary correlation of determination across all the devices tested along with all the asphalt cores. What is evidenced in this chart is that the eGauge has the highest correlation with the core samples (87 percent), and the NDG has a high correlation with the CASE (87 percent). This is notable in that the CASE was designed to approximate the backscatter readings of the NDG. The raw eGauge and the NDG data do not agree well (49 percent) when comparing density with the probe inserted into the asphalt. However, when comparing the averages across each asphalt type, the eGauge compares similarly to the NDG (Figure 42). It is unclear why the poor correlation when comparing the test items side by side. 0 1 2 3 4 5 6 7 8 9 10 RT ST DP Av e r a g e d e v i a t i o n f r o m C o r e Sa m p l e ( p c f ) Asphalt Type NDG eGauge CASE CASE Cor ERDC/GSL TR-16-28 42 Table 6. Coefficient of determination between each test device and the core samples. For many years, the NDG has been used as the reference standard in the field lending confidence to the eGauge device for down-hole measurements and the CASE device for the surface readings. The advantage of the eGauge is that it can acquire its density without field calibration unlike the CASE unit. The disadvantage is that a hole must be drilled into the asphalt to obtain the reading unlike the non-destructive NDG and CASE units. The eGauge is not the most ideal device to use for obtaining production asphalt densities during construction; this would favor the CASE device although it correlates poorly with core density. When performing site investigations or forensics of existing asphalt structures, the eGauge becomes well-suited, as it does not require an asphalt core for calibration, which is logistically impractical. Figure 42. Comparison of AVERAGE asphalt bulk density versus NDG and eGauge for all depths tested. Cores NDG eGauge CASE CASE Corr Cores --0.61 0.87 0.18 0.12 NDG --0.49 0.87 0.37 eGauge --0.63 0.26 Coefficient of Determination between Device Types y = 1.9285x -137.01 R² = 0.8595 y = 1.7109x -104.8 R² = 0.8735 134 136 138 140 142 144 146 141 142 143 144 145 146 B u l k d e n s i t y o f d e v i c e r e a d i n g ( p c f ) Bulk density of asphalt core (pcf) NDG eGauge ERDC/GSL TR-16-28 43 5 Conclusions and Recommendations 5.1 Conclusions The goal of this research effort was to identify a non-nuclear testing device that could perform the same functions as a nuclear density gauge (NDG), measuring field moisture content and density, with similar accuracy. This report summarized an effort to validate the performance of two non- nuclear device platforms, the TransTech Combined Asphalt Soil Evaluator (CASE) and the Troxler eGauge for determining field moisture content and density. The CASE unit was the leading electronic alternative gauge, and the eGauge was the leading hybrid electronic-low source nuclear device with measuring characteristics mirroring its nuclear density counterpart. One-to-one comparisons were made between the NDG, the eGauge, and the CASE units on six different soil types of varying densities and moisture contents along with three varying asphalt sections. Figure 43 provides a summary of the data findings derived from this validation study. Figure 43. Summary data from validation study for each device. 0 10 20 30 40 50 60 70 80 90 100 All Soils Tested Individual Soil Type NDG Oven NDG Core Co e f f i c i e n t o f D e t e r m i n a t i o n ( % ) eGauge CASE Asphalt DensityMoisture ContentWet Density ERDC/GSL TR-16-28 44 5.1.1 Soil density • The eGauge was found to capture the wet and dry density far more reliably than the CASE and was able to do so without requiring any calibration to a secondary moisture/density test device as was the case for the CASE. • The eGauge was far superior to the CASE in determining the density of individual soil types during the compaction process. This is a significant finding as the CASE is unable to provide the operator knowledge of when compaction operations have reached their desired state whereas the eGauge does have this ability. 5.1.2 Moisture content • The calibrated CASE unit (calibrated to soil dried on an electric burner) was able to capture the moisture content more accurately than the eGauge. However, the use of the eGauge without calibration is considered an advantage even with a slightly lower accuracy. • In many instances, moisture content in the field is obtained through a secondary process, many of which are simple in operation, and so accuracy of this measurement is not as critical as the density. 5.1.3 Asphalt density • The eGauge matched closest to the density of the core samples and exhibited less variance than the NDG whereas the CASE was the closest match to the NDG readings. • The requirement to have a drilling device on hand to drill a hole in the asphalt limits the suitability of the eGauge to performing this type of measurement. • The integrated TransTech Pavement Quality Indicator asphalt density technology incorporated into the CASE device has a proven track record of success in prior studies and should be considered as an advantage over the eGauge. 5.2 Recommendations Based on the results from this investigation, the following recommendations are made. ERDC/GSL TR-16-28 45 5.2.1 Soil density and moisture content • The eGauge is the superior device for measuring wet and dry density of soil during construction operations comparing most favorably to the NDG. • The requirement to have a calibration technology on hand to operate the CASE unit in soils for both density and moisture content is considered detrimental to its use, and the CASE should not be considered a viable soil device for military operations • While moisture measurements are more accurate using a calibrated CASE device, the advantage goes to the eGauge which, without calibration, provides a reasonable estimate of the soil moisture. Calibration of the eGauge to a secondary moisture device can only improve its accuracy. 5.2.2 Asphalt density • The CASE is the recommended tool for obtaining asphalt density for construction operations when non-destructive methods are preferred or required (calibration of the device to an asphalt core may still be required). • The eGauge is recommended for scenarios when drilling is available and density without device calibration is required. These scenarios might involve contingency evaluations or spot testing on unknown pavement layers. 5.3 Areas for future study The process to identify a replacement to the NDG was initiated 5 years ago, and rapid changes in technology have made selecting a commercial device a moving target. A down-selection of modern devices was made in 2010, with the TransTech Soil Density Gauge being selected as the best candidate. However, the CASE device was developed by TransTech prior to the next validation study and was included in a side-by-side analysis with the SDG. The performance of the SDG and CASE devices was found lacking, and a final attempt to understand these device limitations was initiated for the current study. The eGauge was released just one week before the current study began and appeared to be the type of technology the military has been seeking. ERDC/GSL TR-16-28 46 Based on the results of this study, the eGauge is currently the best technology to provide a high quality soil moisture-density reading as a replacement to the NDG. However, the eGauge lacks extensive field use in the private and military environments, and its long-term performance could certainly reveal limitations that are not obviated in this study. Once this device has seen placement in a variety of working environments, ERDC should reevaluate its potential use and focus in on solving the limitations identified by its user base to refine any published military guidance. The military will continue to seek better devices to replace the NDG that are simple, easy to use, easy to calibrate, light, portable, and minimize operational logistics. However, given density remains a difficult property to obtain through alternative means, the possibility exists that the military will redefine how soil performance is assessed based on moisture and modulus response similar to the path the highway industry is moving. This will require updating military criteria to follow the guidelines presented in the Transportation Research Boards’s Guide for Mechanistic-Empirical Design for Pavements (MEPDG) (TRB 2011). While a complex challenge to implement, the ability to base soil performance on mechanistic properties may provide a better overall means to design and predict performance. ERDC/GSL TR-16-28 47 References American Association of State and Highway Transportation Officials (AASHTO). 2008. Standard method of test for density of in-place hot mix asphalt (HMA) pavement by electronic surface contact devices. Designation TP 68-04. Washington, DC: American Association of State and Highway Transportation Officials. _____. 2011. Standard test method for bulk specific gravity of compacted asphalt mixtures using saturated surface-dry specimens. Designation T 166.Washington, DC: American Association of State and Highway Transportation Officials. ASTM International. 1994. Lab w/c oven temps. Designation E 149-94. West Conshohocken, PA: ASTM International. _____. 2006. Standard test method for sieve analysis of fine and coarse aggregates. Designation C 136. West Conshohocken, PA: ASTM International. _____. 2007a. Determination of water (moisture) content of soil by direct heating. Designation D 4959-07. West Conshohocken, PA: ASTM International. ______. 2007b. Standard test method for density and unit weight of soil in place by sand cone method. Designation D 1556-07. West Conshohocken, PA: ASTM International. ____. 2007c. Standard test method for particle-size analysis of soils. Designation D 422-63. West Conshohocken, PA: ASTM International. ______. 2008. Standard test methods for determination of water (moisture) content of the soil by the microwave oven heating. Designation D 4643-08. West Conshohocken, PA: ASTM International. _____. 2010a. West Conshohocken, PA. Standard test method for in-place density and water content of soil and soil-aggregate by nuclear methods (shallow depth). Designation D 6938-10. West Conshohocken, PA: ASTM International. _____. 2010b. Standard test methods for laboratory determination of water (moisture) content of soil and rock by mass. Designation D 2216-10. West Conshohocken, PA: ASTM International. _____. 2010c. Standard test methods for liquid limit, plastic limit, and plasticity index of soils. Designation D 4318. West Conshohocken, PA: ASTM International. _____. 2011. Standard practice for classification of soils for engineering purposes (unified soil classification system). Designation D 2487. West Conshohocken, PA: ASTM International. _____. 2012a. Standard test method for bulk specific gravity and density of compacted bituminous mixtures using automatic vacuum sealing method. Designation D 6752. West Conshohocken, PA: ASTM International. ERDC/GSL TR-16-28 48 _____. 2012b. Standard test method for bulk specific gravity and density of non- absorptive compacted bituminous mixtures. Designation D 2726. West Conshohocken, PA: ASTM International. _____. 2012c. Standard test methods for laboratory compaction characteristics of soil using modified effort. Designation D 1557. West Conshohocken, PA: ASTM International. _____. 2013. Standard test method for in-place density (unit weight) and water content of soil using an electromagnetic soil density gauge. Designation D 7830. West Conshohocken, PA: ASTM International. Berney, E. S., IV, and Wahl, R.E. 2008. A rapid soils analysis kit. ERDC/GSL TR-08-3. Vicksburg, MS: U.S. Army Engineer Research and Development Center. Berney, E. S., IV, M. Mejías-Santiago, and J. D. Kyzar. 2013. Non-nuclear alternatives to monitoring moisture-density response in soils. ERDC/GSL TR-13-6. Vicksburg MS: U.S. Army Engineer Research and Development Center. Berney, E. S., IV, Mejías-Santiago, M., and J. Beasley. 2014. Validation tests of a non- nuclear combined asphalt and soil density gauge. ERDC/GSL TR-14-10. Vicksburg MS: U.S. Army Engineer Research and Development Center. Mejías-Santiago, M., E. S. Berney, and C. Bradley. 2013. Evaluation of a non-nuclear soil density gauge on fine-grained soils. ERDC/GSL TR-13- 20. Vicksburg MS: U.S. Army Engineer Research and Development Center. Sebesta, S., C. Estakhri, T. Scullion, and W. Liu. 2006. New technologies for evaluating flexible pavement construction: Year 1 report. FHWA/TX-06/0-4774-1. College Station, TX: Texas Department of Transportation. Transportation Research Board (TRB). 2011. Guide for mechanistic-empirical design of new and rehabilitated pavement structures. Washington DC: National Cooperative Highway Research Program. Troxler Electronic Laboratories, Inc. 2016. Manual of operation and instruction: Troxler Roadreader™ Model 3430 Surface Moisture-Density Gauge. http://www.troxlerlabs.com/Portals/0/Troxler%20Documents/User%20Documents/3430/343 0%20Manual%20of%20Operation%20and%20Instruction%20Edition%201.1%20English.pdf Zhuang, Ziqing. 2011. Effectiveness study of non-nuclear gauge for hot mix asphalt (HMA) pavement construction. University of Nebraska Construction Systems - Dissertations & theses. Paper No. 5. Lincoln NE: University of Nebraska. ERDC/GSL TR-16-28 49 Appendix A: Soil Characterization Data Clay Gravel ERDC/GSL TR-16-28 50 ERDC/GSL TR-16-28 51 Limestone ERDC/GSL TR-16-28 52 ERDC/GSL TR-16-28 53 Red Clayey Sand ERDC/GSL TR-16-28 54 ERDC/GSL TR-16-28 55 Blended Clayey Sand ERDC/GSL TR-16-28 56 ERDC/GSL TR-16-28 57 Low Plasticity Clay ERDC/GSL TR-16-28 58 ERDC/GSL TR-16-28 59 Buckshot Clay ERDC/GSL TR-16-28 60 ERDC/GSL TR-16-28 61 Appendix B: Gauge Comparison Data ERDC/GSL TR-16-28 62 ERDC/GSL TR-16-28 63 ERDC/GSL TR-16-28 64 ERDC/GSL TR-16-28 65 ERDC/GSL TR-16-28 66 ERDC/GSL TR-16-28 67 Asphalt Samples Nuke 1st pos.Nuke 2nd pos.eGauge 1st pos.eGauge 2nd pos. W. Density W. Density W. Density W. Density 1 134 146.1 140.1 2 141.2 147.0 144.1 3 137.2 135.6 136.4 1 140.9 138.9 139.9 140.7 143.5 142.1 2 137.1 143.3 140.2 143.9 138.6 141.3 3 139.3 139.6 139.5 139.8 138 138.9 1 140.6 141.1 140.9 145.5 147.3 146.4 2 143.9 143.4 143.7 143.4 146.2 144.8 3 140.2 140.2 140.2 139.5 144.3 141.9 Nuke 1st pos.Nuke 2nd pos.eGauge 1st pos.eGauge 2nd pos. W. Density W. Density W. Density W. Density 1 135.9 146.1 141.0 2 149.3 149.2 149.3 3 141.8 151.8 146.8 1 139.3 143.3 141.3 140.2 136.7 138.5 2 139.9 143.1 141.5 143.1 142.4 142.8 3 142.1 139.3 140.7 140.3 143.1 141.7 1 144 145.8 144.9 136.9 141.7 139.3 2 142.5 140.8 141.7 145.2 147.7 146.5 3 142.3 143.2 142.8 140.1 140.8 140.5 Nuke 1st pos.Nuke 2nd pos.eGauge 1st pos.eGauge 2nd pos. W. Density W. Density W. Density W. Density 1 126.8 130.0 128.4 2 126.8 132.7 129.8 3 110.3 112.6 111.5 1 134.1 137.1 135.6 134.4 137.7 136.1 2 135.6 136.7 136.2 137.4 137.2 137.3 3 132.7 133.4 133.1 135.7 136.9 136.3 1 136.5 137.3 136.9 138.3 138.4 138.4 2 137.3 137.5 137.4 140.8 138.5 139.7 3 134.7 135.5 135.1 137.9 138.8 138.4 1 136.4 135.3 135.9 138.1 137.5 137.8 2 136.1 136.3 136.2 136.9 136.8 136.9 3 134.4 136.3 135.4 135.1 136.8 136.0 Values that have been calculated, all other values not in Bold are raw readings from field/laboratory tests 6" DP-Deep Sample 4" 2" Backscatter/ Backscatter/ 2" 4" Backscatter/ 2" 4" RT-Rough Texture ST-Smooth Texture Sample Type Depth Position Average W. Density Average W. Density Sample Type Depth Position Average W. Density Average W. Density Sample Type Depth Position Average W. Density Average W. Density ERDC/GSL TR-16-28 68 Asphalt Samples CASE 1 CASE 3 CASE 1 CASE 3 SSD Core-Lok W. Density W. Density W. Density W. Density B. Density B. Density 1 138.6 141.5 140.1 142.4 145.3 143.9 0.0 2 141.6 139.1 140.4 145.4 142.9 144.2 0.0 3 137.5 137.1 137.3 141.3 140.9 141.1 0.0 1 Calibration value -138.6 0.0 2 0.0 3 0.0 1 145.6 144.5 145.1 2 147.1 146.2 146.7 3 144.9 142.5 143.7 CASE 1 CASE 3 CASE 1 CASE 3 SSD Core-Lok W. Density W. Density W. Density W. Density B. Density B. Density 1 143.4 141.6 142.5 142.9 141.1 142.0 0.0 2 146.7 147.3 147.0 146.2 146.8 146.5 0.0 3 149.5 148.7 149.1 149.0 148.2 148.6 0.0 1 Calibration value -143.4 0.0 2 0.0 3 0.0 1 145.8 145.3 145.6 2 144.7 144.5 144.6 3 145.3 144.9 145.1 CASE 1 CASE 3 CASE 1 CASE 3 SSD Core-Lok W. Density W. Density W. Density W. Density B. Density B. Density 1 132.5 132.8 132.7 141.8 142.1 142.0 141.8 2 135.6 134.4 135.0 144.9 143.7 144.3 142.1 3 133.3 133.9 133.6 142.6 143.2 142.9 141.8 1 Calibration value 9.3 141.8 2 142.1 3 141.8 1 0.0 2 0.0 3 0.0 1 141.9 141.1 141.5 2 141.4 140.8 141.1 3 141.6 141.1 141.4 Values that have been calculated, all other values not in Bold are raw readings from field/laboratory tests Average W. Density Average W. Density Average B. Density Average W. Density Average W. Density Average B. Density Average W. Density Average W. Density Average B. Density Sample Type Depth Position DP-Deep Sample Backscatter/ 2" 4" 6" Sample Type Depth Position ST-Smooth Texture Backscatter/ 2" 4" Sample Type Depth Position RT-Rough Texture Backscatter/ 2" 4" REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY) November 2016 2. REPORT TYPE Final report 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE Validation Testing of Non-Nuclear Alternatives to Measuring Soil Density 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Ernest S. Berney IV, Mariely Mejías-Santiago, and Matthew D. Norris 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER U.S. Army Engineer Research and Development Center Geotechnical and Structures Laboratory 3909 Halls Ferry Road Vicksburg, MS 39180-6199 ERDC/GSL TR-16-28 9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S) Headquarters, Air Force Civil Engineering Center Tyndall Air Force Base, FL 32403-5319 11. SPONSOR/MONITOR’S REPORT NUMBER(S) 12. DISTRIBUTION / AVAILABILITY STATEMENT Approved for public release; distribution is unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT During 2015, researchers with the U.S. Army Engineer Research and Development Center (ERDC) validated the effectiveness of the TransTech Combined Asphalt Soil Evaluator (CASE) and the Troxler eGauge as suitable replacements for nuclear density gauge (NDG) technology. Comparisons of soil dry density and moisture content were made between the gauges for six distinct soil types at varying densities and moisture contents. The CASE unit was calibrated using the Sand Cone and hot-plate moisture content prior to its correlation to the NDG; the eGauge was used in its shipped configuration without calibration. Results of both devices were compared to the NDG and core samples to capture asphalt density. Full-scale test sections were constructed for the soil evaluations ranging from crushed limestone to fat clays. Results showed that wet and dry densities obtained with the eGauge very closely matched those of the NDG, but the accuracy of the measured moisture contents was lower. The CASE unit’s calibrated accuracy to the NDG moisture content was excellent, but its wet and dry density accuracies were much lower than the eGauge. Based on the ERDC findings, the eGauge is recommended as the best replacement for the NDG for wet/dry density measurements and requires no calibration or transport/licensing restrictions. 15. SUBJECT TERMS Soils – Density Soil moisture – Measurement – Instruments Soils – Testing Asphalt – Testing 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF RESPONSIBLE PERSON a. REPORT Unclassified b. ABSTRACT Unclassified c. THIS PAGE Unclassified 77 19b. TELEPHONE NUMBER (include area code) Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. 239.18 Troxler 4540 - for SOILS only 2/25/2021 Test Site Graniterock Wilson Quarry, Aromas, CA Test Probe Dry Moisture Oven Dried Wet wet density Site*Gauge Depth (in)Density (pcf)%Moisture delta Density (pcf)new/old delta 1 New 4540 8 116.7 14.3 133.4 1 New 4540 6 116.4 13.7 132.3 1 New 4540 4 114.7 13.7 130.4 1 Old CPN 6456 8 117.6 12.1 131.8 1.6 1 Old CPN 6456 6 117.1 11.3 130.3 2.0 1 Old CPN 6456 4 115.6 12.1 129.6 0.8 2 New 4540 8 112.2 16.8 3.7 131.0 2 New 4540 6 115.3 15.8 2.7 133.5 2 New 4540 4 113.9 16.1 3 132.2 2 Old CPN 6456 8 116.7 12.6 -0.5 131.4 -0.4 2 Old CPN 6456 6 117.6 13.3 0.2 133.2 0.3 2 Old CPN 6456 4 117.9 13.5 0.4 133.8 -1.6 * - used same hole for all 6 tests at each site Average Wet Density 131.9 Oven Dried Moisture at Test Site #2 = 13.1 Other Notes: 1 Timeframe for testing - 4 min warm up 2 min standard count 2 min count (can vary) 5 sec moisture 2 Separate Standard for each different soil type for the day 3 Warm up and standard count every morning Summary: 1 Wet density is VERY consistent - maximum variance from average is between 0.3 and 2.3 pcf for all tests 2 Moisture difference between gauges are consistent (about 1.6 to 2.4% and 2.5 to 4.2% off for sites 1 and 2) 3 Moisture difference between gauge and oven dried moisture is repeatable and not too far off 4 Dry Density between gages is very close to what I'd expect at the site (having already done over 50 tests) 5 Dry density within 1pcf on Site 1 and between 2.3 and 4.5 off on site 2 - primarily due to moisture delta - 1 - EGauge Combo FAQ, rev4 EGauge Combo Frequently Asked Questions 1. As far as licensing, is it verified that these gauges do not require any licensing for storage/use in any states? No radioactive materials license is required anywhere in the USA for the new EGauge Combo, model 4540. Here is a link to official documentation on the NRC web site: https://www.nrc.gov/docs/ML2032/ML20328A141.pdf. 2. What is the nuclear source(s) in these gauges? There is a Cesium-137 source (90 microcuries [3.33 MBq]). The EGauge Combo is a nuclear density gauge – a license exempt nuclear density gauge. The density system is calibrated on the same standards as the licensed nuclear density gauges and is help to the same accuracy standards in this process. 3. What does Troxler’s maintenance and calibration service include? Annual Calibration/Maintenance includes:  A NIST-traceable gauge calibration  Electronic system analysis and adjustment  Full mechanical inspection and service  Software updates (as needed)  Maintenance items replaced (gaskets and seals)  Cleaning inside and out 4. Are there still shipping restrictions with FedEx (i.e., cargo only, hazardous goods)? There are no shipping restrictions or hassles! Troxler ships the EGauge via regular FedEx Ground. The hazmat category of Excepted package is much less restrictive. 5. What is the lifespan of the EGauge? With proper maintenance, the lifespan of the EGauge is approximately 30 years. The source will need to be replaced approximately every 10 years due to the low activity. Estimated source replacement cost: ~$1500. 6. With the need for a different gauge to determine moisture, what are the costs projected for maintenance and calibration per year? No extra cost for routine maintenance and calibration of the moisture probe. - 2 - EGauge Combo FAQ, rev4 7. Have you performed a cost life cycle analysis between your EGauge and a normal Troxler gauge? The EGauge will have a lower lifecycle cost. However, the cost differential is variable based on following:  No licensing fees – Save approximately $2000/year!  No Radiation Safety Training Certification – Save $179 each!  No reciprocity – Save approximately $1000/year!  No Leak Testing – Save approximately $24 each!  No TLD Monitoring Badges – Save $100/year per tech! In addition, you will realize the following imputed cost savings:  No inspections by a licensing agency.  No limitations on use.  No special storage required. 8. How does the moisture probe work? The EGauge is a breakthrough product because it is a license exempt nuclear density gauge.  Density is measured via a nuclear source.  Moisture is measured via electromagnetic technology. === Density: The EGauge yields matching density measurements to those of a traditional nuclear gauge, like the 3440, because it is a nuclear gauge -- a license exempt nuclear gauge. Please download a study from the Army Corps of Engineers, Validation Testing of Non-Nuclear Alternatives to Measuring Soil Density, at https://www.troxlerlabs.com/Portals/0/Troxler%20Documents/Other%20Documents/USArmyEGau geReport.pdf. This report finds accuracy to be virtually identical to that of traditional nuclear gauge. Regression analysis showed the EGauge to track one-to-one with traditional nuclear gauges. === Moisture: A useful technical bulletin, Troxler EGauge Moisture Probe Measurements, available upon request, outlines the two ways to take moisture probe measurements:  Moisture Offset – Simplest and most common method.  Moisture Probe Calibration – Creates a new moisture calibration profile, which is then stored for later use. 9. Is there no standard reference block for this gauge? The standard count is performed on the test material surface. This material serves as the standard block for the EGauge. - 3 - EGauge Combo FAQ, rev4 10. What’s Included? Everything! The EGauge Combo is turnkey. You get: • Moisture Probe (wireless Bluetooth communication) • Auto Depth • GPS • Remote Keypad • Data Storage (1,000 readings) • External Beeper • LED Charger Indicator • Bluetooth • USB Port • Serial Port • Case with wheels and extendable handle 1 Evaluation of Non-regulated Portable Moisture Density Gauge March 2022 Melissa Serio, Earthwork Engineer Construction & Materials Bureau SP&R Part II, 775 Project # 19-SPR0-007 2 Technical Report Documentation Page Form DOT F 1700.7 (8-72) Reproduction of completed page authorized 1. Report No. 19-SPR0-007 2. Government Accession No. 3. Recipient's Catalog No. 4. Title and Subtitle Evaluation of Non-regulated Portable Moisture Density Gauge 5. Report Date March 2022 6. Performing Organization Code 7. Author(s) Melissa Serio 8. Performing Organization Report No. 19-SPR0-007 9. Performing Organization Name and Address Construction and Materials Bureau Iowa Department of Transportation 800 Lincoln Way Ames, Iowa 50010 10. Work Unit No. (TRAIS) 11. Contract or Grant No. 12. Sponsoring Agency Name and Address Iowa Department of Transportation Federal Highway Administration 800 Lincoln Way 1200 New Jersey Avenue, SE Ames, Iowa 50010 Washington, DC 20590 13. Type of Report and Period Covered Final Report 14. Sponsoring Agency Code 19-SPR0-007 15. Supplementary Notes 16. Abstract Standard portable nuclear moisture-density gauges are very accurate and easy to operate for determining density and moisture content of soils as well as other construction materials. Unfortunately, the size of the radioactive sources used in the standard nuclear gauges are such that they are regulated by the Nuclear Regulatory Commission and in Iowa, the Department of Public Health. Recently, a new portable gauge was developed by Troxler called the EGauge that measures wet density. The EGauge uses the technology of a nuclear gauge, but it has a low radioactive source and is exempt from licensing. The non-regulated EGauge is paired with the use of a moisture probe to measure moisture content. The Iowa DOT currently has ten portable nuclear gauges that are used for quality assurance (QA) testing on embankment construction with moisture and density control or moisture control only. If the new EGauge is sufficiently accurate, they could be made much more accessible to the construction and materials staff monitoring contractors’ quality control (QC) testing. Based on the licensing exemption, there could be a quantifiable savings with the new gauges and more importantly a reduced risk of injury or death from radiation exposure. Additionally, if the new type of gauge is allowed, there would be a savings and reduced risk for contractors performing QC testing. The study used comparative tests between the EGauge and the standard nuclear gauge on grading projects. Samples were collected to compare wet density, dry density, and moisture content using the different gauges. A recommendation was made to allow the use of the non-regulated nuclear gauge for wet density only and Materials IM 204, Appendix A was revised to allow for low activity nuclear gauges, such as the Troxler EGauge, as an acceptable test method for wet density. Based on the inconsistency in differences (i.e. moisture offset) for the same material and the low R-square value comparing the EGauge moisture probe to oven-dried moisture content, it was not recommended to use the EGauge moisture probe. 17. Key Word nuclear gauges, wet density, dry density, moisture content, soils 18. Distribution Statement No restrictions 19. Security Classification. (of this report) Unclassified 20. Security Classification (of this page) Unclassified 21. No. of Pages 12 22. Price N/A 3 Disclaimer Notice The contents of this report reflect the views of the authors, who are responsible for the facts and the accuracy of the information presented herein. The opinions, findings, and conclusions expressed in this publication are those of the author and not necessarily those of the Iowa Department of Transportation or the United States Department of Transportation, Federal Highway Administration. The sponsors assume no liability for the contents or use of the information contained in this document. This report does not constitute a standard, specification, or regulation. The sponsors do not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objectives of the document. Nondiscrimination Statement Federal and state laws prohibit employment and/or public accommodation discrimination on the basis of age, color, creed, disability, gender identity, national origin, pregnancy, race, religion, sex, sexual orientation or veteran’s status. If you believe you have been discriminated against, please contact the Iowa Civil Rights Commission at 800-457-4416 or Iowa Department of Transportation's affirmative action officer. If you need accommodations because of a disability to access the Iowa Department of Transportation’s services, contact the agency's affirmative action officer at 800-262-0003. 4 Background Standard portable nuclear moisture-density gauges are very accurate and easy to operate for determining density and moisture content of soils as well as other construction materials. Unfortunately, the size of the radioactive sources used in the standard nuclear gauges are such that they are regulated by the Nuclear Regulatory Commission and in Iowa, the Department of Public Health. The regulations are intended to prevent accidental exposure of people to radiation from misuse of the gauge. However, with the regulations are added time and money for licensing, training, recordkeeping, and security measures. Recently, a new portable gauge was developed by Troxler called the EGauge that measures wet density. The EGauge uses the technology of a nuclear gauge, but it has a low radioactive source and is exempt from licensing. The non-regulated EGauge is paired with the use of a moisture probe to measure moisture content. The Iowa DOT currently has ten portable nuclear gauges that are used for quality assurance (QA) testing on embankment construction with moisture and density control or moisture control only. If the new EGauge is sufficiently accurate, they could be made much more accessible to the construction and materials staff monitoring contractors’ quality control (QC) testing. Based on the licensing exemption, there could be a quantifiable savings with the new gauges and more importantly a reduced risk of injury or death from radiation exposure. Additionally, if the new type of gauge is allowed, there would be a savings and reduced risk for contractors performing QC testing. Evaluation Procedure Tasks completed were as follows: 1. Purchase two Troxler Model 4590 EGauges including the 6760 Moisture Probe (Figure 1). 2. Discuss and decide with the Technical Advisory Committee (TAC) members what locations and how many locations should be tested. 3. Run comparative tests between the EGauge and the standard nuclear gauge on grading projects. 5 Figure 1: Troxler Model 4590 EGauge (back) and 6760 Moisture Probe (front) The TAC was comprised of the following individuals: • Rod Graven, Construction & Materials Bureau • Jeff DeVries, Construction & Materials Bureau • Stephen Upchurch, Construction & Materials Bureau • Melissa Serio, Construction & Materials Bureau • Roger Boulet, District 6 Materials • Mark Dutra, District 6 Materials • Alex Crosgrove, District 3 Materials Preliminary data was collected near the Ames DOT complex in August 2019 and in September and October 2019 at the Polk County – I-80 and IA 141 construction sites. At both locations, wet density, dry density, and moisture content were measured using at least one of the Troxler EGauges and a DOT 6 Humboldt nuclear gauge. Additionally, at the Polk County construction site, data was collected using a gauge operated by a consultant performing QC for the contractor. The TAC met in 2021 to develop a formal testing plan to compare Troxler EGauge with standard nuclear gauges. The testing plan included the following comparison testing: • Use at least one EGauge and moisture probes at a testing location • Use a standard nuclear gauge • Collect wet density, dry density, and moisture content using the gauges • Collect moisture samples to determine oven-dried moisture content The first testing site was at the Ames DOT facility on April 22, 2021. Troxler sent representatives onsite to assist with this testing. Data was collected at three locations. The remainder of comparison testing was completed during the 2021 construction season at the following locations in central Iowa: • Boone County, IA 17, 7/2/21 • Polk County, US 69, 8/13/21 • Story County, 13th Street in Ames, 10/8/21 At these three construction sites, data was collected at eight locations per each site. Results Moisture content and wet density data collected from sites noted in the “Evaluation Procedure” section was compiled as follows: • Wet Density: 35 locations of comparison testing (67 data points) o 2 non-regulated EGauges compared to 1 nuclear gauge (54 data points) o 1 non-regulated EGauge compared to 2 nuclear gauges (13 data points) • Moisture Content: 27 locations (67 data points) 7 o 2 non-regulated EGauges compared to 1 nuclear gauge and 1 oven-dried sample (54 data points) o 1 non-regulated EGauge compared to 2 nuclear gauges (13 data points) Figure 2 shows a comparison of moisture data using the EGauge moisture probe versus corresponding oven-dried moisture contents. Additionally in this figure are shown a 1:1 line to illustrate if the EGauge provided the same readings as determined from oven-dried samples and 1:1 lines with the current tolerances (-1.5% to +1.5%) from Materials IM 216 for moisture content. Figure 3 shows EGauge moisture probe data versus both oven-dried and nuclear gauge moisture contents. Figure 2: EGauge moisture probe data versus oven-dried moisture content (%) Figures 2 and 3 show low R-squared values (0.4666 for oven-dried and 0.0074 for nuclear gauge), which indicate the data does not show a strong fit to the regression lines. y = 2.1218x -8.7968 R² = 0.4666 5 10 15 20 25 30 35 40 45 50 5 7 9 11 13 15 17 19 21 eG a u g e % M o i s t u r e Oven Dried % Moisture eGauge versus oven dried 1:1 line 1:1 line + 1.5% 1:1 line - 1.5% Linear (eGauge versus oven dried) Linear (1:1 line) Linear (1:1 line + 1.5%) Linear (1:1 line - 1.5%) 8 Figure 3: EGauge moisture probe data versus nuclear gauge and oven-dried moisture content (%) To adjust the EGauge moisture probe values to match a specific soil more closely, Troxler recommends the use of a moisture offset. To determine a moisture offset, readings would be taken using the EGauge moisture probe at three to five locations and then compared to oven-dried samples. This process was performed at three of the construction sites for the different soil types observed. Differences between EGauge moisture probe values and oven-dried samples were as follows: • Boone County: o Area 1: 7.6% to 9.6% higher o Area 2: 2.1% lower to 4.5% higher • Polk County: o Area 1: 13.5 to 22.8% higher o Area 2: 0.3% higher to 4.3% lower • Story County: o 5.9% to 16.9% higher As shown, these differences (i.e. moisture offset) for the same soil type varied by 2% (comparing 7.6% to 9.6%) to 11% comparing (5.9% to 16.9%). Figure 4 shows a comparison of EGauge wet densities versus the corresponding standard nuclear gauge wet densities. Additionally on this figure is shown a 1:1 line to illustrate if the EGauge provided the y = 0.3267x + 16.175 R² = 0.0074 y = 2.1218x -8.7968 R² = 0.4666 0 5 10 15 20 25 30 35 40 45 50 0 5 10 15 20 25 eG a u g e % M o i s t u r e Nuclear Gauge % Moisture or Oven Dried % Moisture eGauge vs. Nuclear Gauge eGauge vs. Oven Dried Linear (eGauge vs. Nuclear Gauge) Linear (eGauge vs. Oven Dried) 9 same readings as the nuclear gauge. Along with the 1:1 line, the current tolerances (-2 pcf and +2 pcf) from Materials IM 216 for wet density are shown and proposed expanded tolerances (-5 pcf and +5 pcf). Figure 4: EGauge wet density versus nuclear gauge wet density (pcf) The data comparing wet densities had a high R-squared value of 0.9402, which indicates a strong fit to the regression line. Of the 67 data points, the following is a breakdown of tests (comparing EGauge wet density to nuclear gauge wet density) that would fall within the current tolerances from Materials IM 216 and proposed expanded tolerances: • Current tolerance (+/- 2 pcf): 32 out of 67 = 48% • Expanded tolerance (+/- 3 pcf): 49 out of 67 = 73% • Expanded tolerance (+/- 4 pcf): 56 out of 67 = 84% • Expanded tolerance (+/- 5 pcf): 63 out of 67 = 94% Dry densities were not plotted because dry density is calculated using wet density and moisture content. y = 0.9408x + 6.3039 R² = 0.9402 90 100 110 120 130 140 150 160 90.0 100.0 110.0 120.0 130.0 140.0 150.0 EG a u g e W e t D e n s i t y Nuclear Gauge Wet Density WD comparison 1:1 line 1:1 line + 2 pcf 1:1 line - 2 pcf 1:1 line + 5 pcf 1:1 line - 5 pcf Linear (WD comparison) Linear (1:1 line) Linear (1:1 line + 2 pcf) Linear (1:1 line - 2 pcf) Linear (1:1 line + 5 pcf) Linear (1:1 line - 5 pcf) 10 As part of our review of the EGauge, we considered additional data collected by the US Army Corps of Engineers. Figure 5 shows EGauge densities compared to densities collected using a nuclear gauge. On this figure, we added a 1:1 line to illustrate if the EGauge provided the same readings as the nuclear gauge, a 1:1 line with the current tolerances (-2 pcf and +2 pcf) from Materials IM 216 for wet density, and a 1:1 line with possible expanded tolerances (-5 pcf and +5 pcf). The Army Corps data for wet density showed a high R-squared value of 0.9367, which was very similar to our data. Figure 5: Army Corps of Engineers data comparing EGauge to nuclear gauge densities Recommendations and Implementation Information was presented to the District Materials Engineers (DMEs) at their November 17, 2021, meeting. A recommendation was made to the DMEs and accepted by the DMEs to allow the use of the non-regulated nuclear gauge for wet density only. As a result, Materials IM 204, Appendix A was revised (effective April 19, 2022) so ASTM D8167 for low activity nuclear gauges, such as the Troxler EGauge, is an acceptable test method for wet density. This revision is shown in Figure 6. Additionally, it was recommended and accepted to keep the current tolerances in Material IM 216 for wet density as -2 pcf to +2 pcf. It was discussed that if this becomes an issue, then the tolerances will be re-evaluated. 11 Figure 6: Materials IM 204, Appendix A (Effective April 19, 2022) 12 Allowing the use of a non-regulated gauge, such as the EGauge, for determining wet density of soil provides an additional way for the Iowa DOT, testing company, contractor, or local public agency to test soils. As noted in the Background section, this type of equipment may be used as an alternative to the standard nuclear gauge. Based on the inconsistency in differences (i.e. moisture offset) for the same material and the low R- square value comparing the EGauge moisture probe to oven-dried moisture content, we did not recommend allowing the use of the EGauge moisture probe. As shown in Materials IM 204, Appendix A (Figure 6), moisture contents shall be determined by Materials IM 335, which allows for use of direct heat (e.g. hot plate, etc.), microwave, or drying oven. References Berney, E.S., IV, Mejias-Santiago, M, and Norris, M.D. November 2016. Validation Testing of Non- Nuclear Alternatives to Measuring Soil Density. ERDC/GSL TR-16-28. US Army Corps of Engineers, Engineer Research and Development Center. Retrieved from: https://erdc- library.erdc.dren.mil/jspui/bitstream/11681/20381/1/ERDC-GSL%20TR-16-28.pdf