Density Gauge Research Articles

Non-destructive compaction evaluation and comparison of different asphalt centerline longitudinal joints

Longitudinal joint quality is critical to the service life of asphalt pavements. Maintaining failed joints of asphalt pavements is a challenge for many highway agencies. Long-term performance issues of flexible pavements may result from a poorly constructed joint; the low-density joint can prematurely deteriorate an otherwise sound pavement. The longitudinal joint is built using different geometries, rolling patterns, and construction techniques, all involving risk in achieving a well-compacted joint. Conventional quality control (QC) and quality assurance (QA) testing (using cores or density gauges) provide limited coverage due to their spot-test nature. Using conventional QC/QA methods involves the risk of accepting a poorly constructed longitudinal joint at the time of construction. This study used continuous data from the non-destructive dielectric profiling system (DPS) to identify compaction ability differences between the various joint types and construction techniques. The analysis suggests avoiding constructing an unconfined joint when possible. Percent within limits (PWL) analysis shows that any joint geometry could produce minimal compaction differences between the joint and the mat. However, if an unconfined joint needs to be constructed, a portion of the unconfined joint should be cut back before paving the adjacent lane. Such a cutback technique can result in better unconfined joint compaction. Further, PWL results showed that using a smaller subsection/sublot can isolate local compaction issues; a 100 ft sublot length is preferable for PWL analysis when utilizing DPS for compaction evaluation.

Repeatability and Reproducibility of Pavement Density Profiling Systems

The work conducted in this study was designed to establish achievable testing tolerances for non-destructive pavement density measurements using Density Profiling Systems (DPSs). Nine and six sensors were used to determine the precision of repeatability and reproducibility in the laboratory and the field, respectively. A minimum of six sensors (considered in this study as independent laboratories) were needed to comply with the minimum number of participants required in the current ASTM standard practice (ASTM E691). The methodology included the development of laboratory precision evaluation with a total of nine sensors and two different mixtures (9.5 mm fine-graded mix, 19.0 mm coarse-graded mix) compacted at four density levels (97%, 94%, 91%, and 88% of Gmm). For the field portion of this study, pavement sections built at the National Center for Asphalt Technology (NCAT) Test Track in 2021 served as experimental variables. These sections were built with fine-graded asphalt mixtures and open-graded mixes as wearing courses. Additionally, the pavement sections included three underlying materials: new asphalt (binder layer), milled asphalt surface, and granular base, with thicknesses ranging from 3.8 to 13.9 cm. Density profile testing was conducted at two locations: within the mat (center of the lane) and along the joint. Computed precision statements regarding dielectric values within and between laboratories were about double for field results compared to laboratory results. However, when converted to density, the statements were significantly below the reported statements for Bulk Specific Gravity and Vacuum Sealing in the laboratory and Nuclear and Electromagnetic density gauges in the field.

An Artificial Neural Network-Based Approach to Improve Non-Destructive Asphalt Pavement Density Measurement with an Electrical Density Gauge

Asphalt pavement density can be measured using either a destructive or a non-destructive method. The destructive method offers high measurement accuracy but causes damage to the pavement and is inefficient. In contrast, the non-destructive method is highly efficient without damaging the pavement, but its accuracy is not as good as that of the destructive method. Among the devices for non-destructive measurement, the nuclear density gauge (NDG) is the most accurate, but radiation in the device is a serious hazard. The electrical density gauge (EDG), while safer and more convenient to use, is affected by the factors other than density, such as temperature and moisture of the environment. To enhance its accuracy by minimizing or eliminating those non-density factors, an original approach based on artificial neural networks (ANNs) is proposed. Density readings, temperature, and moisture obtained by the EDG are the inputs, and the corresponding densities obtained by the NDG are the outputs to train the ANN models through Levenberg-Marquardt, Bayesian regularization, and Scaled Conjugate Gradient algorithms. Results indicate that the ANN models trained greatly improve the measurement accuracy of the electrical density gauge.

Measuring the In Situ Density and Moisture Content of Filtered Tailings Using an Electrical Density Gauge

Due to the logistical challenges associated with using nuclear densitometers at remote sites, the industry is seeking an alternative method to determine the in situ density and moisture content during the construction of filtered tailings facilities. This study aims to investigate the impact of salinity on soil electrical properties and evaluate the feasibility of using an electrical density gauge (EDG) to measure the in situ density and moisture content of saline filtered tailings. The results indicate a dependence of electrical measurements on salinity. To develop procedures for soil calibration models of filtered tailings, standard Proctor tests were first conducted using Devon silt. These procedures were then applied to the filtered tailings to establish correlations between electrical properties (dielectric constant, impedance, capacitance-to-resistance ratio) and physical properties (density and moisture content) at varying salinities. It is suggested to build the soil calibration model using an EDG within a water content range of 10% to 18%. Furthermore, the effectiveness of the developed calibration models has been validated, demonstrating the applicability of the EDG instrument for filtered tailings in a saline environment. However, applying the salinity correction is crucial when the sample has a considerably different salinity than the calibration model.

Novel non-nuclear methodology for coarse granular soil compaction control: the Sherbrooke Method

The nuclear density gauge (NDG) is the most established device for compaction control. Several studies have proposed alternatives to it, but none have been widely adopted for a variety of reasons. This paper presents the Sherbrooke Method (SM), which involves the use of innocuous, user-friendly, and low-cost devices. It uses frequency domain reflectometry (FDR) sensors to obtain bulk density and gravimetric water content. In this research, 442 field test comparisons between the SM and the NDG device, and 117 between the SM and physical tests were obtained at sites where a type of well-graded gravel (MG 20 in Quebec) was used. The FDR technology showed promising results, with good ability to predict bulk density and gravimetric water content. Moreover, the method presented low complexity of execution and the data emitted by the probe can be obtained in 1 minute. Nowadays, the total lapse of time from setting up the device to the final response (of 3 tests) is approximately 20 minutes. The SM also presents a bulk density precision comparable to that of other devices reported in the technical literature.

In-situ spot test measurements and ICMVs for asphalt pavement: lack of correlations and the effect of underlying support

ABSTRACT The main aim of this paper is to analyse the performance of different intelligent compaction measurement values (ICMVs) and compare them with spot test measurements for asphalt pavement. To accomplish this, a two-layer asphalt testbed was constructed using an instrumented double-drum roller. All ICMVs [compaction meter value ( C M V ), compaction control value ( C C V ), roller-integrated stiffness ( k b ), and vibratory modulus ( E V I B )] were calculated using the same accelerometer data collected during the construction of the asphalt testbed. The analysis of ICMV data showed a strong correlation between k b and E V I B , while C M V and C C V demonstrated a strong correlation only when double jump of the roller drum did not occur. Further, none of the ICMVs recorded during the last roller pass of asphalt compaction showed an acceptable correlation with asphalt densities [measured using a non-nuclear density gauge (NNDG)], mainly due to the influences of the underlying support and asphalt temperature on ICMVs. A correction method to decouple the influence of underlying support on E V I B was developed and validated using existing data from the literature. The applicability of this method for different field scenarios was demonstrated using numerical modelling.

A comparative analysis of merging strategies for satellite precipitation estimates and ground observations over Chinese mainland

Satellite precipitation estimates are attractive for providing spatially continuous precipitation measurement on the global scale, but improvements in accuracy are still needed relative to the point-scale gauge observations. In this study, two integration frameworks named Geographical Differential Analysis (GDA) and Geographical Ratio Analysis (GRA) combined with two interpolation techniques named Ordinary Kriging (OK) and Inverse Distance Weighting (IDW) were adopted to merge the satellite precipitation with ground-based observations. The Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) research product was merged with the ground rain gauges derived from CGDPA (China Gauge-based Daily Precipitation Analysis) at a monthly scale over the Chinese mainland from 2011 to 2015, and the merged precipitation products were evaluated by 10-fold cross-validation. Results showed that the merged precipitation products based on the GDA integration framework had significant improvements relative to the original TMPA. Moreover, the method based on GDA combined with Ordinary Kriging (GDA-OK) delivered better performances compared to the GDA-IDW (method based on GDA combined with Inverse Distance Weighting) since the OK considers the global spatial correlation. However, the GRA-based merged precipitation products had systematic underestimations over Chinese mainland during all seasons and were not recommended for satellite-gauge precipitation merging over the large spatial scale of Chinese mainland. In addition, we found that the OK is quite sensitive to the density gauge network, the shrinkage of the number of rain gauges may result in great uncertainties and errors in the OK interpolation technique.

Some Metal Oxide-Natural Rubber Composites for Gamma- and Low-Energy X-Ray Radiation Shielding

This work studied protective material consisting of several metal oxide composites (Pb3O4, WO3, SnO2, and Bi2O3)-natural rubber (NR) for X-ray and gamma-ray shielding. The composites were prepared through open milling and vulcanization processes and further characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), rheometry analysis, and density gauge. The attenuation coefficient of the sample was investigated using X-ray generators with voltages ranging from 50 to 140 kV and gamma-ray energies ranging and 356 to 1250 keV, respectively. The experimental results show that the linear attenuation coefficient of NR filled with metal oxides was significantly improved compared to pure NR. For gamma-ray 661 keV, the HVL of NR decreased from 9.0 cm to between 4.4 - 6.2 cm after it was filled with metal oxides. The Bi2O3-NR is the best suitable material for gamma-ray attenuation, followed by Pb3O4-NR, WO3-NR, and SnO2-NR. Meanwhile, for x-rays, the HVL of NR decreased from 2.0 cm to between 0.17 -0.31 cm after it was filled with metal oxides. The proposed metal oxide-NR composites can be appropriate as a flexible protective material for manufacturing wearable radiation shielding products such as gloves, aprons, rubber underwear, and other wearable materials.

New Method for Quality Assurance of Asphalt Pavements Using a Low-Activity Nuclear Density Gauge

A method was developed for measuring the density of finished asphalt pavement layers using a low-activity nuclear density gauge (LNDG) that is exempt from licensing and other nuclear regulatory burdens in the United States. The gauge using this method, LNDG/TM, requires operating in transmission mode—inserting the gamma-ray source at 0.5 in. (12.5 mm) into the asphalt layer. This method is fast and less destructive than the industry-accepted core-extraction (CE) method—CE followed by laboratory density measurement. This paper presents the measurement principles, method, and properties of this gauge. For evaluating the method, several laboratory and field studies were conducted in North Carolina, USA. For surface course measurements, the repeatability standard deviation of the measurement was 0.3 lb/ft3 (5 kg/m3), and the reproducibility standard deviation was 0.5 lb/ft3 (8 kg/m3). The measurement sensitivity is similar to that of the CE method. The depth of measurement of the gauge is about 2 in. (50 mm). For layers with mean texture depth from 0.5 to 1 mm, the density error is less than 2 lb/ft3 (32 kg/m3). The LNDG/TM requires a density correlation method to provide accurate measurements. Following this method, LNDG/TM density measurements showed a good correlation (correlation coefficient = 0.9) and agreement (root mean square error = 1.3 lb/ft3 [21 kg/m3]) to that using the CE method. These findings indicate that LNDG/TM is a promising alternative to the CE method and has the advantage of testing more locations for acceptance testing.

Compaction Quality Assurance Specifications of Unbound Materials

Compaction quality control/assurance of unbound geomaterials is one of the crucial components in pavement and embankment construction to ensure their performance, stability, and sustainability. Conventional density-based methods such as nuclear density gauge to determine the compaction quality have been widely used due to the straightforward relationship between the readings and targeted material property. Recent modifications in construction standards and the introduction of the Mechanistic-Empirical Pavement Design Guide have inspired a growing interest in developing and implementing strength/stiffness-based compaction control quality assurance (QA) specifications. Numerous studies have been dedicated to investigating the efficiency and effectiveness of the stiffness-based compaction QA tools. This paper presents a comprehensive review of the recent compaction QA relevant literature and surveys. Findings of different approaches for studying QA devices, and the main results of the existing models, experiments, and engineering practices were summarized. Several in situ spot QA technologies, including the latest compaction QA technologies [e.g., the lightweight deflectometer (LWD)], were highlighted, and their efficiency and effectiveness were compared. The review also summarized the intercorrelations between different devices, the correlations between in situ QA device readings and mechanical properties of unbound material, findings of the numerical simulations, and case studies and current practices using different QA tools. The recommendations for future research needs and practical implementations were identified and discussed.

Prediction of Soil Moisture Content through Photographs of Cobalt Chloride Filter Paper in Contact with Soil Specimens

Abstract Measured soil moisture content is a useful geotechnical engineering property for a variety of analyses. The laboratory determination of soil moisture content can be time consuming, labor intensive, or both; the field determination of soil moisture content may require additional certification, as associated with the use of the nuclear density gauge. The objective of this research was to identify a method that could be used to determine the soil moisture content without the aforementioned disadvantages. This objective was achieved through the use of cobalt chloride filter paper being placed into contact with the soil. The cobalt chloride filter paper changes color in the presence of moisture (a blue color when the paper is dry and a pink color when the paper is wet). A membrane separated the cobalt chloride paper and the surface of soil specimens (kaolinite, bentonite, Donna Fill, and a silty sand) to prevent cobalt chloride migration. The soil specimens were prepared at different moisture contents, and photography-based hue values were determined for each soil/cobalt chloride filter paper pair at given time intervals. Linear correlations were observed to exist between the soil moisture content and the slope of the linear portion of the hue-time relationship for all of the investigated soil types. The coefficients of determination (R2) ranged from .91 to .99. All soils showed a strong positive linear relationship between the slope of the cobalt chloride hue and soil moisture content. This use of hue may provide a rapid determination of in situ soil moisture content.

Derivation and implementation of the optical rotation tensor for chiral crystals.

This paper reports the derivation and implementation of the electric dipole-magnetic dipole and electric dipole-electric quadrupole polarizability tensors at the density functional theory level with periodic boundary conditions (DFT-PBC). These tensors are combined to evaluate the Buckingham/Dunn tensor that describes the optical rotation (OR) in oriented chiral systems. We describe several aspects of the derivation of the equations and present test calculations that verify the correctness of the tensor formulation and their implementation. The results show that the full OR tensor is completely origin invariant as for molecules and that PBC calculations match molecular cluster calculations on 1D chains. A preliminary investigation on the choice of density functional, basis set, and gauge indicates a similar dependence as for molecules: the functional is the primary factor that determines the OR magnitude, followed by the basis set and to a much smaller extent the choice of gauge. However, diffuse functions may be problematic for PBC calculations even if they are necessary for the molecular case. A comparison with experimental data of OR for the tartaric acid crystal shows reasonable agreement given the level of theory employed. The development presented in this paper offers the opportunity to simulate the OR of chiral crystalline materials with general-purpose DFT-PBC methods, which, in turn, may help to understand the role of intermolecular interactions on this sensitive electronic property.

Proximal Sensing of Density During Soil Compaction by Instrumented Roller

The measurement of density or void ratio during the compaction of geomaterials (soils and unbound granular materials) in the field during road construction is essential for superior performance. The specifications adopted by the road authorities worldwide are exclusively based on density. However, estimating density evolution proximally or non-destructively is challenging. Conventional field-based density measurement techniques are hazardous, slow to use and are point-based measurements. This study developed a novel methodology to estimate the density of geomaterials non-destructively in real-time during the compaction process. The methodology included measuring the surface deformation using Light Detection and Ranging (LiDAR) systems attached to rollers and developing physics-based 1-Dimensional and machine learning (ML) based constitutive models to relate the measured parameters to the density. The developed methodology was validated in an indoor environment where a large soil box (dimensions: 7.5 m×4 m×0.8 m) was fabricated and a well-graded sand in 5 layers of 100 mm was compacted using a 1.5-tonne instrumented roller. The measurement of deformation provided an opportunity to estimate the density in real-time. The estimated density using 1-D model and a ML based classification model had an error of 20% and 16% respectively when compared to density measured from Nuclear Density Gauge (NDG). This novel instrumentation allowed the density to be measured during compaction with high accuracy, which presents an unprecedented advantage over other conventional approaches, which are intrusive and pointwise, thereby ensuring that the road will be constructed expediently and will function satisfactorily, minimising the occurrence of premature failures. The continual measurement of density during compaction will also facilitate maintaining uniformity of the density, thereby reducing the potential for excessive differential deformations.

Incorporating New Technologies in Road Industry: Test Track in Antwerp, Belgium

Numerous factors may disrupt pavement construction including human errors and unforeseen changes in the environmental conditions. These incidents can shorten pavement life span. New technologies recently came to the aid of contractors and road agencies to detect and possibly mitigate undesirable impacts of unpredictable incidents during the asphalt paving process as well as monitoring pavement performance during pavements service life. In this study, several technologies including layer thickness assessment (using both MIT-scan device coupled with metal plates and conventional topographical technique), infrared thermal camera, intelligent roller compactors, and density gauge devices were utilized to develop a coherent construction system and improve the durability of asphalt pavements in Antwerp, Belgium. The data collected in situ were compared with the characterized cores in the laboratory. It was clear that several factors can influence the outcome of the employed devices. For instance, surface temperatures obtained from an infrared camera fluctuated when the camera tilted from the perpendicular axis. Such discrepancies may be associated with the changes in the distance and environmental condition that affect the refraction of the infrared spectra. It was also found that an elaborated data collection format is essential to clearly understand the correlations between the results of the employed technologies.

Sarcopenia does not predict outcome in patients with CNS lymphoma undergoing systemic therapy.

Low skeletal muscle mass as a proxy parameter for sarcopenia acts as a non-invasive imaging marker that is associated with poor prognosis in numerous types of cancer. The present study aimed to assess the influence of body composition parameters on overall survival (OS) and progression free survival (PFS) in patients diagnosed with primary central nervous system lymphoma (PCNSL). A total of 98 patients with PCNSL treated at University Hospital Magdeburg (Magdeburg, Germany) from 2013–2019 were retrospectively studied. Patients with a pre-treatment staging computed tomography (CT) scan that included the third lumbar vertebra were reviewed for analysis. Skeletal muscle area (SMA), skeletal muscle index (SMI), mean muscle density and skeletal muscle gauge (SMG) were measured on the CT scan prior to treatment. Parameters were associated with OS and PFS. Overall, 72 patients were included in the present study. Results of the present study demonstrated that the median OS was 10 months (range, 1–181 months), and 37 patients (51.4%) presented with sarcopenia. Moreover, the median OS was 7 months in the sarcopenic group and 32 months in the non-sarcopenic group. Results of the present study further illustrated that SMI, SMA, density and SMG did not exert a significant effect on OS. Notably, the median PFS was 2.5 months in the low SMI group and 10 months in the normal SMI group. Body composition parameters did not exert a significant effect on PFS. Overall, the results of the present study demonstrated that sarcopenia was not a risk factor for decreased OS or PFS in patients with PCNSL undergoing systemic treatment.

Quality is more important than quantity: pre-operative sarcopenia is associated with poor survival in advanced ovarian cancer

BackgroundSarcopenia is prevalent among older patients with cancer and is associated with poor outcomes.ObjectiveTo explore the relationship between muscle mass, quality, and patient age with overall survival after surgery for...

Development of a Density Gauge for Measuring Water and Mud Density based on a Radioactive Technique

The density or concentration of mud is one of the key variables in studying cohesive sediments, due to being accumulated through settlement and consolidation, as well as resuspended through erosion. This indicates that the proper measurement of sediment density is important. Therefore, this study aims to evaluate the accuracy of density measurement by using the gamma-ray attenuation method as a non-intrusive technique. For Compton Scattering, gamma-ray attenuation was effectively independent of mineralogy, subsequently depending on only the electron density of the material, which is directly related to the bulk density of the mixture. Based on the results, the advantages of utilizing the nucleonic density gauge indicated that the technique was non-intrusive and very flexible for many experimental arrangements, as well as the high accuracy of measurements with errors less than 1%.

Research on the Quality of Asphalt Pavement Construction Based on Nondestructive Testing Technology

In order to better evaluate the construction quality of asphalt pavement, nondestructive testing techniques are used to inspect newly paved asphalt mixture pavement. The proposed system for the evaluation of asphalt pavement construction quality uses three-dimensional ground-penetrating radar (GPR) and a non-nuclear density gauge. The GPR and the non-nuclear density gauge test results were used to establish a dielectric constant–porosity model by fitting. This approach can more accurately determine the dielectric constant selection scheme of the GPR based on the average value of every 10 dielectric constant data points in the length direction of the radar antenna and every three data channels in the width direction. The GPR collected the dielectric constants of the road surface based on the total reflection method and used the average value of the local dielectric constant to evaluate the construction quality of the road. The non-nuclear density gauge used the local porosity to assess the construction quality of the road. It is recommended that the two testing schemes described above be used to evaluate the quality of asphalt pavement construction. They can provide theoretical guidance for future applications in practical processes.

Use of Low-Activity Nuclear Density Gauge in Iron Oxide-Rich Soils

Nuclear density gauges (NDG) have been widely used for field compaction control. However, their shortcomings include the burden of licensing with nuclear regulatory agencies, gauge maintenance, storage and transportation restrictions, requirement to wear dosimeters, and radiation safety training. A recently developed low-activity NDG (LANDG) alternative utilizes a low-strength gamma ray source to measure soil density that is Nuclear Regulatory Commission exempt in the U.S.A. and its territories. An accompanying non-nuclear moisture probe yields the moisture content by measuring the dielectric constant of the soil. This study aims to compare the LANDG results with those of the NDG in two common soil types on the island of Oahu, Hawaii: volcanic soils and coralline soils. Coralline soils are partially broken down remains of coral comprised primarily of calcium carbonate. Volcanic soils are basalt derivatives rich in iron oxide and the question arises as to whether the iron oxide will affect the dielectric value resulting in erroneous moisture content measurements. This research shows that the LANDG and NDG measurements of total unit weight are in good agreement for both soils. The moisture content measurements from the LANDG’s accompanying moisture probe are in good agreement with those of the NDG in coralline soils but are less satisfactory in volcanic soils. A plausible explanation is offered. Moisture offsets may be applied to the moisture probe’s measurements to reduce scatter and increase accuracy. Instances of when this is required are suggested.

Correlation of ground penetrating radar and nuclear density gauge data to determine the density of asphalt pavement

This paper demonstrates the field performance of Ground Penetrating Radar (GPR) as a non-destructive testing tool to predict in situ asphalt pavement. In previous study, GPR has been used successfully in a variety of pavements application such as determining layer thickness, detecting subsurface distresses, and others. Nuclear Density Gauge (NDG) is specifically designed to measure the moisture and density of soils, aggregates, cement, and lime treated materials, and also to measure the density of asphalt concrete. Alternative analysis approaches by correlating the GPR and NDG data had been performed for density prediction of asphalt pavement. A density model name Al-Qadi, Lahouar, and Leng (ALL model) was used to predict the density of the asphalt pavement from the GPR data correlate with NDG database. This study shows that density for asphalt pavement from GPR data provide reasonably accurate density prediction when ALL model approach was used.