Density Gauge Research Articles

Real‐Time Evaluation of Compaction Quality by Using Artificial Neural Networks

The primary goal of this study is to find an easy and convenient way to estimate the degree of compaction in real time for compaction quality control. In this paper, an artificial neural network classifier is developed to identify the different characteristic patterns of drum vibration and classify them according to the different compaction levels. At first, a field compaction experiment is designed and performed in a construction site, and the degree of compaction and the vibration are measured. Then, the vibration signals collected from the experiment are processed to extract the features of vibration patterns and labeled with the compaction level to train the artificial neural network model. At last, the performance of the artificial neural network classifier is verified against the degree of compaction measured by using a nuclear density gauge. It can be found that artificial neural networks show good performance and huge potential for the problem of compaction quality control.

Assessment of Nuclear Moisture Density Gauges at a Secondary Standard Dosimetry Laboratory in Ghana during December 2015–December 2017

Introduction: Nuclear moisture density gauges are widely used in construction industry in different countries across the world, including Ghana, on a large scale. Like all irradiating devices, the nuclear gauges should be subjected to radiation safety assessment based on radiation protection and safety principles. Regarding this, the objective of this research was to investigate the radiation safety of the nuclear moisture density gauges to ensure the absence of any leakages from the radioactive source. Material and Methods: For the purpose of the study, a survey meter (RADOS-120) was used to measure and record the radiation dose once at a distance of 1 m from the surfaces of all sides of the nuclear moisture density gauge and very close distance from the surfaces of the device. Moreover, the device was examined using radiation contamination test and counts on a standard block. Results: A total of nine nuclear moisture density gauges manufactured by Troxler Electronics Inc. in the USA were evaluated within a period of 3 years. The minimum and maximum average dose rates were 0.49 and 66.67 μSv/h, respectively. The highest and lowest average dose rates were recorded in 2017 and 2016 on the devices with serial numbers of 38260 and 32839, respectively. Conclusion: The assessment of the nuclear moisture density gauges under study revealed noradiation contamination leakage. Furthermore, all the evaluated gauges were shown to function properly and were safe for the intended purposes.

Are primordial black holes produced by entropy perturbations in single field inflationary models?

We show that in single field inflationary models the super-horizon evolution of curvature perturbations on comoving slices ℛ, which can cause the production of primordial black holes (PBH), is not due to entropy perturbations, but to the background evolution effect on the conversion between entropy and curvature perturbations. We derive a general relation between the time derivative of comoving curvature perturbations and entropy perturbations, in terms of a conversion factor depending on the background evolution. Contrary to previous results derived in the uniform density gauge assuming the gradient term can be neglected on super-horizon scales, the relation is valid on any scale for any minimally coupled single scalar field model, also on sub-horizon scales where gradient terms are large. We apply it to the case of quasi-inflection inflation, showing that while entropy perturbations are decreasing, ℛ can grow on super-horizon scales, due to a large increase of the conversion factor. This happens in the time interval during which a sufficiently fast decrease of the equation of state w transforms into a growing mode what in slow-roll models would be a decaying mode. The same mechanism also explains the super-horizon evolution of ℛ in globally adiabatic systems, for which entropy perturbations vanish on any scale, such as ultra slow roll inflation and its generalizations.

Measuring the temperature dependence of water density by a designed gamma ray density gauge

Nowadays, nuclear instruments are being widely used in various scientific and industrial fields. Different types of nuclear radiations (alpha, beta, and gamma) can be used in the construction of these gauges. Gamma based densitometers, as non-contact and non-destructive test tools, are favorably being used for process monitoring in various industries, such as oil and petrochemical industries. Design and construction of a gamma ray density gauge and measurement of temperature dependence of water density via this gauge have been reported in this study. The results indicate that the designed device can measure the temperature dependence of water density with good accuracy.

In-Place Density of Asphalt Pavements: Case Study during Cold Weather Paving

Late-season paving is common and often performed in colder temperatures, which is the most challenging environment for attaining optimal in-place density and compaction. The in-place density of asphalt pavement greatly affects the life span of the pavement. This case study aims to evaluate and compare the effectiveness of different compaction, delivery, and mix design characteristics to ensure the optimization of in-place asphalt pavement density. To this end, four test sections were constructed over four separate days of paving during cold weather conditions. The in-place density was measured using four methods: (1) conventional or traditional cut roadway cores, (2) combination of infrared continuous thermal scanning (ICTS) with conventional or traditional cut roadway cores, (3) nonnuclear density gauge (NNDG), and (4) rolling density meter (RDM) utilizing ground-penetrating radar (GPR). The results revealed that during cold weather paving, the material transfer vehicles (MTVs) provide an effective method to minimize thermal segregation and therefore provide improved temperature and density consistency. In addition, the combination roller provided a consistent improvement compared to the standard three double-drum steel roller compaction method. It was shown that ICTS is an effective measuring technique, especially for paving in cold weather conditions, since it provides real-time information to the producer for improving temperature consistency that will result in more uniform densities. The use of nondestructive testing equipment can also strengthen the acceptance procedure in a more rigorous way by increasing the testing frequency.

Practical method for in-place density measurement of cold in-place recycling mixtures

Cold in-place recycling (CIR) has been used for the past two decades as an effective rehabilitation technique for deteriorated asphalt concrete (AC) pavements. The CIR process consists of milling the top portion of the deteriorated AC layer, mix the reclaimed asphalt pavement (RAP) with asphalt emulsion and additive such as lime or portland cement, and compact. The generated CIR layer serves as a good base under the new AC overlay. The most critical property of the CIR layer is its excellent resistance to reflective cracking which makes it a highly effective rehabilitation treatment for cracked AC pavements. Other rehabilitation alternatives such as straight AC overlay would suffer from reflective cracking at the rate of 25 mm per service year.There are five parts of the CIR process; 1) milling, 2) mixing, 3) laydown, 4) compaction, and 5) overlay. Parts 1, 2, 3, and 5 have been well established while part 4 is still requires major improvements. Up to this date, the measurement of the in-place density of the compacted CIR layer is un-achievable. In the case of the AC layer, the in-place density during compaction is measured through a nuclear density gauge that has been calibrated against cores cut from the compacted mat. The application of the same process for the CIR layer faces major limitations: a) in-ability of the nuclear gauge to measure density due to excess water and b) cores cannot be cut from the CIR mat until the 14 days curing has occurred. This paper describes a new method to measure the in-place density of the CIR layer during the compaction process. The new method uses the Sand Cone apparatus to measure the bulk density of the compacted CIR layer. The proposed method has been validated through laboratory testing and field evaluation.

Field Assessment of Non-nuclear Methods Used for Hot Mix Asphalt Density Measurement

Destructive nature along with the associated higher cost of the traditional core method used for hot mix asphalt density measurement has convinced researchers switching to some non-destructive technique for this purpose which is cost efficient as well. Earlier, nuclear density gauges were introduced for this purpose which was non-destructive as well. Since such devices were associated with the use of gamma rays, therefore, leading to safety and health issues. Last decade observed a revolution in asphalt density measurement technique with the evolution of non-nuclear density gauges. This research work is carried out with the objective to determine the efficiency and accuracy of a newly developed non-nuclear density gauge i.e. PQI-380 for field conditions as it needs its thorough evaluation prior to future uses in many of the developing countries including Pakistan. Density data obtained using standard core method and non-nuclear density gauge for 195 location confirms the satisfactory performance of the instrument. Results obtained show that the coefficient of correlation is near to 0.9. which refers to a strong correlation between the density data. Moreover, performance criteria e.g. root mean square error and mean absolute error between the density data set is also very low confirming the good measuring abilities of the device. Instrument performed well for repeatability analysis giving maximum coefficient of variance less than 5 percent.

Second-order cosmological perturbations: New conserved quantities and the general solution at super-horizon scale

The study of long wavelength scalar perturbations, in particular the existence of conserved quantities when the perturbations are adiabatic, plays an important role in e.g. inflationary cosmology. In this paper we present some new conserved quantities at second order and relate them to the curvature perturbation in the uniform density gauge, $\zeta$, and the comoving curvature perturbation, ${\cal R}$. We also, for the first time, derive the general solution of the perturbed Einstein equations at second order, which thereby contains both growing and decaying modes, for adiabatic long wavelength perturbations for a stress-energy tensor with zero anisotropic stresses and zero heat flux. The derivation uses the total matter gauge, but results are subsequently translated to the uniform curvature and Poisson (longitudinal, zero shear) gauges.

Evaluation of a non-nuclear density gauge as an alternate to destructive coring for airport asphalt acceptance testing

A non-nuclear density gauge (NNDG) was evaluated as part of an asphalt runway resurfacing project. The repeatability of the NNDG was found to be high but asphalt temperature and surface moisture had a significant effect on the reliability of NNDG inferred asphalt density. It was also found that a single NNDG inferred density, located immediately over the core location, provided greater agreement with core density than an averaged NNDG density over and around the location of the core. It was concluded that when used 1 day behind the surface paving operation, when the temperature had stabilised and the surface was dry, the NNDG was a reliable replacement for destructive coring for density measurement. Consequently, the coring frequency was reduced by 75% following NNDG calibration. However, the influence of temperature and moisture rendered the NNDG less suited to quality control during the compaction rolling process. Finally, it is recommended that additional research be undertaken to extend these conclusions to other asphalt mixtures, allowing other airports to reduce the frequency of destructive coring for density testing during asphalt resurfacing, following mixture-specific calibration of the NNDG.

Investigation of room temperature ferromagnetism in transition metal doped BiFeO3

Spintronic functionality in ferromagnetic materials is a next-generation technique, to be used in data storage, high-frequency communications, and logic devices with minimum energy consumption. Ultra-low energy consumption in high-speed logic devices can be envisioned by inducing ferromagnetic behavior into room temperature multiferroic materials. However, there is a scarcity of room temperature multiferroic materials which have a definite spin degree of freedom. To fully exploit these technological challenges, we introduce the induced ferromagnetism in bismuth ferrite (BiFeO3, BFO) by doping transition metal (Cr, Ni, Co) elements. Our investigation initiates with the experimental study on chemically synthesized BiFe(1−x)MxO3 samples where x = 0.0625 (6.25%) and M = Cr, Ni and Co. Experimental findings are verified by theoretical simulation using density functional theory (DFT + U) and gauge including projector augmented wave (GIPAW) based calculation. All the experimental studies are done at room temperature while the theoretical verification using DFT is carried to understand the underlying mechanism behind the magnetic behavior of doped BiFeO3. It is done by optimizing the structural parameters comparable to the room temperature values. Microstructural and magnetic properties are studied using x-ray diffraction (XRD), transmission electron microscopy (TEM) and Vibrating sample magnetometer (VSM). All these experimental studies confirm the structural changes and induced ferromagnetism with doping. X-ray photoelectron spectroscopy (XPS) verified the reason behind this ferromagnetic property on the basis of oxygen vacancy content. Electron paramagnetic resonance (EPR) spectroscopy shows the tuning of Δg values due to enhanced magnetization.The density of states (DOS) calculations were performed on BFO (band-gap 1.89 eV) after structural optimization using DFT + U method, confirm our experimental findings. Magnetic moment values change drastically with doping elements (M), i.e. almost negligible for BFO (antiferromagnetic) to maximum (2.85 μB/f.u.) for Ni-doped sample. We also compute the EPR g-tensor using GIPAW method to confirm the tuning of Δg values due to enhanced magnetization. These results can highlight the impact and importance of suitable transition element doping to induce the room temperature ferromagnetism in BiFeO3.

The Applicability of Soil Density Gauge in The Detection of Non-Cohesive Soil

With the needs of engineering construction, non-cohesive soil has been widely used in important fields such as dams and roadbed filling. The strength and compressibility of non-cohesive soil mainly depend on the compactness.However, it has so far been difficult to find a method for determining the compactness of non-cohesive soil quickly, accurately and safely.In order to cope with this problem, this paper focuses on the working principle and operation process of the SDG200 soil densitometer.At the same time, on the basis of summarizing the previous research, it is pointed out that the difference between the operation of clay soil and non-cohesive soil density is tested by SDG soil densitometer, and the parameter setting problem in the non-cohesive soil compactness test is solved.Therefore, it can be predicted that the SDG soil densitometer will have a good application prospect in the detection of non-cohesive soil compactness.

Nuclear density gauge compaction testing alternatives: synthesis and critical analysis

ABSTRACTThe costs of training, licensing and security for agencies using the nuclear density gauge (NDG) have become increasingly onerous for public engineering agencies, leading them to seek less expensive alternatives to conduct compaction testing. The study focused on three comparators: difference in approaches between tested devices and methods, the setting of targets for modulus stiffness devices and the examination of reported accuracy and reliability. This paper’s objective is to summarize the reported results for each alternative and provide the details of the findings. The paper finds that previous research has been almost exclusively focused on laboratory testing and is nearly devoid of authoritative information on field test performance parameters such as repeatability and time to complete a field test. It concludes that research is needed that includes a broad set of testing methods and equipment on the same set of soil conditions. The paper’s primary contribution is to consolidate and critically analyze the results of the current compaction testing research and benchmark the state-of-the-practice in field compaction testing. This paper does provide comparisons without intent to identify a “best” alternative because each device is adapted to specific soil conditions. Testing agencies may require differing devices based on budget, manpower and training.

Indirect density tests for thin asphalt overlay – part 1: review

Quality in construction of asphalt pavements plays a significant role in long-term durability. In situ density is a key parameter in construction quality and there are several available test methods. However, there are questions as to whether a particular test provides density values (referred to as ‘quality assurance’) or density changes (referred to as ‘quality control’). This paper presents findings from a literature review of indirect density testing on asphalt pavements. A specific interest is on thin overlays in the 30–50 mm thickness range typically used in the UK. Indirect test methods include nuclear density gauge, electromagnetic instruments, ground-penetrating radar and step frequency radar. The advantages and limitations of these methods for thin asphalt in situ density measurement are discussed in this paper.

Evaluation of three nondestructive testing techniques for quality assessment of asphalt pavements

ABSTRACTThis study evaluates three nondestructive testing (NDT) techniques for quality assessment of asphalt pavements. The three NDT techniques examined include an electromagnetic density gauge, a dynamic stiffness gauge, and geophysical surface wave tests for measuring modulus. In-situ NDT tests were carried out for four representative paving projects covering a range of asphalt mixes and traffic loads, and cores were extracted at the centre of each NDT testing location for laboratory measurement of density and modulus. A comprehensive correlation analysis was carried out to examine the performance of each NDT method for quantifying the quality of the asphalt pavements. The in-situ density had a low correlation with the laboratory density and was not sensitive to variations in temperature and asphalt mix type. The in-situ stiffness measured on the asphalt mixtures several hours after paving had a high correlation with the in-situ dynamic modulus and laboratory density, and is therefore recommended as a quantitative property for quality control. Among the three NDT measurements, the in-situ modulus was most sensitive to variations in temperature and asphalt mix type. After correction for temperature effects, the corrected modulus is recommended as a quantitative property for quality assurance.

Evaluating the Potential for Replacing the Nuclear Density Gauge using Nonnuclear Alternative Devices and Methods

Abstract This study was initiated with the aim of replacing the nuclear density gauge (NDG) with nonnuclear alternative methods that can be used as acceptance tools during the compaction of soils and dense graded aggregates (i.e., unbound pavement layers). To fulfill this objective, a laboratory procedure for compacting large samples was developed. This procedure facilitated testing using three nonnuclear devices: Briaud compaction device (BCD), light weight falling deflectometer (LWD), and dynamic cone penetrometer (DCP). Four types of aggregates, two subgrade soils, one dense graded aggregate, and one recycled concrete aggregates, were selected to comprehensively cover a wide range of subgrade and base/subbase materials typically used in the State of New Jersey (NJ). Each device was evaluated for accuracy and repeatability. The sensitivity of the results measured from each device to moisture content, compaction effort applied, and testing time was also evaluated. Based on testing results, it was found that the DCP was most sensitive to detecting changes in the measured parameters. The results also indicated that the DCP was the most suitable device for replacing the NDG.

Comparative analysis of repeatability and reproducibility of compaction testing

This article investigates alternatives for soil compaction testing to potentially replace the standard nuclear density gauge by examining alternate testing devices and methods. Gauge reproducibility and repeatability is used to compare various devices including the Light Weight Deflectometer and the Dynamic Cone Penetrometer. The objective of this study is to find the appropriate means for measuring repeatability and reproducibility in the field for the testing devices. This article considers both measurement system analysis in the form of gauge repeatability and reproducibility and statistical data assessments including: (1) coefficient of variation; (2) statistical error compared to the mean; (3) one-way ANOVA; and (4) hypothesis test for paired samples.

Investigation of rotameric conformations of substituted imidazo-[1,2-a]pyrazine: experimental and theoretical approaches.

The different rotameric conformations of imidazo-[1,2-a]pyrazine have been synthesized and characterized by means of different experimental techniques, such as NMR, FTIR, and absorption spectroscopy and quantum chemical calculations. The different conformations were stabilized by hydrogen bonds, such as OH⋯N, ArH⋯N and ArH⋯ArH. The ground state optimizations and potential energy surface (PES) scanning profiles produced using density functional theory (DFT) show two stable rotameric forms for each molecule. The relative population of the conformations is affected by the strength of the hydrogen bonds. The calculated absorption spectra and isotopic shielding constants were acquired by time-dependent density functional theory (TD-DFT) and gauge invariant atomic orbitals (GIAO)-DFT, respectively. The strength of the hydrogen bonding interactions that resulted in the different conformations was studied by quantum theory of atoms in molecules (QTAIM).

Nuclear gauge application in road industry

Soil compaction is essential in road construction. The evaluation of the degree of compaction relies on the knowledge of density and moisture of the compacted layers is very important to the performance of the pavement structure. Among the various tests used for making these determinations, the sand replacement density test and the moisture content determination by oven drying are perhaps the most widely used. However, these methods are not only time consuming and need wearisome procedures to obtain the results but also destructive and the number of measurements that can be taken at any time is limited. The test can on be fed back to the construction site the next day. To solve these problems, a nuclear technique has been introduced as a quicker and easier way of measuring the density and moisture of construction materials. Nuclear moisture density gauges have been used for many years in pavement construction as a method of non-destructive density testing The technique which can determine both wet density and moisture content offers an in situ method for construction control at the work site. The simplicity, the speed, and non-destructive nature offer a great advantage for quality control. This paper provides an overview of nuclear gauge application in road construction and presents a case study of monitoring compaction status of in Sedenak - Skudai, Johor rehabilitation projects.

Estimating Carbon and Nitrogen Pools in a Forest Soil: Influence of Soil Bulk Density Methods and Rock Content

Core Ideas Three bulk density methods used in a rocky soil gave different total bulk density values, but not fine bulk density. Bulk density sampling method had little effect on C and N pool estimates in the surface 20 cm of soil, but did so deeper in the soil. Small‐diameter cores probably underestimated total soil bulk density and C and N pools at deeper soil depths. Rocks present on the soil surface cause an overestimation of soil C and N pools. Soils with high rock content are common in many US forests, and contain large amounts of stored C. Accurate measurements of soil bulk density and rock content are critical for calculating and assessing changes in both C and nutrient pool size, but bulk density sampling methods have limitations and sources of variability. Therefore, we evaluated the use of small‐diameter soil cores (SD), irregular soil volume excavation (IR), and a nuclear density gauge (ND) to measure bulk density and rock content, and estimate C and N pools in three 10‐cm increments to a 30‐cm depth in a glacial till soil in northern Wisconsin. Total and fine bulk densities were lower when measured with SD cores than with larger soil volume IR and ND methods. No differences in C pools among bulk density sampling methods were found in the 10‐cm increments, but when combined to 30 cm, the C pool estimate with IR (81.6 Mg ha–1) was significantly higher than those of ND (75.3 Mg ha–1) and SD (73.4 Mg ha–1). No significant differences in N pools were detected in the 10‐cm increments, but the 0‐ to 30‐cm N pool estimates by IR (5.65 Mg ha–1) and ND (5 Mg ha–1) were higher than that of SD (4.22 Mg ha–1). Surface rocks could lower soil C and N pools by 20% or more. Overall, the bulk density method had little effect on soil C and N pool estimates in the surface 20 cm of this soil but did when sampled to 30 cm soil depth.

Laboratory evaluation of electromagnetic density gauges for hot-mix asphalt mixture density measurement

This paper presents a laboratory study aiming to evaluate the performance of electromagnetic (EM) density gauges as a non-destructive tool for hot mix asphalt (HMA) density measurement. In total, 36HMA testing slabs with different compositions were prepared in laboratory. EM density gauge data were collected from these slabs using two common types of gauges, i.e., PQI 301 and PaveTracker 2701B, and compared with their bulk densities measured by the standard saturated surface dry (SSD) method. It was found that measurement direction, asphalt binder content, mixture air void content, and thickness of the testing slabs do not affect the accuracy of the EM density gauges. However, EM density gauge measurements are affected by the presence of moisture, gradation of asphalt mixture and gauge calibration method. It was also concluded that the accuracy of PaveTracker with mix calibration is comparable to that of the conventional standard method.