Density Gauge Research Articles

Research on the Method of Non-Uniformity Control in Asphalt Pavement Construction with PQI

Non-uniformity of the asphalt pavement is one of most important reason for early disease, control of non-uniformity in the production process of asphalt pavement is an important measure to ensure that quality and service life of pavement. Nuclear density gauge (PQI) can be non-destructive, rapid detection of asphalt pavement density. This paper give a research and application on the PQI calibration, testing frequency, the control parameters and evaluation index, and proposes a control method of non-uniformity in asphalt pavement construction with PQI. Asphalt pavement quality control in construction process can use this method. It is important to improve the stability of asphalt pavement quality and reduce the incidence of disease, and also has a certain reference value for establishing the quality control and quality assurance systems.

A single scatter electron Monte Carlo approach for simulating gamma-ray stopping efficiencies of Geiger-Müller counters

Abstract In spite of their relatively poor gamma-ray stopping efficiencies, the Geiger-Muller (GM) counter is still preferred in many radioisotope gauges for industrial measurements. This is because these detectors exhibit a high degree of robustness in harsh environments, are relatively insensitive to temperature changes in the environment, and are inexpensive compared to other types of radiation detectors. These properties could make the use of GM counters very feasible in a number of industrial applications, such as gamma-ray tomography and gamma-ray density gauges, provided that their gamma-ray stopping efficiencies can be improved. The Monte Carlo (MC) method is a powerful computational physics tool that is utilized very often in the design of radiation detectors and radioisotope gauges. In this work a MC model for GM counters that is benchmarked with experiments at the primary photon energy of 59.5 keV is proposed. This is a specific purpose MC simulation code that, as opposed to publicly available general purpose MC codes, employs single scatter (or microscopic) electron transport and is currently under development. In this paper, the MC code is described in detail and the results of the specific purpose MC code are benchmarked with experiments and two general purpose MC codes, MCNP5 and PENELOPE. It was observed that the specific purpose MC code improved the reduced chi-square value when compared to MCNP5 and PENELOPE.

Structural Response of Pervious Concrete Pavement Systems Using Falling Weight Deflectometer Testing and Analysis

Although pervious concrete material properties, mix design, and storm water applications are well documented in the literature, the structural behavior of pervious concrete pavement systems has not been investigated. A parking lot was constructed in which traditional impervious concrete was used on half of the parking lot and pervious concrete was used on the other half. The traditional concrete layer was placed on natural subgrade. The pervious concrete portion was divided into two sections with two pervious concrete mixtures and aggregate base thicknesses of 300 and 450 mm. To better understand the behavior of traditional and pervious concrete pavement systems of the parking lot, the subgrade soil properties were characterized by using plate load testing and nuclear density gauge. Furthermore, the aggregate base layers used in the pervious concrete systems were characterized by using plate load testing. After constructing the parking lot, falling weight deflectometer (FWD) testing was performed on the t...

A Study for Implementation of Density Measurement Equipment for Asphalt Pavement based on the electromagnetic capacitance

In this paper we developed density measurement equipment for Asphalt Pavement based on the electromagnetic capacitance. This kind of Non-Nuclear Density Gauges technology and products is used or studied in USA, Finland, Sweden as standardization of authorized method for pavement density measurement. Effective permitivity of pavement asphalt is characterized in electromagnetic capacitance by the asphalt material, mixed ratio, and harden grade of pavement asphalt. We can get a density value of asphalt by replacing value of electromagnetic capacitance with standard density value and characteristic transformation curve. We are conformed that measurement data according to temperature, humidity, and real field asphalt of our density measurement equipment can be a precise value.

High Field 33S Solid State NMR and First-Principles Calculations in Potassium Sulfates

A set of potassium sulfates presenting a variety of sulfur environments (K(2)SO(4), KHSO(4), K(2)S(2)O(7), and K(2)S(2)O(8)) has been studied by (33)S solid state NMR at 21 T. Low natural abundance (0.75%) and small gyromagnetic ratio of (33)S presented a serious challenge even at such a high magnetic field. Nevertheless, using the QCPMG technique we were able to obtain good signals from the sites with C(Q) values approaching 16 MHz. Assignment of the sites and the relative orientations of the EFG tensors were assisted by quantum mechanical calculations using the Gaussian 98 and CASTEP packages. The Gaussian 98 calculations were performed using the density functional method and gauge independent atomic orbitals on molecular clusters of about 100-120 atoms. The CASTEP calculations utilized periodic boundary conditions and a gauge-including projector augmented-wave pseudopotential approach. Although only semiquantitative agreement is observed between the experimental and calculated parameters, the calculations are a very useful aid in the interpretation of experimental data.

Factors Affecting Variance and Bias of Non-Nuclear Density Gauges for Porous European Mixes and Densegraded Friction Courses

It is well known that the implementation of contractor quality control/agency quality assurance (QC/QA) can support quality improvements in hot mix asphalt (HMA) pavements, both for porous European mixes (PEMs) and dense-graded friction courses (DGFCs). On the other hand, many reasons and reports highlight the importance of proper in situ air voids content, due to major influence on service properties (rate of rutting, fatigue life, structural strength, permeability, ravelling, etc.). Another relevant standpoint is that in-lab determinations of density, though often reliable and accurate, are low-speed tests. All these facts outline the potential role of field measurement of density through non-nuclear density gauges. In the light of the above facts, the main object of the paper was confined as the study of factors affecting variance and bias of non-nuclear density gauges both for PEMs and DGFCs. Bias, variance and parameters’ dependence resulted to be appreciably affected by mix typology and characteristics. In particular, when related to mix type, monovariate regressions with low-speed methods resulted able to provide a useful tool in QC/QA procedures and road asset management. Further practical applications have been outlined.

Calibration of Non-Nuclear PQI Gauges and Field Comparison of PQI and Nuclear Gauge Densities

Traditionally, a nuclear density gauge is used as a quality control (QC) and quality assurance (QA) tool for in-place density of asphalt pavements. The nuclear-based devices, however, tend to have problems associated with licensing, equipment handling, and storage. The Pavement Quality Indicator (PQI), manufactured by TransTech Systems, Inc., is a non-nuclear device that determines the density of an asphalt pavement layer based on the principle of electrical impedance and the dielectric constants of associated materials. To this end, field data was generated from six field projects for calibration of a PQI 301 gauge. The performance of the PQI gauge was compared with a nuclear density gauge in four field projects and was validated against laboratory densities (AASHTO T 166) measured from selected cores extracted from the pavements. It was observed that 5-point data instead of 13-point data can be used for PQI density with 95% certainty in all the cases. PQI densities exhibited better correlation with AASHTO T 166 densities when the PQI was used before the pneumatic roller. A PQI gauge calibrated with 5 cores exhibited similar performances as the PQI gauge calibrated with 10 cores. It was noticeable that PQI 301 produced better coefficient of determination than the nuclear gauge when the PQI gauge was used before the pneumatic roller. Finally, both mean squared error as well as R-squared values should be used for calibration purposes.

The non-adiabatic pressure in general scalar field systems

We discuss the non-adiabatic or entropy perturbation, which controls the evolution of the curvature perturbation in the uniform density gauge, for a scalar field system minimally coupled to gravity with non-canonical action. We highlight the differences between the sound and the phase speed in these systems, and show that the non-adiabatic pressure perturbation vanishes in the single field case, resulting in the conservation of the curvature perturbation on large scales.

Design, optimization and calibration of an automated density gauge for firn and ice cores

AbstractA gamma-ray density gauge can provide high-resolution and high-precision density measurements of firn and ice cores. This study describes the design, gamma-ray energy optimization and mass attenuation coefficient calibration of the Maine Automated Density Gauge Experiment (MADGE), a portable, field-operable gamma-ray density gauge used on overland traverses in East Antarctica. The MADGE instrument uses a 241Am gamma-ray source, a pulse-mode counting system and electronic core diameter calipers to collect high-precision (±0.004 g cm−3) density data from 3–8 cm diameter firn and ice cores. The data are collected at a 3.3 mm spatial resolution and an average throughput of 1.5 m h−1 for 5 cm diameter cores.

The application of radiation sources in the oil and gas industry and shortages in their services

Oil and gas industries utilise many radiation sources in various applied radiation-based technologies. Those technologies provide significant benefit to the daily operations of the industry. Gamma emitting sources of Cs-137, Co-60, Ba-133, Am-241 are used in oil and gas well logging, in Multiphase Flow Meter (MPFM) technology at oil and gas production facilities and in transmitted level gauges for tanks in refineries. X-ray Fluorescence (XRF) is used for sulphur gauges in laboratories. Cd-109 and Fe-59 are used in alloy analysers in refineries and workshops. Neutron sources like Cf-252 or 241Am-Be are used in density gauges and also in well logging. Ir-192 and Co-60 are routinely used in industrial radiography. Bi-113 and X-ray machines are used routinely in industrial security. To maximise benefits and minimise hazards associated with utilisation of radiation-based technologies, national radiation protection standards are implemented. The use of radiation sources needs regular services. There are shortages in the application of the needed radiation sources' services within the Kingdom of Saudi Arabia. This paper will provide samples of radiation-based technologies used in the oil and gas industry and pay particular attention to few shortages in the radiation services needed for the safe handling of the sources that need to be rectified in order to encourage and assist the new radiation sources' users to utilise radiation-based technologies in the industry.

Investigation of the Nuclear Gauge Density Calibration Method

ABSTRACT Nuclear gauges have been used in the compaction control of pavement construction since 1950s. The accuracy of nuclear testing significantly relies on the calibration of nuclear gauges, which establishes the correlation between material density and nuclear gauge count reading in the form of a calibration equation with several constants. The choice of a calibration equation not only changes with engineering conditions and requirements, but also depends on the physical principals of measurement. This paper investigates several forms of calibration equations. Numerical analysis is conducted to show the capabilities of different calibration equations using the existing experimental results. Although the exponential equation with three constants is favourable due to its physical soundness, it does not consistently provide the best agreement with experiments. To reach a higher accuracy, a modified four-standard-block calibration method is proposed. The advantage of this method is demonstrated with the experimental data.

Crushed Glass-Dredged Material (CG-DM) Blends: Role of Organic Matter Content and DM Variability on Field Compaction

Trial embankments comprised of crushed glass-dredged material (CG-DM) blends and a 100% DM embankment were constructed to provide the necessary data sets to determine if a moisture content (MC) correction was required for the nuclear density (ND) gauge, as DM may contain a high organic matter content (OC). The MCs of thin-walled tube samples of CG-DM blends collected immediately below the ND gauge were compared to the corresponding ND gauge readings. A direct correlation between the MC data pairings from the tube samples and ND gauge readings showed that the ND gauge was greater than 97% accurate for MCs up to 55% and OCs up to 10% for the CG-DM blends evaluated in this study. However, the MC determined by the ND gauge was underpredicted (not overpredicted) by approximately 2.5%, contrary to theoretical expectations. A comparison of the average MC results per embankment indicated that the ND gauge was generally within 1% of the tube sample values, again on the low side. Interestingly, the rutting of the individual embankment lifts, often used as an informal metric for compaction compliance also was found to be contrary to expectations. The (re)constructed CG-DM embankments of this study were again shown to satisfy local Department of Transportation embankment construction criteria in most cases.

Baseline Radioactivity Measurements In The Vicinity Of A Gold Processing Plant

Studies were conducted in the vicinity of a gold processing plant at Tarkwa (Western Region, Ghana) to obtain baseline radioactivity data prior to the installation of Cs-137 nuclear density gauges for quality control measure-ment of the density of slurry in the pipelines at the plant. A survey meter, gamma spectrometry and alpha-guard were used to obtain data on radionuclide concentrations in the environment, and determine the effective dose to workers. The results indicated the absence of any artificial radioactivity within the environs of the plant. The levels of Cs-137 before installing the gauges were within the detection limit of 1.5 Bq/kg. The effective doses estimated from the naturally occurring radionuclides were within the limits set by International Commission on Radiological Protection. Journal of Applied Science and Technology Vol. 12 (1&2) 2007: pp. 18-24

On the use of prompt gamma-ray neutron activation analysis for determining phase amounts in multiphase flow

Prompt gamma-ray neutron activation analysis (PGNAA) is considered for the measurement of the in situ multiphase flow amounts of oil, gas, water and salt in a deep sea oil well. PGNAA has the advantages for this application that: (1) useful characteristic prompt gamma rays are produced by neutron interactions with almost all elements, (2) it is a rapid non-destructive measurement method, (3) a large sample volume is measured and (4) it can be used under the relatively extreme conditions present for undersea oil recovery. Feasibility calculations have been made with the previously developed Monte Carlo–library least-squares (MCLLS) measurement approach used with the specific purpose Monte Carlo code named CEARCPG that was previously developed at CEAR for PGNAA bulk material analysis. A slight modification of the MCLLS measurement approach previously developed for the nonlinear PGNAA and energy dispersive x-ray analysis (EDXRF) measurement applications is used for the present application. This modification allows the use of the very accurate forward Monte Carlo calculation of the PGNAA response and consists of using first the three components oil plus gas, water and salt as library spectra rather than the normal use of individual elemental libraries. Then the gamma-ray transmission density gauge response from the Cs-137 source is used to obtain the amount of gas. This approach allows one to determine the four parameters of primary interest directly. The arrangement considered is the use of a Cf-252 neutron source and a Cs-137 gamma-ray source with a large NaI detector placed on the opposite side of a right circular cylindrical sample holder for an assumed homogeneous mixture of oil, gas and seawater. A background that was previously obtained experimentally in bulk analysis applications was added in various amounts to the response here to make the calculations more reasonable. More experimental results for benchmarking will be taken in the future. Results indicate that this approach would be accurate and is feasible.

Density perturbations inf(R)gravity theories in metric and Palatini formalisms

We make a detailed study of matter density perturbations in both metric and Palatini formalisms. Considering general theories whose Lagrangian density is a general function, $f(R)$, of the Ricci scalar $R$, we derive the equation of matter density perturbations in each case, in a number of gauges, including comoving, longitudinal and uniform density gauges. We show that for viable $f(R)$ models that satisfy cosmological and local gravity constraints (LGC), matter perturbation equations derived under a subhorizon approximation are valid even for super-Hubble scales provided the oscillating mode (scalaron) does not dominate over the matter-induced mode. Such approximate equations are especially reliable in the Palatini formalism because of the absence of scalarons. Using these equations we make a comparative study of the behavior of matter density perturbations as well as gravitational potentials for a number of classes of $f(R)$ theories. In the metric formalism the quantity $m=R{f}_{,RR}/{f}_{,R}$ that characterizes the deviation from the $\ensuremath{\Lambda}\mathrm{CDM}$ model is constrained to be very small during a matter era in order to ensure compatibility with LGC, but the models in which $m$ grows to the order of ${10}^{\ensuremath{-}1}$ around the present epoch can be allowed. These models also suffer from an additional fine-tuning due to the presence of scalaron oscillating modes which are absent in the Palatini case. In Palatini formalism LGC and background cosmological constraints provide only weak bounds on $|m|$ by constraining it to be smaller than $\ensuremath{\sim}0.1$. This is in contrast to matter density perturbations which, on galactic scales, place far more stringent constraints on the present deviation parameter $m$ of the order of $|m|\ensuremath{\lesssim}{10}^{\ensuremath{-}5}--{10}^{\ensuremath{-}4}$. This is due to the peculiar evolution of matter perturbations in the Palatini case, which exhibits a rapid growth or a damped oscillation depending on the sign of $m$.

Comparison of Nuclear and Nonnuclear Pavement Density Testing Devices

The density of a hot-mix asphalt (HMA) pavement is an important factor for assessing pavement quality. Sufficient density is an essential characteristic of a well-constructed pavement and will lower its potential for distress. Traditionally, pavement density is determined by laboratory measurements of core samples and in situ readings via nuclear density gauges. Recently, nonnuclear devices that measure the electromagnetic properties of pavements have been developed. Nonnuclear devices have an inherent advantage over nuclear density gauges in that stringent monitoring of the user and extra security precautions are not required. However, the literature is unclear whether the readings from these devices are equivalent to those from nuclear density gauges. In this study, in-place pavement density readings from nonnuclear and nuclear density gauges were compared with laboratory-measured density values from core samples taken from the same location. Density readings from both gauges were compared with density measurements from the core samples for percent difference, correlation analysis, and hypothesis testing. However, the effect of moisture in the HMA was found to have a significant impact on density readings from the nonnuclear gauge. For seven of eight projects when a regression-based correction incorporating the qualitative moisture index was applied to the nonnuclear gauge density readings, the densities were better correlated to core density measurements than were densities from a traditionally used nuclear density gauge. On the basis of this study, the nonnuclear density gauge is more suitable than the nuclear density gauge for measuring pavement density on dense-graded HMA, provided that the readings are corrected using the qualitative moisture index.

Parameter Estimation for Evaluation of in Situ Density and Moisture Content by using Elastic and Electromagnetic Wave Propagation

Soil density and moisture content are two essential properties in the quality control and quality assurance of projects that involve soil compaction. However, current field practices either are destructive and time-consuming (i.e., sand cone or water balloon for soil density and oven drying for moisture content) or include hazardous substances that require special handling and operating procedures (i.e., nuclear density gauge). Therefore, new robust, reliable, and nonnuclear techniques for the determination of in situ density and moisture content would assist in quality control and quality assurance processes and would allow more measurements to be performed in a shorter time. A methodology for the in situ determination of density and moisture content by using the propagation of elastic and electromagnetic waves through soils was evaluated. It is based on a semiempirical model that relates elastic wave velocity through soils to the water content, porosity, and degree of saturation. An experimental program was used to verify the model and examine its range of applicability. It was also used to examine the accuracy and limitations of the suggested methodology. An analysis was made of the experimental assessment, along with a detailed numerical study of the inversion procedure used to calculate the density and moisture content. Although the parametric and experimental study shows that the methodology can provide an estimate of density and water content rapidly and non-destructively, there are inherent accuracy and precision limitations that need to be solved. These results also show that combined elastic and electromagnetic wave propagation measurements can help in the development of a methodology that may assist in solving inconsistencies in stiffness measurements.

Comparison of gage and multi-sensor precipitation estimates over a range of spatial and temporal scales in the Midwestern United States

An intercomparison of radar-estimated precipitation and gage precipitation at a monthly time scale with a county spatial resolution was undertaken for a nine-state region of the Midwestern United States. Daily gage and radar-estimated precipitation data also were examined at the county and grid cell scale for several smaller regions. Precipitation data were collected from February 2002 to August 2005 from three sources: (1) gridded radar (stage II, RDR) and multi-sensor precipitation estimates (MPE) based on the stage III/IV algorithm developed by the Office of hydrology/NWS River Forecast Centers, (2) quality-controlled National Weather Service (NWS) cooperative gage (QC_Coop) data from the National Climatic Data Center (NCDC), and (3) gage data from three high density networks in Illinois. Both the QC_Coop and high density gage data were employed as the reference standard. Sixty-four percent of QC_Coop versus MPE county-averaged monthly precipitation estimates agreed to within ±25%, with a median difference of 5.6% (QC_Coop greater than MPE) for the Midwest region. The difference between gage and MPE monthly values decreased somewhat through the 41-month period of study, and the correlation between monthly estimates increased, averaging 0.80. Data from three regional gage networks indicated that on a daily basis, network-averaged MPE and gage data also agreed to within about ±25%, and the MPE values tended to be lower than gage amounts at higher precipitation values. When examining multiple gages within single MPE grid cells, it was found that the number of gages employed in computing the gage average did not appreciably affect the correspondence between MPE and gage precipitation amounts. This also was found examining monthly values at the county level. For daily precipitation at the grid cell scale, for daily networked-averaged precipitation for each of the regional networks, and for monthly county-averaged precipitation values across the Midwest, MPE values are often larger than gage values for lower gage precipitation totals, and as precipitation totals increase, MPE values are more likely to be the same or smaller than the gage value.

Field and Lab Investigations of Prematurely Cracking Pavements

A forensic study was conducted to identify the cause of the premature cracking on three recently completed projects that were built with the same design. Nondestructive [ground penetration radar, falling weight deflectometer (FWD), GeoGauge, and Portable FWD], nuclear density gauge, dynamic cone penetration, and extensive laboratory tests were performed. It was found that the initial stiffness of the treated base was found to be excessively high by FWD backcalculation. Some sections of the backcalculated base moduli were over 20.7 GPa. This indicates that the layer is excessively brittle for a base material, similar to lean concrete. Six specimens (that were made without a mellowing period) exhibited cracks. There was no cracking for six specimens that had two days of mellowing. It was concluded that the culprit of the transverse cracking in the main lanes was the shrinkage of lime treated base layers. The longitudinal cracks are related to the edge drying and the transverse cracks are related to the insufficient mellowing period. Based on the findings of this study, the District implemented a 2-day mellowing period for Quicklime treated caliche base. Three newly constructed pavements (age 8, 5, and 2 months) were surveyed. No cracking can be observed so far, and the District thinks the cracking problem has been mitigated by the 2-day mellowing period. Without the mellowing period, cracking had normally occurred 1 to 2 months after construction.

Calibration of Nonnuclear Density Gauge Data for Accurate In-Place Density Prediction

Hot-mix asphalt (HMA) density is an important acceptance quality characteristic, which involves in situ tests for quality control and assurance (QC/QA). Highway agencies have conventionally used nuclear density gauges or core samples for mat density. More recently, alternate nondestructive testing methods have been considered to replace current test methods. Nonnuclear density gauges offer rapid testing while eliminating safety risks and costs associated with radioactive license. Although agencies have evaluated them, they are not implemented in acceptance testing so far. Results are presented from a field evaluation of three nonnuclear density gauges—PaveTracker, PQI 300, and PQI 301—conducted on Wisconsin Department of Transportation (WisDOT) paving projects. The main goal was to evaluate the performance and effectiveness of non-nuclear gauges for use in QC/QA activities by WisDOT. The study involved field tests at 16 project sites and included 21 mix designs and a variety of mix design and pavement design parameters, such as aggregate type, nominal maximum aggregate size, layer thickness, design traffic, and base type. Density measurements were recorded at 30 test points at each site with one nuclear gauge and three nonnuclear gauges. Although the mean standard deviation values of the nonnuclear gauge data were less than those of the nuclear gauge measurements, a consistent bias was observed between the two data sets. This bias was adjusted by using a calibration factor to yield density predictions statistically the same as the nuclear gauge measurements. It is recommended that a calibration factor determined from 10 points by using a slope function be implemented for agency use. Further, daily calibration for each mix design is recommended when the project involves multiple paving days.