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PURPOSES : This study aims at evaluating the use of an electromagnetic density gauge (EDG) to measure the in situ density and air-void content of asphalt concrete (AC) pavement. METHODS : In situ AC pavement density and air-void readings were obtained from two sites (Daegu and Ulsan) using an EDG. Calibration of the EDG was conducted by first obtaining density values at three different positions, on each pavement where core samples were extracted afterward. The core samples were then tested to obtain laboratory density and air-void values. The density measured using the EDG was then subtracted from the laboratory values to obtain the offset calibration values, which were then adopted to calibrate the in situ measurements using the EDG. Moreover, to analyze the effect of moisture on the pavement surface, EDG measurements were conducted under dry and wet conditions to compare the in-situ readings. RESULTS : The in-situ density readings of AC tend to be higher in moist/wet conditions. By applying the calibration value to the EDG readings, the density error percentage was reduced from 0.61% to 0.096%, and 0.64% to 0.16% for Daegu and Ulsan sites, respectively. Consequently, the air-void content error percentage was reduced from 12.8% to 1.04%, and from 10.07% to 1.78% for Daegu and Ulsan sites, respectively. CONCLUSIONS : The electromagnetic density gauge (EDG) is an effective tool for the non-destructive measurement of in situ pavement density. By applying offset calibration values, the error in the field readings was reduced, and the accuracy of the EDG measurements was improved.

The impact of machines on forest soils is regularly assessed and quantified using absolute bulk density, which is most frequently obtained by soil cores. However, to allow for repeated measurements at the exact same locations, non-destructive devices are increasingly being used to determine soil bulk density and moisture content in field studies. An example of such a device is a nuclear moisture and density gauge (NMDG), originally designed as a control measurement for soil bulk density and moisture content in geotechnical applications. Unlike road construction or foundation projects that use mineral soil or gravel, forest soils have complex structures and the presence of organic matter, which can skew moisture and density readings from a NMDG. To gain further knowledge in this respect, we performed controlled tests in a sandbox to quantify the influence of varying amounts of saturated organic matter (3, 5, 10, and 15%) mixed with mineral soil in different layers (0–5, 0–10, 0–20 and 0–40 cm) on the accuracy of soil moisture content obtained by a NMDG and soil theta probe at varying depths. Main results illustrated that the presence of saturated organic matter per se was not problematic but moisture content overestimations and related underestimation of dry bulk density occurred when the tested measurement depth was below the created organic layer. Since forest soils often exhibit higher organic matter contents in the upper horizon, correction factors are suggested to minimize the moisture content variations between NMDG and reference method. With the use of correction factors, NMDG can present a non-destructive, fast, and accurate method of measuring soil moisture and bulk density in forestry applications.

Soil bulk density and moisture content are dynamic properties that vary with changes in soil and field conditions and have many agricultural, hydrological and environmental implications. The main objective of this study was to compare between a soil core sampling method (core) and the CPN MC-3 EliteTM nuclear gauge method (radiation) for measuring bulk density (ρB) and volumetric moisture content (θv) in a clay loam soil. Soil ρB and θv measurements were determined using the core and radiation methods at 0 - 10 and 10 - 20 cm soil depths. The mean values of soil ρB obtained using the core method (1.454, 1.492 g·cm−3) were greater than those obtained using the radiation method (1.343, 1.476 g·cm−3) at the 0 - 10 and 10 - 20 cm depths, respectively. Mean ρB and θv values averaged across both depths (referred to as the 0 - 20 cm depth) measured by the core method were 4.47% and 22.74% greater, respectively, than those obtained by the radiation method. The coefficients of variation (CV) of soil ρB values measured by the core method were lower than the CV values of those measured by the radiation method at both depths; however, the CV’s of ρB values for both methods were larger at the 0 - 10 cm depth than those measured at the 10 - 20 cm depth. Similarly, the CV values of soil θv values measured by the core method were lower than the CV values of those measured by the radiation method at both depths. There were significant differences between two methods in terms of ρB and θv, with the core method generating greater values than the radiation method at the 0 - 20 cm depth. These discrepancies between the two methods could have resulted from soil compaction and soil disturbance caused by the core and radiation techniques, respectively, as well as by other sources of error. Nevertheless, the core sampling method is considered the most common one for measuring ρB for many agricultural, hydrological and environmental studies in most soils.

Intelligent compaction technology is a new pavement compaction control technology. In order to research the reliability of intelligent compaction technology for compaction degree evaluation of asphalt pavement, the intelligent compaction technology was used to compact the asphalt mixtures of Ji-shuang highway project (SMA-13 for upper layer of the pavement and AC-20 for middle layer of the pavement). The vibrating compaction value (VCV) was detected by the intelligent compaction system continuously during the rolling process. Then the compaction degree of the two pavement layers after the last vibration rolling was measured by the non-nuclear density gauge. Finally, the relationship between VCV value and compaction degree of the two pavement layers was fitted by the least square method. Results show that the compaction uniformity of asphalt pavement is good through intelligent compaction. The VCV obtained from the intelligent compaction has a good correlation with the compaction degree.

Compaction is an important standard in evaluating the quality of earth filling work. The EDG, an electrical density gauge, is a new type of fast and nondestructive compaction detection equipment. It is used to test the dry density and water content of the soil by establishing a soil calibration model while the accuracy of measurement is mainly based on the precision of equation of calibration model. In this paper, the factors affecting the accuracy of the soil calibration model were studied by an indoor calibration test, and soil samples were prepared to verify the accuracy of the soil calibration model. The test results showed that the dry density range, water content range, and sample quantity 13 samples of soil had a significant influence on the correlation coefficient (R2) of the equation of the soil calibration model. In addition, when using the calibration model with different sample numbers and sample combinations but similar correlation coefficients to test multiple groups of density and moisture content, there are also differences in the expected value and standard deviation of the error probability curve of the test results. In the engineering practice, the reasonable sample quantity was determined by the applicable range of dry density and water content obtained from the measurement error analysis of the soil calibration model.

With the advancement of intelligent compaction technology, real-time quality control has been widely investigated on the subgrade, while it is insufficient on asphalt pavement. This paper aims to estimate the real-time compaction quality of hot mix asphalt (HMA) using an artificial neural network (ANN) classifier. A field experiment of HMA compaction was designed. The vibration patterns of the drum were identified by using the ANN classifier and classified based on the compaction levels. The vibration signals were collected and the degree of compaction was measured in the field experiment. The collected signals were processed and the features of vibration patterns were extracted. The processed signals were tagged with their corresponding compaction level to form the sample dataset to train the ANN models. Four ANN models with different hidden layer setups were considered to investigate the effect of hidden layer structure on performance. To test the performance of the ANN classifier, the predictions made by ANN were compared with the measuring results from a non-nuclear density gauge (NNDG). The testing results show that the ANN classifier has good performance and huge potential for estimating the compaction quality of HMA in real-time.

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.

The 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 expensiv...

This paper proposes a computer vision system for reading analog gauges at a power substation. The gauges mentioned in this paper include oil level gauges, winding temperature gauges and SF6 gas density gauges. We present two different algorithms since an oil level gauge has different characteristics from a winding temperature gauge or an SF6 gas density gauge. For the oil level gauge, a color segmentation method is used to detect the pointer. Then we use Canny Edge Detector in combination with the Hough Circle Transform method to detect scale marks. Based on the position of the pointer and the marks, we detect the indicating value of the gauge. For winding temperature gauges and SF6 gas density gauges, we find the direction of the pointer based on the geometry properties of a double-edged pointer. With this information, we can calculate the value indicated on the gauge face using interpolation between the direction of the pointer and the value of the gauge. The system error is almost zero in case of an oil level gauge and remains low in the case of a winding temperature gauge and an SF6 gas density gauge. Mobile robots integrated with this computer vision system will work faster and more accurately than humans and will also help avoid dangerous accidents.

Porosity is one of the key properties of fluvial sediments. It is defined as the ratio of pore volume to total volume. In river science, porosity is often assumed to be spatially constant, which might be a gross simplification of reality. Ignoring the spatial variations in porosity can cause errors in morphological, ecological, hydrological, hydrogeological and sedimentological applications. Although detailed information about spatial porosity variations can be obtained from porosity measurements at field sites, such information has never been collected where these variations might be important. In this study, field porosity measurements were carried out to quantify the magnitude of the spatial porosity variation for four different sedimentological environments of a braided river: a confluence, a tributary delta, a braid bar and a secondary channel. A nuclear density gauge was used for the measurement of porosity. The nuclear density gauge proved to be a time‐saving and labour‐saving technique that produces accurate porosity values with a root mean square error of 0.03. The four sedimentological environments showed significant differences in porosity, with mean porosity being lower for confluence and bar than for delta and secondary channel. Semi‐variogram analysis showed the absence of any spatial correlation in porosity for distances beyond 4 m. This shows that distance cannot be used as a parameter for porosity extrapolation in a fluvial system unless the extrapolation distance is less than 4 m. At least eight measurements of porosity are required to obtain a reliable estimate of mean porosity in a sedimentary environment, i.e. with uncertainty, Deutsche Forschungsgemeinschaft

Traditionally, densities of newly built roadways are checked by direct sampling (cores) or by nuclear density gauge measurements. For roadway engineers, density of asphalt pavement surfaces is essential to determine pavement quality. Unfortunately, field measurements of density by direct sampling or by nuclear measurement are slow processes. Therefore, I have explored the use of rapidly-deployed ground penetrating radar (GPR) as an alternative means of determining pavement quality. The dielectric constant of pavement surface may be a substructure parameter that correlates with pavement density, and can be used as a proxy when density of asphalt is not known from nuclear or destructive methods. The dielectric constant of the asphalt can be determined using ground penetrating radar (GPR). In order to use GPR for evaluation of road surface quality, the relationship between dielectric constants of asphalt and their densities must be established. Field measurements of GPR were taken at four highway sites in Houghton and Keweenaw Counties, Michigan, where density values were also obtained using nuclear methods in the field. Laboratory studies involved asphalt samples taken from the field sites and samples created in the laboratory. These were tested in various ways, including, density, thickness, and time domain reflectometry (TDR). In the field, GPR data was acquired using a 1000 MHz air-launched unit and a ground-coupled unit at 200 and 500 MHz. The equipment used was owned and operated by the Michigan Department of Transportation (MDOT) and available for this study for a total of four days during summer 2005 and spring 2006. The analysis of the reflected waveforms included “routine” processing for velocity using commercial software and direct evaluation of reflection coefficients to determine a dielectric constant. The dielectric constants computed from velocities do not agree well with those obtained from reflection coefficients. Perhaps due to the limited range of asphalt types studied, no correlation between density and dielectric constant was evident. Laboratory measurements were taken with samples removed from the field and samples created for this study. Samples from the field were studied using TDR, in order to obtain dielectric constant directly, and these correlated well with the estimates made from reflection coefficients. Samples created in the laboratory were measured using 1000 MHz air-launched GPR, and 400 MHz ground-coupled GPR, each under both wet and dry conditions. On the basis of these observations, I conclude that dielectric constant of asphalt can be reliably measured from waveform amplitude analysis of GJPR data, based on the consistent agreement with that obtained in the laboratory using TDR. Because of the uniformity of asphalts studied here, any correlation between dielectric constant and density is not yet apparent.

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.

This paper analyses the destructive and non-destructive methods for checking the degree of compaction of asphalt layers and their multi-criteria evaluation. The data obtained during laying of ACO 11+50 mm thickness was selected for the analysis. The bulk density was determined by using probes Troxler 3440, Troxler 2701 and from the drill cores in these given locations. According to the analysis accuracy, the probe Troxler 2701 used to determine the final degree of compaction of the construction asphalt layer and for the routine control of compaction is not suitable, even though when applying AHP (Analytic Hierarch Process) it was assessed as the second most suitable one.

This 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...

This article investigates alternatives for soil compaction testing to potentially replace the standard nuclear density gauge by examining alternate testing devices and methods. Gauge reproducibilit...

Results from a recent study indicated that compaction by vibratory roller can be made more time- and energy-efficient by operating at a vibration frequency close to resonance. In this paper, the re ...

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, 36 HMA 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.

Earthwork and unbound aggregates, are among the most critical components of the construction of transportation infrastructures. Their structural performance can only be assured with appropriate quality management to ensure the materials used are similar to the ones selected in design stage, proper processing of the material to ensure that the materials are uniformly mixed and contain appropriate amount of moisture before compaction, and proper compaction equipment to ensure adequate density and stiffness. The primary tool for quality management is currently a density gauge to ensure that proper density, and in some instances moisture content, are achieved during construction. However, in-situ nondestructive testing (NDT) devices that estimate the stiffness parameters of constructed pavement layers have been emerging over the past decades. Such stiffness parameters are more representative of the structural performance, predicted during the mechanistic-empirical based design process. This paper summarizes a series of laboratory and small-scale evaluations to establish a mechanistic approach for quality management of compacted geomaterials. A synthesis of current state of practice is followed by the evaluation of two nondestructive testing devices during controlled laboratory conditions. The small-scale results were interpreted to represent the moisture and stiffness variations in the field. Based on the results of a range of geomaterials, a mechanistic-based quality management framework was developed.

Measuring the wax deposition inside pipelines is one of the critical parameters in the oil, gas and petrochemical industries to control the flow through the pipelines. This paper presents a novel method using artificial neural networks to measure the thickness of the wax. This method was based on counting the backscattered gamma-ray from different thicknesses of the wax inside the pipes with different diameters. For this purpose, the system was simulated by MCNPX code and the designed setup was optimized. The main analyses were based on the simulation results but the verification was performed using a real experimental setup. The results showed a good agreement between the simulation results and the experimental data with a root mean square error less than 1%. Response of the detector was simulated for a standard industrial nominal pipe ranged from 2 to 4.5 inches and for radiation sources 137Cs and 60Co. Using these data, a multilayer perceptron for different energy sources was trained. The best prediction of the wax thickness was obtained for the case of using two radiation sources, simultaneously. The output of the trained neural network showed that the proposed method is capable of measuring the wax thickness inside the pipe with a good accuracy.

For decades, nuclear density gauges have been used to measure the density and moisture content of soil during compaction testing in road and embankment construction. Worldwide regulatory agencies consider nuclear density gauges as controlled devices because of their inclusion of radioisotope sources. Regulatory requirements, such as the need for licensing, special storage, special transportation procedures, gauge operator training, and personal dosimetry, have become burdens for gauge users. Recently, a new nuclear density gauge for measuring soil wet density was declared exempt from licensing and other nuclear regulatory requirements in the United States. The new gauge uses an extremely low-activity radioisotope source. It further incorporates a separate probe operating on electromagnetic principles for soil moisture measurement or any other moisture measurement method the user desires. This paper presents the design features and measurement properties of this low-activity nuclear density gauge and its associated moisture probe. The measurement properties were determined from laboratory and field studies that were conducted in North Carolina, United States. These studies showed that the sensitivity and precision of wet density measurements made by the low-activity nuclear density gauge were similar to those made by a conventional nuclear density gauge. The wet density measurements made by the low-activity gauge and conventional gauge showed a strong correlation and agreement. For the two field sites studied, a silty sand subbase and a cement-treated aggregate base course, the dry density agreement between the low-activity nuclear density gauge/moisture probe and the conventional nuclear density gauge was within 3 lb/ft3 (48 kg/m3).

To evaluate the compaction uniformity effectively, firstly, the feasibility of using density and void distribution as compaction uniformity evaluation index was demonstrated by laboratory test. Secondly, relying on the project of Tong-Xun Highway, reasonable detection interval of non-nuclear density gauge PQI was determined, and quantitative evaluation index of density distribution uniformity was also proposed. Next, core samples at representative density point were drilled and of which the voids distribution characteristic on sectional image of core sample was analyzed by image processing technology, and further on, the evaluation index of void distribution uniformity was put forward. Finally, the accurate detection method of compaction uniformity based on density and void distribution was exampled relying on entitative engineering. The results show that it is feasible to evaluate the compaction uniformity of asphalt pavement with its density and void distribution. The reasonable lateral detection interval of PQI is 1.5 m, and the reasonable longitudinal detection space is 50 m. Density statistical index such as Sr, SR, k and h can reflect the density distribution uniformity on detection section. Voids number uniform coefficient UCN and voids ratio uniform coefficient UCR of core samples can reflect the compaction uniformity of asphalt pavement from the aspect of micro structure.

Modern compaction equipment can be outfitted with sensors that allow for real-time monitoring of the compaction process, an approach that is commonly referred to as continuous compaction control (CCC). This paper describes the results from an experimental research study that was conducted to assess the effectiveness of CCC technology for construction of a roadway embankment using a sand containing a significant percentage of silty fines. During embankment construction, simultaneous machine drive power (MDP) and compactometer value (CMV) measurements were recorded, along with the corresponding position of the roller. Location-specific in situ “spot tests” were also performed to independently assess soil compaction, including nuclear density gauge (NDG) tests, soil stiffness gauge (SSG) tests, light weight deflectometer (LWD) tests, and dynamic cone penetrometer (DCP) tests. A comparison of the CCC measurements with the location-specific in situ test results was performed using spatial data analysis tools and statistical regression. The measured data, spatial and regression analysis approaches, and associated discussion that are presented provide valuable information for researchers and practitioners that are considering the use of CCC technology.

The U.S. Army Engineer Research and Development Center validated the effectiveness of the TransTech Combined Asphalt Soil Evaluator (CASE) electrical impedance gauge and the Troxler eGauge hybrid electric-nuclear gauge as suitable replacements for nuclear density gauge (NDG) technology. Comparisons of soil density and moisture content were made between the gauges for six distinct soil types at varying densities and levels of moisture content. 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. Full-scale test sections ranging from crushed limestone to fat clays were constructed for the soil evaluations. Results indicated that wet and dry densities obtained with the eGauge very closely matched those of the NDG, with a coefficient of determination (R2) of approximately 94%, but with an R2 of 85% for the measured moisture contents. The calibrated CASE unit's comparison with the NDG moisture content was excellent, with an R 2 of 98%, but the R 2 values were much lower than those of the eGauge for its dry and wet density, at 83% and 59%, respectively. Further, an average R2 of only 30% was found for the CASE unit's ability to capture changing wet density during construction operations, versus 80% for the eGauge. On the basis of the Engineer Research and Development Center findings, the eGauge is recommended as the better replacement for the NDG for wet or dry density measurements. It also requires little to no calibration and has no transport or licensing restrictions.

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.

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.

Asphalt pavement compaction quality control and quality assurance (QC/QA) are traditionally based on destructive drilled cores and/or nuclear gauge results, which both are spot measurements representing significantly less than 1 percent of the in-service pavement. Ground penetrating radar (GPR) is emerging as a tool that can be used for nondestructive continuous assessment of asphalt pavement compaction quality through measuring the pavement dielectric constant. Previous studies have established that asphalt pavement dielectric constant measurements are inversely proportional to the air void content for a given asphalt mixture. However, field cores are currently required to calibrate the measured dielectric constant to the pavement density. In this paper, a method is proposed to eliminate the need for field calibration cores by measuring the dielectric constant of asphalt specimens compacted to various air void contents. This can be accomplished with a superpave gyratory compactor (SGC), which is routinely used in the pavement industry to fabricate 6 in. (15.2 cm.) diameter specimens. However, this poses difficulties with the GPR antenna height, direct coupling, and the Fresnel zone in relation to the asphalt specimen dimension limitation. These challenges are overcome by employing a plastic spacer with a known dielectric constant between the SGC specimen and the antenna. The purpose of the spacer is to reduce GPR wave speed so that the signal reflected from the specimen is separated from the direct coupling effects at an antenna height where the Fresnel zone of the GPR is not affected by the specimen dimension. The specimen dielectric constant can then be measured using the reflection coefficient-based surface reflection method (SR) or the pulse velocity-based time-of-flight method (TOF). Also, The Hoegh&ndash, Dai model (HD model) is demonstrated to reasonably predict pavement density based on the results of field measurements and corresponding core validation, especially as compared to the conventional exponential model. Results are presented from multiple days of paving on one project, as well as a single paving day on a project with significantly different mix properties. The agreement between the HD model, coreless prediction, and field cores shows the promise for implementation of dielectric-based asphalt compaction evaluation without the need for destructive field core calibration.

2-color QCD is the simplest QCD-like theory which is accessible to lattice simulations at finite density. It therefore plays an important role to test qualitative features and to provide benchmarks to other methods and models, which do not suffer from a sign problem. To this end, we determine the minimal-Landau-gauge propagators and 3-point vertices in this theory over a wide range of densities, the vacuum, and at both finite temperature and density. The results show that there is essentially no modification of the gauge sector in the low-temperature, low-density phase. Even outside this phase only mild modifications appear, mostly in the chromoelectric sector.

In this paper, a nuclear gauge was simulated using MCNPX and FLUKA codes. This device consists of a fluid-containing vessel, three BC400 rod plastic scintillator and a60Co gamma source. Simulation studies show that the changes in the count of each of the three detectors and the sum of their counts decrease with increasing vessel water height. The simulation results were compared with the measurement results. Comparison results show that the mean count difference between MCNPX code and experimental results is about 3% lower than FLUKA code, but the computation time using FLUKA code is approximately 2.8 times less than the MCNPX code.

When Missouri Department of Transportation (MoDOT) implemented design–build (DB) contracting, it revised its quality assurance programme and shifted most of the compaction testing to the design-builder. As a result, fewer compaction tests were performed by state personnel and the need for speedy quality control testing by the agency to facilitate construction production disappeared. This paper reports the results of a study conducted by the department to evaluate three alternatives to the nuclear density gauge (NDG) using life cycle cost analysis and cost index number theory. The study’s objective was to investigate alternative soil compaction test devices and provide input to a decision regarding whether or not MoDOT should retain or replace the NDG. Despite the NDG successful track record, the ease of employment and speed with which the compaction results are delivered comes with a price in terms of life cycle costs. The NDG is regulated by the Nuclear Regulatory Commission and entails an onerou...

This paper presents the results of the assessment of several popular guidelines and test protocols for the practical use of intelligent compaction at construction sites. In addition to the timely data processing and analysis, other practical challenges that impede the wide use of the intelligent compaction are establishing criteria for high quality compaction and relations between the in situ and roller measurements. Several test strips with varying moisture contents were constructed and evaluated to determine the best strategy to select the target intelligent compaction values. Several in situ test devices (such as nuclear density gauge, lightweight deflectometer and dynamic cone penetrometer) were used to compare the compacted layer properties with roller measurements. Considering the inherent variability of the material properties and relations between the in situ and roller measurements, an alternate approach to building test sections for estimating the target intelligent compaction value was evaluated. The alternative approach is based on quantifying the lift contribution to the intelligent compaction value. The proposed approach seems to be a good compromise between achieving a high quality compacted layer and providing enough flexibility to contractors to use their know-how in expediting the construction process.

In the traditional compaction procedure of pavement subgrade, the level of compaction is checked through spot measurements of density and moisture contents at some selected locations. Such tests can leave soft spots undetected and could result in the premature failure of the pavement. In the intelligent compaction (IC) procedure, the compaction level of the entire compacted area can be estimated in real-time. The University of Oklahoma has developed one intelligent compaction tool known as Intelligent Compaction Analyzer (ICA). This paper presents two field demonstrations for evaluating the ICA in continuously measuring the dry density and modulus of stabilized subgrades. In the first study, it was demonstrated that the ICA can estimate the subgrade density comparable to Nuclear Density Gauge (NDG) measured density. The second project verified the ability of ICA in estimating the modulus of the stabilized subgrade. The ICA estimated moduli correlates well (R 2 = 0.63) with the resilient moduli. The findings from these two demonstrations suggest that the ICA is capable of continuously measuring the density or modulus during the compaction of subgrade. Such real-time estimates of the subgrade stiffness can aid roller operators obtaining better overall quality by identifying and remediating under-compacted areas during the construction process.

Two of the most basic quality control tests made in the field during soil construction are the soil’s moisture content and density. The establishment of a uniform procedure to compare the performance of soil based on moisture and density began with E.E. Proctor in the early 1930s during highway construction in California. He found that, by simply measuring these two properties, he could determine if a soil was too dry, too wet, or too lose to perform at its peak capacity for load bearing. Later research showed that knowledge of just these two physical properties can provide further insight into the soil’s stability, strength, and fabric, allowing prediction of its future behavior under changes in load and environment. Even better, in practice, determining these two physical properties in the field has become of the simplest tests to conduct, thanks to one unique device: the nuclear density gauge.

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.

The nuclear density gauge has been the standard soil compaction acceptance method for the Missouri Department of Transportation (MoDOT) for several decades. However, the cost of licensing, security, transport protocol and training imposed by the federal government have caused MoDot to question whether it remains a cost effective testing technology.. Nuclear density testing’s rapidity and accuracy has been crucial in enabling MoDOT inspectors to keep contractor grading processes on schedule. But, in the last two years MoDOT’s Quality Management program has shifted the bulk of testing requirements to the contractor, reducing the need for MoDOT inspection on grading projects. As a result,, MoDOT is investigating compaction testing alternatives to the nuclear density gauge which can provide the necessary results at a lower life cycle cost. The investigation comprised a comprehensive review of previous research into compaction testing alternative as well as key findings and gaps in research. This led to the purchase of XX pieces of alternative test equipment which were employed simultaneously alongside the nuclear density gauge on four large structural fill projects. The field testing yielded a set of comparable test results taken at the same time, in roughly the same location, and under the same environmental conditions, and arguably making this research the most comprehensive study of compaction testing technology on record. The dissertation discusses MoDOT’s Quality Management program’s development and links to its origin in Design-Build project best practices, which provided the motivation to seek alternatives to the nuclear density gauge. Life Cycle Cost Analysis and Cost Index theory was utilized in comparing the compaction testing alternatives and presenting present cost per compaction test for the Department. For MoDOT project sites, linear and multiple regression

The moisture content of solids in some cases is measured by the same types of analyzers that are used on liquid or gas samples. The laboratory-type moisture analyzers—the oven and the Karl Fischer-type units—are also similar in their operations when used on liquid or solid samples. There are several other methods for moisture determination which involve discontinuous measurement of moisture in the sample. The moderation of neutrons by hydrogen atoms is used as the basis for moisture detection in this instrument. A nuclear density gauge is, therefore, included as part of the moisture measurement. Microwave solids moisture analyzers have been used to measure the water content of plastic powders, chips or pellets, soaps, grains, powdered clay, paper, hardboard, and plastic products. The electrical resistance of nonconducting solids is influenced by the moisture content of the sample. The phenomenon of nuclear magnetic resonance has also been exploited to build a rather expensive solids moisture analyzer.

Pavement performance is highly dependent on several factors that include: structural adequacy, material properties, traffic loading, and construction quality. The quality of subgrade or base/subbase compaction also significantly affects the performance of pavements; predominantly flexible pavements. In particular, the majority of the distresses in flexible pavements are mainly attributed to the compaction defect in these layers. In current practice, the compaction quality of these layers is usually quantified using the nuclear density gauge (NDG). However, several concerns arise due to the use of the NDG. This study was initiated with the aim of evaluating the sensitivity of the parameters measured using non-nuclear methods/devices to moisture content, compaction effort, testing time after compaction, and aggregate type. To fulfill this objective, a laboratory procedure for compacting large samples was developed. This procedure facilitated testing using three non-nuclear 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. 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 concluded that the DCP was most sensitive to detecting changes in the measured parameters. In addition, precision of the DCP was similar to other non-nuclear devices.