Non-nuclear Density Research Articles

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

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

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

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

Theoretical and Experimental Investigation on Dynamic Response of Asphalt Pavement Under Vibration Compaction

This study aims to investigate the dynamic response regulation by combining the theoretical analysis and field test under the vibration rolling condition. Based on the viscoelastic theory of a multilayer system, the dynamic stiffness method (DSM) incorporating multidimensional Fourier transform is proposed to solve the 3-dimensional (3D) dynamic response of pavement under vibration compaction. The stiffness matrix of each pavement layer and the global stiffness matrix of the whole pavement structure are obtained. By combining vibration load with boundary conditions, the 3D exact solution is obtained and validated by the finite element method. In addition, the field test is also conducted using a series of sensors and equipment (e.g., SmartRock sensor, acceleration sensor, temperature sensors, and non-nuclear density meter) to calibrate the theoretical model to determine the wave number and dynamic modulus during the vibration rolling process. Then, considering the factors during compaction, the rules of displacement variation and pavement acceleration are investigated in terms of modulus, thickness, and density. The results show that the 3D displacement and acceleration components both vibrate with high frequencies during compaction, and peak acceleration in the vertical direction prevails. For the vertical displacement, its distribution beneath the drum of the roller is almost even except that it drops to zero abruptly around the drum edge. The relationship between thickness and acceleration follows a linear function, and the acceleration on the pavement surface rises when the thickness increases. Although the density and modulus increase with rolling times, the effect of modulus on acceleration is more obvious and prominent than that of density. In summary, the DSM presented in this article provides a robust method to calculate the dynamic response of pavement under vibratory compaction and to back-calculate the modulus of compacted pavement layers. Moreover, the regulation also sheds insight on the understanding of vibration compaction mechanism that there is a potentially strong correlation between compaction state, modulus, and vibration acceleration.

In-line characterisation of continuous phase conductivity in slurry flows using artificial intelligence tomography

Electrical Impedance Tomography (EIT) can be applied to monitor a variety of mineral and chemical processes including: velocity measurements in drilling cuttings and hydrocyclone operations. Hydraulic conveying systems rely upon the knowledge of slurry density to ensure efficient transportation of the solids. Typically, density measurements exploit the attenuation of gamma ray photons which poses complex safety, operational and regulatory concerns with Electrical Impedance Tomography affording a non-nuclear alternative to traditional approaches. To optimise the accuracy of this non-nuclear density measurement, the electrical conductivity of the aqueous phase in a multi-component slurry, is required. Whilst conductivity probes are sufficiently accurate, there are often drawbacks and limitations due to installation restrictions, as it is difficult to separate aqueous and solid phases in real-time. Electrical Impedance Fingerprinting (EIF), is a novel measurement technique which characterises formulation properties, in-situ, based upon electrical impedance sensing and artificial intelligence algorithms. This paper outlines the development of EIF and its application to monitor aqueous phase conductivity in multi-component slurries, containing sands and clays. EIF accurately predicts this conductivity with high accuracy and a root-mean squared error of 0.055 mS cm−1. This development ensures accurate non-nuclear density measurements (<5%) are obtained across an extended aqueous electrical conductivity range of 1.5–70 mS cm−1. This encompasses the majority of target hydraulic conveying systems in mining operations. EIF also enhances the functionality of ‘traditional’ electrical tomography as not only are mineral processes able to be visualised, but the process materials are simultaneously characterised, to improve process understanding, optimisation and control.

Artificial Neural Network-Based Method for Real-Time Estimation of Compaction Quality of Hot Asphalt Mixes

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.

Efficacy of Non-nuclear Methods Used for Hot Mix Asphalt Density Determination

This paper presents research efforts with a major purpose of determining if electromagnetic, non-nuclear density gauges (NNDG) are competent enough for asphalt density measurement in comparison to the already existing standard core method (AASHTO T-166). Field, as well as laboratory studies, were conducted to assess the abilities of available non-nuclear devices as they need the appraisal for future use in many developing countries including Pakistan. NNDG data collected from 45 locations, compared to density determined in the laboratory for the cores extracted from the same location, shows that the results obtained from both the methods are comparable. Laboratory studies conducted on the slabs of open and dense gradations show that such an instrument performed well for dense gradation in comparison to open ones. The Calibration effect of the instrument has a valuable impact on the accurate density determination. Results indicated that such gauges are seriously affected by moisture presence on the surface of testing pavement. Moreover, the temperature dependency of non-nuclear gauges is among the major outcome of this research. Overall the performance of such gauges is valuable, and the results are comparable to the standard results of core methods. However, these results can only be used for Quality Assurance (Q.A) purposes and not for Quality Acceptance (Q.C) of the density of pavement.

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.

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.

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.

Demonstrating Innovative Technologies for the Flemish Asphalt Sector in the CyPaTs Project

In 2015, the ROAD_IT project initiated the development and demonstration of an integrated and coherent IT process control system for the Flemish asphalt sector in order to modernize existing asphalt paving technologies and to obtain real-time data to monitor pavement behavior. One of the demonstration test tracks is CyPaTs, the construction of a bicycle path built in September 2017, using innovative technologies (www.uantwerpen.be/cypats). Five technologies are described in this contribution. An asphalt solar collector (PSC) with a piping system was installed directly in the asphalt. Cold water during summer season and hot water in winter season running through the pipes, keep the asphalt structure in a better temperature interval, avoiding rutting and cracking. Other advantages of this system are: energy gain, the prevention of damage to asphalt and the enhancement of traffic safety. The expected energy gain per year varies between 0.5 and 0.8 GJ/m2. About 20% of this energy is used for the operation of the asphalt collector itself. The remaining 80% can be used in nearby buildings. Fiber Bragg Grating (FBG) monitoring system was integrated in all three asphalt layers for the first time in Belgium. Two novel approaches of FBGs installation in asphalt layers were elaborated in this bicycle path: installation of FBGs in prefabricated asphalt specimens at the bottom of base layer and installation of FBGs in a saw cut of approx. 2mm in the previously constructed asphalt layer. The results proved a survival rate of the FBGs of 100%. The obtained strain and temperature data from FBG monitoring system has proved to be an excellent approach to establish and reflect the real condition of the asphalt pavement behaviour in time at different temperatures. The temperatures of the asphalt pavement during construction were followed up by the infrared thermography measurement techniques: a thermographic line-scanner (PAVE-IR by Moba AG) which was mounted at the back of the finisher and a hand-held IR camera (FLIR T640) was used for taking pictures every 2 meters. A real-time temperature contour plot of the pavement during construction was created to monitor asphalt pavement temperatures for quality inspection during the paving process or for later assessment. Two other non-destructive technologies for quality assessment were applied during this project. At first, the thickness was measured using aluminium plates and the MIT-SCAN T3. The obtained values were compared with topographic height measurements. Secondly, the density was measured with the PQI-380 non-nuclear density meter at several spots. The objective here is to check the density of the bicycle path, as well as the accuracy and investigate different parameters that influence the variations of the results, in particular the temperature dependency.

The use of a non-nuclear density gauge for monitoring the compaction process of asphalt pavement

The mechanical performance of an asphalt pavement affects its durability – thus carbon footprint. Many parameters contribute to the success of a durable asphalt mix, e.g. material selection, an accurate mix and even the road design in which the asphalt mix quality is quantified. The quality of the asphalt mix, by its mechanical properties, is also related to the compaction degree. However, and specifically for high volume rates, the laying process at the construction site needs an effective method to monitor and adjust immediately the compaction quality before cooling and without damaging the layer, which is now absent. In this paper the use of a non-nuclear density gauge (PQI – Pavement Quality Indicator) is evaluated, based on a site at Brussels Airport. Considering the outcome of the present research, this PQI is advised as a unique tool for continuous density measurements and allow immediate adjustments during compaction, and decreases the number of core drilling for quality control, and as a posteriori asphalt pavement density test where cores are prohibited. The use of PQI could be recommended to be a part of the standard quality control process in the Flemish region.

Accurate detection method for compaction uniformity of asphalt pavement

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 1.5m, and the reasonable longitudinal detection space is 50m. 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.

Laboratory and Field Investigation of Mechanistic Properties of Foamed Asphalt Recycled Base Course Materials for High Volume Pavements in India

The quality of cold in-place recycling (CIR) is strongly dependent on the capability of proper laboratory investigation and design, and quality control during construction. The objective of this study was to evaluate the quality of the first major foamed asphalt CIR recycled layer in India, laid on a national highway in India. A nonnuclear density gauge (NNDG) and a portable seismic properties analyzer (PSPA) were utilized to determine the density and stiffness of the foamed asphalt recycled layer. In addition, cores and material samples from the recycled layer were also tested in the laboratory for density and stiffness using dynamic modulus tests and the seismic method. The results of tests were related to material properties and critical factors influencing the performance-related properties were identified. Comparisons between laboratory and field sample data were made. Foaming temperature and gradation control of crusher dust were identified as parameters requiring tight control to achieve the required quality. The detrimental effects of excess blending of cement were also revealed. The NNDG and the PSPA were found to be capable of identifying poor quality areas both in midsections and at joints, and to be capable of monitoring the quality of recycled layer.

The Application Research of Non-Nuclear Density Gauge Electromagnetic Technology in the Road Engineering

In order to ensure the control degree of compaction and meet the design requirements in the process of asphalt pavement construction, reduce the core detection for the damage in the late. It using non-nuclear density gauge to test density, and carries on the comparative analysis with the density of core test data or conversion degree of compaction data, then study the variation regularity of after the calibration for field dynamic control compaction with the roller compaction times, Conclusion non-nuclear density gauge control accuracy and error causes in the asphalt layer compaction testing. Experiment results show that non-nuclear density gauge must be proper calibration, which according to different structure layer, gradation type and different materials and core calibration method test values. At the same time suggest appropriate to increase the number of calibration for 10~15 points, which reduce error and test error for choosing, make its accuracy of control within 2%. The conversion relationship between detecting the density and the water method to testing compaction were emphatically studied, this provides a basis for non-nuclear density gauge effective application in the field compaction test grade road asphalt layer.

The Research of Non-Nuclear Density Gauge on the Detection of Airport Asphalt Pavement Surface

To ensure the asphalt pavement construction process controls the degree of compaction to meet the design requirements, reducing late detection of road surface drill core damage. Using non-nuclear density gauge the density testing, and with the translation of core drilling to test the degree of compaction density and comparative analysis of the data, and then study the dynamic control for field calibration after compaction degree variation with rolled several times, non-nuclear density gauge summary control accuracy at the time of detection of the degree of compaction of asphalt surface and generating an error. The test results show that non-nuclear density gauge must be for different structural layer, grading types and different materials, combined with core drilling method to test the value of a reasonable calibration, the calibration also proposed modest increase in the number of 10 to 15 points, in order to reduce errors and test site selection error to precision control in less than 2%. Studied the conversion between non-nuclear density gauge and water weight method to test the degree of compaction between the non-nuclear density gauge is effectively applied across the country level surface layer of asphalt compaction scene detection to provide evidence.

Research on the Influence of Temperature and Humidity to Asphalt Pavement Seedless Detection Technology

In order to study the asphalt pavement testing compaction technology accuracy with the non-nuclear density gauge. Pave TrackerTM Plus 2701-B is used to research the influence of temperature and humidity, and Construction dynamic detection technology and methods is established basing on 2701-B,And the type of mixture was studied. It is found that, because of the difference of temperature and humidity, the result of Compaction degree has the large variability, the increased with temperature and humidity, especially humidity affects more significant. Finally, the non-nuclear detection technology method of asphalt pavement is established, this paper presents adopting the temperature and humidity compensation or increasing the number of calibration samplesisand and testing used to make up accuracy, which can effectively improve the service performance of airport asphalt pavement.

Surface Structure of Asphalt Pavement Non-Nuclear Density Gauge Density Test Results the Impact Analysis

In order to study the influence degree of the different asphalt mixture surface texture structure to the test of Non-nuclear density gauge(Pave Tracker™ Plus 2701-B). This thesis utilized non-nuclear density gauge and surface sanding method for different types of mixtures were compacted density and surface texture depth test. The results showed that: It can produce certain effect, and with it the inhomogeneity of the increases. This is mainly about mixture gradation type, among them SMA-13 affect the minimum, AC-20 take second place, ATB-25 maximum. However, using the surface sand can effective to reduce its impact. So, recommendations for ATB-25 type mixture can be used to detect the surface sand, and the SMA-13 and AC-20 are not used.

Framework for Empirical Process to Improve Nonnuclear Gauge Performance in Hot-Mix Asphalt Pavement Construction

Nuclear technology has long been used as a nondestructive method to measure the density of hot-mix asphalt (HMA) during pavement construction. Due to nuclear technology’s high costs and intense regulations associated with safety and security, several researchers have introduced and evaluated nonnuclear technologies for measurement purposes. However, no proven evidence has emerged that nonnuclear gauges can replace nuclear gauges when quality assurance (QA) is considered. Thus, this study developed a framework for an empirical process to improve nonnuclear gauge performance for use in QA and for improving the current quality control (QC) process. Data were collected by coring using a nuclear gauge and using a nonnuclear gauge from 13 HMA paving construction sites over 2 years. A new calibration method was developed for nonnuclear density gauges. The research results reveal that the proposed framework can improve the accuracy of nonnuclear gauges, which can be used for QC and QA of HMA pavement during construction. In addition, nonnuclear gauges showed significant cost savings compared to nuclear gauges from a life-cycle cost analysis.

Thermography-Driven Distress Prediction from Hot Mix Asphalt Road Paving Construction

This research was conducted to assess the effects of temperature segregation in hot-mix asphalt (HMA) paving construction on pavement distress in the early stages of its life cycle. Several paving projects across Nebraska were visited in which sensory devices were used to test how density, moisture content within the asphalt, material surface temperature, internal temperature, wind speed, haul time, and equipment type, contribute to temperature differential. Areas of high temperature differential were identified using an infrared thermal camera. A nonnuclear density device was also used to record how lower temperature asphalt density correlates with a more consistent hot area. The location was marked digitally with a handheld global positioning system to locate points of interest for future site revisits to verify research findings. The research findings indicate that among the investigated variables, truck types and density are highly correlated with temperature differential. Additionally, analysis of data from revisits after one or two freeze-thaw seasons shows that higher temperature differential is significantly correlated with premature distress of paved HMA roads while they are still in new condition. This finding suggests that higher temperature segregation created from paving construction in the zone of freeze-thaw cycles promotes visible surface distress in the very early stage of the pavement life cycle.

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.