Pavement Test Research Articles

Study on infrared differential thermal non-destructive testing technology of the permeability of hot mix asphalt pavements

In order to non-destructive test (NDT) the permeability coefficient of hot mix asphalt (HMA) pavements fast, A methodology for assessing the permeability coefficient was proposed by infrared differential thermal testing of pavement after rain. The relationship between permeability coefficient and air voids of HMA specimen deter-mined. Finite element method (FEM) models were built to calculate the surface temperature difference with different exposure time after precipitation. Simulated solar radiation source and fully saturated plate specimens were set in laboratory, tests verify that the different exposure time the specimen surface temperature difference. Infrared differential thermal detection permeable pavement hardware and corresponding software developed. Based on many test results, the evaluation index and criteria of permeability coefficient of HMA pavements tested by infrared differential thermal were developed. The results showed that: There is correlation between air voids and permeability coefficient of HMA specimen. Permeability coefficient of HMA pavements can be determined by different surface temperature at different exposure time. 9:00 am - 14:00 pm is the best time to detect permeability coefficient by infrared differential thermal NDT. Permeable asphalt pavement permeability can be achieved by infrared detector quickly and continuously, a lane testing; Per the permeable assessment criteria, in-place pavements permeability coefficients can be accurately evaluated.

Effect of groundwater table rising on the performance of a Swedish-designed gravel road

Abstract Sweden has a wide network of gravel roads. When the water table levels rise during the freeze-thaw and wet seasons, the bearing capacity of the roads will decrease and rut depths increase. The road will suffer a small deterioration every time a vehicle travel over it. Therefore, it has been decided to investigate the long-term performance of a Swedish designed gravel road using an accelerated pavement testing facility. A trial gravel road was constructed and exposed to various levels of ground water table which simulate the weather changes in Sweden. The structure of the trial gravel road consisted of 15 cm (base and surface layer), 20 cm sub-base layer and 260 cm subgrade soil. The trial road was tested using the Heavy Vehicle Simulator (HVS) and the vertical surface deformations and the vertical dynamic deformations were measured by means of laser profile measurement and eMU coils respectively. At the end of 85 000 HVS passes, the tested road suffered from serious deformations as discussed in details in this paper. Furthermore, a transverse trench section was excavated at the end of HVS trafficking in order to investigate the possible mechanism contributing to the tested road failure.

Prediction of Subgrade CBR using FWD for Thin Bituminous Pavements

Deflection based models developed by Jameson, Roberts et al and Queensland Department of Transportation and Main Roads are commonly used for predicting the subgrade CBR of asphalt pavements. The models utilise Falling Weight Deflectometer (FWD) deflection D900 recorded at 900 mm from the centre of the loading plate. The principal aim of the study is to enhance the prediction of the in-situ subgrade CBR using FWD for granular pavements with thin bituminous layers. The scope of the study included the comparison of subgrade CBR predictions from the three deflection based models and the predictions were verified using the in-situ CBR values derived from Dynamic Cone Penetrometer (DCP) from eleven pavement test sites. The study shows that the three models over predict the subgrade CBR because the deflections recorded at sensor D900 are consistently small. It is observed the impact load has little influence on the deflection at D900 for pavements with asphalt layer less than 50 mm. The inherent non-linearity behaviour of the thin pavement structure is also the reason for the discrepancies in the predictions. Consequently, a new predictive model is developed utilising the FWD deflection D450 observed at 450 mm from the impact load.

Permanent deformation and deflection relationship from pavement condition assessment

The development of permanent deformation in flexible pavements has been a research topic for several decades. Currently there are models included in the structural design of pavements that can predict this type of failure. However, the variables required for the prediction of this distress are complex or difficult to obtain in the field, making its application in pavement evaluation also difficult. Measurement of the deflection of pavement structures by means of non-destructive testing is a technique used to assess the condition of the pavement. This research study seeks to correlate data from deflections of the pavement surface with probable permanent deformation in time. In addition, prediction of the remaining life of the pavement structure using a specified criterion is also analyzed. In order to accomplish these objectives, data acquired from 4 different full scale accelerated pavement test tracks was used to develop a permanent deformation model as a function of deflection, load repetitions and pavement layer thickness. The developed model considered a time series model that incorporates an Auto-regressive parameter of order 1. The proposed model presents an advantage over currently available models because it reduces the required parameters to predict the permanent deformation and/or remaining life in the structure and because these variables can be easily found and updated in a pavement management system.

Integrating Data Collection Optimization into Pavement Management Systems

This paper describes a method for using location data to optimize the routing of pavement data collection vehicles. In much of the developed world, pavement testing is performed on a regular basis; the pavement testing data, in turn, serves as input to Pavement Management Systems. Currently, in the United States of America, state departments of transportation plan this data collection work by providing the list of roads that must be tested and then leave the routing of the vehicles to the equipment operators who typically execute the work in an ad hoc manner. This study presents the processes required to code the list of roads for testing, select appropriate hotels in the region of testing, and apply a Traveling Salesman Problem with Hotel Stops model to derive a route. Applying the processes to a case study shows significant cost savings associated with this method of roadway testing, as opposed to the current ad hoc methods.

Development of a mid-depth profile monitoring system for accelerated pavement testing

This study presents the development of a new mid-depth profile monitoring system (MPMS) to investigate the rutting behavior of full-depth asphalt pavements. The scope incorporates an experimental study that uses a full-scale accelerated pavement testing (APT) facility. Two different thicknesses of full-depth asphalt pavements were constructed in the Indiana accelerated pavement-testing facility. A laser profile scanning system was designed to reconstruct the transverse profiles at each pavement layer interface throughout the process of accelerated pavement deterioration. The contribution of each pavement structural layer to the total rut depth and the evolution of layer deformation were determined. The developed system provides reasonable results with a high accuracy level based on the findings. First, the measured rutting curves at each layer interface agree well with the theoretical characteristics of rutting evolution and clearly exhibit the primary and secondary stages of rutting development. Furthermore, all the measured rutting curves have good coefficients of correlation. Second, the locations of critical rutting and the total rut depths were found to be independent of pavement thickness when the pavement is sufficiently thick, which is a finding that agrees with previous study results, the study reported the thickness threshold value to be 5.12in. (13.00cm) for their case. The results demonstrate MPMS developed in this study provides an excellent method to evaluate the rutting performance of asphalt pavements in the APT. In addition, MPMS has a potential application to in-service pavements.

Solar heating reflective coating layer (SHRCL) to cool the asphalt pavement surface

The asphalt pavement heated by solar has attracted great attentions in heating urban cities, so-called urban heat island (UHI). In fact, the solar energy heating asphalt pavements also has potential ability to bring out geological disasters in permafrost, e.g., Qinghai-Tibet Plateau (QTP). This study designed a special solar heating reflective coating layer (SHRCL) in order to cool the asphalt pavement surface. The cooling performance of SHRCLs was studied by comparing the temperatures of normal pavements and SHRCLs. The result indicated that SHRCL could work as expected resulting in reducing around 10°C compared to the normal pavement, no matter on the top or on the bottom. The temperature difference between the top and the bottom was about 5°C, not only in SHRCLs but also in normal pavements, less linking with coating or un-coating. The field testing result agrees very well with the laboratory study. To enhance the skid resistance of SHRCLs, sands were added into coatings without influencing the cooling performance, but reducing the abrasive resistance. Accelerated pavement testing (APT) was employed to evaluate the engineering performance of SHRCL. It is suggested that inhomogeneous deformation, e.g., rutting, will bring cracking and spalling between asphalt pavement surfaces and coating layers.

Pavement temperature mitigation by the means of geothermally and solar heated air

In this article, a novel method to mitigate pavement temperatures by the means of air convection is presented. The technique introduced here is based on a new type of experimental setup called a ground source heat simulator, which is able to feed air at a controlled temperature to a set of pipes embedded under a test pavement surface. The air at the chosen temperature can flow through the designed system by natural convection. The air heated by the simulated geothermal source can mitigate the pavement temperature in winter and summer conditions in order to avoid freezing and overheating of paving surfaces in an urban environment. In particular, during winter the geothermal air warms up the pavement, while during summer the pavement is cooled down. Laboratory tests of the ground source heat simulator allowed the collection of a high amount of data, which is here analysed statistically and computationally. This article shows that the use of geothermal energy to preheat the inlet air in pavements where an array of pipes is installed can provide a measurable contribution for the mitigation of pavement temperatures in both winter and summer conditions. Furthermore, the experimental data gathered successfully proved the effectiveness of computational simulations for the study of buoyancy powered air flow through channels buried under pavements and increased the understanding of the physical phenomena happening in the system under analysis. Finally, preliminary testing in the environment showed that the concept is effective and works as expected.

Cross Tension Prestressed Concrete Pavements Temperature Stresses

Temperature fields and stresses of Cross Tension Retard-bonded Prestressed Concrete Pavements (CTRPCP), which are constituted by cross tension retard-bonded prestressed concrete slabs, sand gravel sliding layers, and semi-rigid bases, are studied. First, first, second, and fourth types heat transfer boundary conditions are programmed to analysis the CTRPCP’ transient temperature fields, on ABAQUS heat transfer analysis plat form. Then, the temperature fields are imported into the mechanical model to implement coupled thermo-mechanic analysis is to obtain temperature stresses of CTRPCP. On this basis, axle force gauge and vernier caliper are installed on test pavement to measure the prestressed reinforcement axial forces and displacement changes of pavement slab end with temperature changes in typical summer cloudless conditions. By comparing with the results of numerical analysis, the rationality and accuracy of the calculation model of coupled thermo-mechanical analysis of concrete pavement are verified.

Case history study: field monitoring and performance prediction of a field-blended rubber asphalt mixture in Brazil

ABSTRACTAmong the fabrication processes available for obtaining asphalt rubber, terminal blend is the most commonly used in Brazil. On the other hand, the use of field-blended rubber asphalt has been around in the United States for decades, especially in the state of Arizona. The lack of information regarding this technique in Brazil, however, inhibits a more common use in pavement construction/rehabilitation. This case history study was conducted in order to characterise the field performance of the first pavement rehabilitation job in Brazil using a field-blended rubber asphalt mixture and attempt to predict its future performance. A 500-m test section using a field-blended rubber asphalt mixture with a gap-graded aggregate as a surface course was monitored periodically through pavement deflection tests, roughness, rutting and surface conditions. Pavement monitoring revealed good functional and structural conditions after 4 years of service life. Accelerated pavement testing (f-sAPT), conducted in a representative test section using a full scale, mobile traffic simulator, exhibited promising performance. No cracking was observed in the test section and the average maximum rut depth was below limits after simulating 7 years of service life. Results from the f-sAPT simulation were then used to calibrate the performance cracking and rutting models in the Highway Development and Management Model (HDM-4).

Evaluation of Pavement Layer Moduli Using Instrumentation Measurements

Instrumentation embedded in pavements is increasingly being used to measure the critical responses and monitor performance of specially-constructed experimental pavement sections or in-service pavements under controlled wheel loading or live traffic. On the other hand, nondestructive tests (NDT), such as falling weight deflectometer (FWD) testing, are routinely performed to evaluate pavement layer structural properties based on deflections measured on the surface of the pavements. In cases where measurements from the pavement surface only are not sufficient to infer pavement layer modulus values, e.g. rolling wheel deflectometer (RWD) tests typically with only one deflection measurement or complex geometries, a procedure that combines measurements from the embedded instruments and surface deflections would provide an alternative to the traditional backcalculation of pavement layer moduli. This study presents an inverse analysis procedure integrating finite element (FE) models and a population-based optimization technique, Covariance Matrix Adaptation Evolution Strategy (CMA-ES), to determine the pavement layer structural properties. Tests using a lightweight deflectometer (LWD) were conducted on instrumented three-layer scaled flexible pavement test sections. The time histories of the LWD load, surface deflection underneath the LWD load, subgrade deflection and vertical stress were recorded and used in the inverse analysis. While the common practice in backcalculating pavement layer properties still assumes a static FWD load and makes use of only peak values of the load and deflections, dynamic analysis was conducted to simulate the impulse LWD load. Results of the inverse analysis show that consistent pavement layer properties can be obtained based on the LWD surface deflection data and measurements of the embedded instrumentation.

Evaluating Constructed Aggregate Layers of Working Platforms and Flexible Pavements: Adequacy of In-Place Quality Control and Quality Assurance Techniques

Quality assurance is extremely important for satisfactory end performance of a constructed pavement. Traditional quality control and quality assurance (QC/QA) procedures based on volumetric and surface property checks are becoming outdated when used for constructing pavement foundation layers and ensuring pavement longevity. Recent emphasis in QC/QA procedures has shifted from a density-based approach to stiffness- and strength-based approaches with newly adopted advanced technologies. However, the need for QC/QA is often overlooked in the construction of low-volume roads with unbound aggregate layers, which may be built with recycled or out-of-specification materials of marginal quality: both are currently common sustainable practices. This paper summarizes key findings from QC/QA tests performed on full-scale pavement test sections in a recent research study conducted by the Illinois Center for Transportation. The focus of the tests was the validation of material specifications that the Illinois Department of Transportation has recently adopted for large-size unconventional aggregates, known as aggregate subgrade, through accelerated pavement testing. Seven representative aggregate types were used to construct test sections with aggregate subgrade and virgin and recycled capping and subbase layers. Density measurements from a nuclear gauge were collected and routinely contrasted with modulus results from the lightweight deflectometer and soil stiffness gauge (GeoGauge) from the constructed layers. Further, forensic strength assessment was carried out by dynamic cone penetrometer and a variable energy PANDA penetration device. Geoendoscopic imaging, coring, and trenching were also conducted to identify the depth of the water table and the thickness of the as-constructed layer. The PANDA penetrometer results, in conjunction with geoendoscopy, proved to be effective in correlating rutting performances to QC/QA test results.

Calibration of Asphalt Strain Transducers by Using Digital Image Correlation

Full-scale pavement testing often utilizes embedded instrumentation to measure the effect of traffic loading. As with any scientific measurement, confidence in the data from these sensors relies on proper calibration and installation. Manufacturers of sensors typically perform calibration tests before shipment, but these tests are not standardized. In addition, some manufacturers provide only one calibration sheet covering a batch of sensors, while others provide calibration results for each sensor. Many transducers are calibrated to produce voltage sensitivity factors; however, not all data acquisition systems accept these as inputs. This was the case at the pavement testing facility of the Minnesota Department of Transportation, where a new data acquisition system required gauge factors. This paper describes the development of a bench calibration testing procedure that uses a digital image correlation system to determine system gauge factors (SGFs) for two types of asphalt strain transducers. The calibration results clearly show that each transducer has a unique SGF that should be used when transforming collected strain data. Although the procedure that was developed produced consistent SGFs between tests, several improvements are recommended. The variations in SGFs found in this study demonstrate the need for fully understanding the calibration of strain transducers and the data acquisition systems to which they are connected.

Density Observations from a Full-Scale, Untrafficked Test Section with Guidance for Dryback Methods

This paper presents a discussion with data on factors related to the in-place density measurement of asphalt pavements. A review of the literature traces changes to asphalt density measurement technologies over the past 60 years. Two phases of investigation then are presented in which in-place density was evaluated for an ongoing study of environmental effects at a test section in Columbus, Mississippi. A series of laboratory and field activities was performed in Phase 1. In Phase 2, studies were made of laboratory drying practices of specimens that were cored after an extended period of field aging. The key conclusion from these efforts was that ASTM D7227 might not remove sufficient moisture from some specimens to achieve accurate density measurement when pavements have been exposed to moisture for extended periods of time. This paper presents a case with an average error in air void measurement of 0.9% (measured 9.1% when 10% was correct) for specimens that were cored, dried according to ASTM D7227, and then measured for mass in air 1 day later. This finding is of most concern to rehabilitation and research work in areas in which aggregates have high potential for absorption but is of no concern to new construction projects. Furthermore, the work presented here validated the use of ASTM D7227 in circumstances in which mixtures were exposed to moisture for short periods of time. The work also suggested three options to take to accurately measure in-place density for performance testing of aged pavements that contain high-absorption aggregates (i.e., dry in oven, develop correlation equations, or dry for several weeks).

Improving the GPR Detectability Using a Novel Loop Bowtie Antenna

The Ground Penetrating Radar (GPR) technique finds immense applications in civil engineering today, as the most suitable approach for non-destructive testing of pavements, highways, concrete structures, and more. The major challenge in carrying out a GPR evaluation is that the properties of the probed medium are usually unknown. The permittivity and conductivity of the medium may vary from those of air to water. The electromagnetic waves also have a frequency dependent attenuation. The ability of GPR to detect signals reflected and scattered by the targets largely depends upon the antenna performance. This paper studies a novel 11:1 wideband loop bowtie antenna with very good radiation properties in the entire operating bandwidth. Synthetic and experimental results are presented for the return loss and gain of the antenna. Furthermore, experimental results are presented for the radiation patterns in the E- and H-plane. We also used the antenna to measure B-scans over two different pipes, a bamboo, and a reinforced concrete structure. All results obtained with the proposed antenna have been compared with results obtained by using a RC loaded antenna. It has been found that the loop bowtie antenna has excellent detection capability and produces less clutter. The loop loading technique can be applied to existing antennas for improved GPR imaging. This will improve the detectability of GPR by improving the target return signal.

Deployment of the Next Generation Concrete Surface in Minnesota

Development of a quiet diamond grinding configuration commenced in an initial laboratory effort at Purdue University, followed by research iterations from 2007 to 2010 at the pavement test track research facility (MnROAD) of the Minnesota Department of Transportation (DOT). This paper catalogues the stages in the development and deployment of the Next Generation Concrete Surface (NGCS) from the configuration development at MnROAD, coupled with the simultaneous development of a tire–pavement noise predictive model deployed on Interstate 94 near Saint Cloud, Interstate 35 in Duluth, and Interstate 394 in Minneapolis, Minnesota. NGCS in these projects caused noise reduction of 3 to 6 dB, representing 50% to 75% sound intensity reduction. Diamond grinding was performed on the preexisting textures: burlap drag on Interstate Highway 94 near Saint Cloud, transverse tining on Interstate Highway 35 in Duluth, and Ultra-Thin Bonded Wearing Course (UTBWC) on Interstate 394, Minnesota DOT exceeded the goal of not increasing the pregrind tire–pavement noise level by these rehabilitations. The predictive tire–pavement interaction noise model was validated in these deployments, including on Interstate 394, where the full acoustic benefit of NGCS had been attenuated by the anomalous effect of undulations reminiscent of the previous concrete–UTBWC interface, which had inadvertently conferred a background configuration to the new diamond-ground surface.

Further Evaluation of Limiting Strain Criteria for Perpetual Asphalt Pavement Design

Perpetual asphalt pavements have been designed with single threshold values for the horizontal strains at the bottom of the asphalt concrete layer and for vertical strains on top of the subgrade to prevent the occurrence of bottom-up fatigue cracking and subgrade rutting. Several thresholds have been utilized for design based on laboratory and field test results. Limiting strain distributions were recently proposed for perpetual pavement design instead of single threshold values for controlling the horizontal and vertical strains. These design criteria were developed with data collected from test sections at the National Center for Asphalt Technology pavement test track. The objective of this study was to conduct additional analyses of eight perpetual pavement sections located in different climatic regions, to support the proposed limiting strain criteria. These sections were simulated in the PerRoad perpetual pavement design software to determine the horizontal strains at the bottom of the asphalt concrete layer and the vertical strains on top of the subgrade. The strains were then analyzed to evaluate the proposed limiting strain criteria. Based on the simulations, the limiting horizontal strain distribution above the 60th percentile can effectively differentiate the calculated strain distributions of the eight perpetual pavement sections from those of the test sections that failed due to bottom-up fatigue cracking on the test track. In addition, the calculated vertical strains on top of the subgrade at the 50th percentile were lower than the proposed 200-microstrain limit. These results provide additional support for utilizing the proposed strain criteria in perpetual asphalt pavement design.

Characterizing Cracking and Permanent Deformation; an Attempt for Predicting the End of the Structural Pavement Life

Durable, therefore sustainable, road needs to attain specific characteristics, among others, resistance to permanent deformation and cracking. Determining the development of both characteristics are important to be able to predict pavement life and performance. In this research, permanent deformation occurring in three pavement sections was measured by a transverse profilograph. The pavement sections were simple two layer structures consisting of a gravel asphalt concrete (GAC) layer on a sand subgrade. The length and the width of the section are 16 m and 4 m respectively. These three sections were tested by means of Lintrack, an Accelerated Pavement Test (APT) which allows large number of realistic wheel load applied in a limited period of time. The results of this measurements shows the development of permanent deformation, which is defined as ‘rut depth’, as function of the number of load repetitions. Using relation exists between the radius of curvature of a deflection profile and the tensile strain at the bottom of a slab, the creep/permanent strain as a result of permanent deformation was calculated. This paper is carried out to determine relations between the rut depth and the radius of curvature and between the rut depth and the creep/permanent strain. Also, cracking development was observed upon these three pavement section. The result shows that there is a rather good correlation between rut depth and permanent/creep strain which is independent of the layer thickness.

Factors Related to the Appearance of Transverse Bumps in Asphalt Overlays Placed over Crack Sealant

Crack sealants often are used as a preservation tool in asphalt pavements. These sealants are placed in cracks to prevent water intrusion into the pavement foundation. Through the reduction of water intrusion, the strength of foundation layers is maintained, and acceptable pavement performance is extended. However, when a hot-mix asphalt overlay is placed on top of a pavement that contains crack sealants, a bump and additional transverse cracks sometimes occur in the new overlay asphalt. These bumps and sometimes transverse cracks are initiated during breakdown rolling and become progressively more severe on further compaction. This paper presents the results of a 5-year study designed to identify factors that related to the appearance of these bumps and consequent cracks. The results of the study indicated that vibratory breakdown rolling, pavement gradient, sealant geometry, tack coat application rate, and tack coat adhesivity were factors that contributed most to the occurrence of bumps and transverse cracks during asphalt overlay construction over crack sealants. Observations suggested that transverse bumps and consequent cracks occurred in proportion to the size of the bow wave of asphalt concrete present immediately in front of the breakdown roller. The increase in the bow-wave size depended on asphalt mixture properties, breakdown roller size, speed, vibration characteristics, and pavement gradient. Three pavement test sections also indicated that the tack coat application rate had an effect on reduction in the appearance of transverse bumps.

Accelerated Pavement Testing in Slovakia: APT Tester 105-03-01

This article presents the APT (Accelerated Pavement Testing) facility constructed and operated by University of Zilina. The machine is designated as APT tester 105–03–01. The article describes tester's technical properties, operational capabilities, sensory equipment embedded in the pavement and data gathering procedures. The device has several unique design solutions that make it stand out from similar facilities in the world:•The principle of fixed linear APT facility with loading unit not positioned in a fixed frame, but instead, moveable along a guiding rail to better simulate traffic loading.•Loading unit consisting of fixed and movable frame held by support connected by joints for better simulation of suspension like those found on truck axles.•The construction of the electric motor, gear box and frequency inverter and its mounting system on the loading unit.•Frequency converter controlled acceleration and deceleration and speed during the movement.•Hydraulic stabilization system stabilizing the movable frame preventing the load to tip the loading unit in the acceleration and deceleration stage.•Autonomous hydraulic system placed on the outer frame able to lift the loading unit and allows for free manipulation without acting on the pavement.