Pavement Test Research Articles

Instrumented flexible pavement responses under aircraft loading

ABSTRACT The FAA National Airport Pavement Test Facility (NAPTF) is a full-scale accelerated pavement testing facility located in Atlantic City International Airport, New Jersey. Six flexible and three rigid test sections were built, instrumented and trafficked by Boeing 777 and 747 gears as part of construction cycle one. One flexible test section with an asphalt-stabilised base over a low-strength subgrade was considered in this study. All dynamic sensors, including pressure cells, strain gauges and multi-depth deflectometers were evaluated. A multistep procedure for evaluating the dynamic sensors was developed, and it included data reliability, repeatability, changes in the pavement responses under the Boeing 777 and 747 gears, and comparison with a three-dimensional (3D) finite element (FE) mechanistic model. The mechanistic model was found to predict the pavement responses with good reliability, whenever representative layer moduli are used. The study also found that 60% of the sensors produced acceptable or marginal responses and 40% produced unacceptable responses; therefore, it is recommended to consider this sensor survival rate when instrumenting future test sections. The rutting performance and pavement responses over time were evaluated; the test section was shown to have relatively similar performance and pavement responses under the Boeing 777 and 747 gears.

Desarrollar una metodología de implementación de la norma NTP-ISO/IEC 17025:2017 para la acreditación de laboratorios de ensayo de suelos, concretos y pavimentos en universidades privadas del Perú – 2018

El propósito fue desarrollar una metodología de implementación de la Norma NTP ISO/IEC 17025:2017 para la acreditación de laboratorios de ensayo de suelos, concretos y pavimentos en universidades privadas del Perú, para lo cual se utilizó como marco de referencia el PMBOK y los requisitos de la Norma NTP ISO/IEC 17025:2017.Se estructuró la metodología en tres componentes principales: diagnóstico, gestión, operación y mantenimiento, cada uno de los cuales contiene un grupo de formatos estructurados en función a los requisitos normativos a implementarse. La metodología propuesta es una herramienta de ayuda a laboratorios universitarios que aspiran acreditarse, que garanticen la calidad y confiabilidad de los ensayos y coadyuven a su gestión como centro de formación, investigación y de servicio. En el Perú son escasos los laboratorios acreditados de universidades, problema que se refleja en el posicionamiento de nuestro país en cuanto a calidad en infraestructura, en tal sentido, la metodología propuesta sería de mucha ayuda en el proceso de acreditación de laboratorios y por ende mejorar la calidad de la infraestructura.

Performance evaluation of flexible pavements with a lateritic gravel base using accelerated pavement testing

Lateritic gravel is widely used for road construction and its mechanical properties have been explored in numerous laboratory tests. In this study, full-scale accelerated pavement testing was conducted to evaluate the long-term performance of pavements constructed with lateritic gravel as the subbase and base materials. Test Sections were constructed in a test tank and instrumented with temperature sensors, strain sensors, and moisture content sensors. This study investigated two asphalt layer thicknesses (5 cm and 10 cm) and three types of base materials (crushed stone, cement-lateritic gravel, and lateritic gravel blended with crushed stone) for comparative purposes. The test pavements all had a uniform subbase depth of 30 cm of raw lateritic gravel. The development of permanent deformation and cracking was recorded periodically. Based on measurements and observations, this study found that the crushed stone base performed better than the blended lateritic base in terms of rutting and cracking resistance and that rutting development was relatively less in the thicker (10 cm) asphalt layer than in the thinner (5 cm) layer. The cement-lateritic base developed the largest rutting and exhibited the earliest appearance of cracking among the three base types and showed the weakest behavior among these three bases.

Estimating Asphalt Concrete Modulus of Existing Flexible Pavements for Mechanistic-Empirical Rehabilitation Analyses

AbstractThe modulus of the existing asphalt concrete (AC) layer, back-calculated from nondestructive pavement tests, is a crucial input for an accurate overlay design in the pavement mechanistic-em...

3D simulation of deflection basin of pavements under high-speed moving loads

The nondestructive testing of pavements currently has become more focused on continuous deflection profiles and vehicle moving speeds, which are recognized to be critical in obtaining complete and accurate pavement responses and conditions. However, current techniques cannot produce satisfactory results in terms of continuous deflection profiles at high-speed moving loads. Under this circumstance, the computational simulation is a good alternative. The objective of this study is to utilize the three-dimensional (3D) finite element (FE) analysis to investigate the characteristics of deflection basins of pavements under high-speed moving loads. Specifically, a 3D FE pavement model is constructed with six sets of pavement materials representing six types of pavements and four moving speeds (24 km/h, 40 km/h, 64 km/h, and 80 km/h). The results demonstrate that the deflection basin of a pavement exhibits an asymmetric shape under a high-speed moving load. It also reveals that there is a time lag between the maximum deflection and the center of the load in flexible pavements. This time lag is utilized to define a new term of “lag angle”. The effects of the material viscoelasticity, structural inertia damping, moving speed, and pavement deterioration conditions on the shape and lag angle of the deflection basin are illustrated. Furthermore, it is found that the lag angle of the deflection basin is closely related to the phase angle of the viscoelastic pavement materials. Finally, the deflection basins predicted by the 3D FE analysis are proven to be comparable to the field deflections obtained at a high moving speed.

Validation of the subgrade shear strength parameters estimation methodology using light weight deflectometer: Numerical simulation and measured testing data

Abstract Shear strength parameters (angle of internal friction, ϕ, and cohesion, c) of a soil medium are the key properties for the bearing capacity and stability analyses. The strength parameters have been recognized as one of the most reliable mechanical properties of pavement subgrade that can be used to estimate its permanent deformation behavior under repeated loading. In addition, when a pavement structure is subjected to a non-standard superheavy vehicle load (i.e., gross vehicle weight in excess of a few million pounds), investigation of instantaneous shear failure or onset of yielding in the pavement subgrade layer requires the knowledge of the strength parameters. Light Weight Deflectometer (LWD) has been commonly used as a Non-Destructive Test (NDT) method for in-situ determination of stiffness properties of pavement layers, unpaved roads, and subgrade layer during the construction process. In this study, the validity of a recently developed LWD-based methodology for estimating the in-situ shear strength parameters of the pavement subgrade layer has been further investigated. In this methodology, the commonly accepted hyperbolic stress-strain constitutive soil model along with the consideration of stress dependency of subgrade materials under multiple LWD load levels have been incorporated. The methodology was validated using numerically simulated LWD testing at multiple load levels for two different subgrade materials. In addition, the LWD data collected from large-scale experiments conducted at University of Nevada, Reno testing facility and National Airport Pavement Test Facility were also utilized to verify the methodology. It was found that the proposed LWD-based methodology provides a reasonable estimate for the in-situ shear strength parameters of the compacted soil subgrade.

Subsurface deformation mechanisms beneath a flexible pavement using image correlation

Flexible pavement structures are widely used in road construction, especially in circumstances where very high traffic volumes are not expected. These structures comprise multiple layers of granular material, which generally have decreasing strength with depth. Failure of these systems is typically observed as rutting on the ground surface, but the failure instigates at depth. In this research, for the first time, observations can be directly made of the progressive failure of these deeper layers under repeated wheel loading due to the combination of a new test apparatus, the Cambridge accelerated pavement tester (APT) and digital image correlation (DIC) technology. The use of a window allowing observation of soil displacements at depth during repeated wheel loading cycles allows the progressive failure to be observed and the changes in soil displacements and strains with different layer thicknesses to be quantified. It was observed that the critical failure mechanisms for thin and thick surficial layers are different, resulting in changes in the rates of surface rutting. Understanding these deformation mechanisms potentially allows savings to be made in road or airfield construction by using correctly sized structural layers.

Estimation of total fatigue life for in-service asphalt mixture based on accelerated pavement testing and four-point bending beam fatigue tests

The purpose of this study was to estimate the total fatigue life for in-service asphalt mixture fatigue with in situ accelerated pavement testing (APT) and laboratory four-point bending beam tests. On a selected expressway in Shanghai, China, a series of full-scale APT tests were conducted. During the APT tests, a portable seismic property analyzer was used to monitor the pavement deterioration through modulus reduction. An equivalent factor between the APT loading and equivalent single axle loads (ESALs) was estimated. Additionally, asphalt concrete slabs were cut from the APT test sections and then transferred to the laboratory for four-point bending beam fatigue tests. A new fatigue equation was proposed for the in-service asphalt mixtures. Furthermore, a shift factor between the laboratory fatigue life and field ESAL was recommended. Finally, the field total fatigue life of the in-service asphalt mixture was estimated based on all the work in this study.

Experimental study on the fatigue performance of pavement structures made of AAHSP

ABSTRACT Assembled aluminium honeycomb sandwich panels (AAHSP) can be used as urgent repair and construction materials for airport runways. To verify the feasibility of using this type of pavement structure, two soil test sections of different strengths were constructed and four kinds of honeycomb aluminium sandwich panels, each with different thicknesses and strengths, were laid on top of soil test sections. Then, a heavy vehicle simulator was used to perform load testing based on loading profiles associated with light and heavy aircraft. Fatigue characteristics were measured, including the overall vertical deformation (displacement) of the pavement, vertical displacement of each structural layer, relative rutting, and fatigue failure at positions between the interlocking edges and at corners of the panels. With the exception of one type of panel, all other panels meet low-sortie traffic requirements of light aircraft on single-layered or double-layered ground. Moreover, one panel was also shown to fully meet the requirements for landings and take-offs of heavy aircraft on the double-layered ground. The pavement structure demonstrated improved fatigue performance by incorporating high-stiffness aluminium honeycomb sandwich panels. Lack of friction between the soil test sections and pavement panels is the main reason large premature deformation occurred on the pavement panels of soil test sections; therefore, it is necessary to enhance the friction resistance of stabilised soil. Depressions on panels and height differences between panels can lead to rutting, which can threaten the safe operation of aircraft and cannot be ignored. Increasing the thickness of the honeycomb core was shown to reduce bending deformation of pavement panels but increased compression of the honeycomb core. Fatigue performance of panels under aircraft loads can be significantly improved by strengthening the panels around the interlocking positions, increasing the thickness of the honeycomb core structure, adding fillets to panel corners, and improving panel-honeycomb and panel-panel welding techniques.

Application of infrared thermography for debonding detection in asphalt pavements

Conventional testing practices in pavement damage surveillance and maintenance such as coring tend to be slow, destructive in nature and not wholly representative of the entire stretch of the pavement. Newly emerging technologies based on non-destructive testing techniques, do not demand implementing destructive measures or relying on extrapolation of point data and can be implemented after developing them into a proper technique and a set testing protocol. One such emerging technique that uses infrared emissions from any structure to inspect underlying defects is infrared thermography (IRT). In a patch of pavement containing subsurface defects, the heat flow to the surface of the pavement, which itself depends on the incident solar radiation, ambient temperature and other meteorological factors, gets disrupted causing a difference in the thermal signature of the defective and the sound patches. This difference in thermal signature can potentially be detected by a thermal imaging camera. This study aims at exploring the potential of IRT technique to assess the subsurface debonding defect in asphalt pavements. For this purpose, an in situ asphalt pavement test section has been constructed and different interlayer bonding conditions have been artificially induced in it. A novel way for quantitative and qualitative analyses of thermal signatures, using MATLAB for each of these bonding conditions has been carried out. The effect of different debonding agents on the overall thermal behavior of asphalt pavement has also been evaluated. Interchange time duration between day heating and night cooling cycles has been estimated, to determine the suitable time duration for asphalt pavement inspection. The results, advantages, and limitations of the method have been presented.

Guidelines for the use of accelerated pavement testing data in autonomous vehicle infrastructure research

Abstract There is much research conducted on the vehicle technologies required for operation of autonomous vehicles (AV) on public roads, as well as analysis of the interaction between AV and the road environment. However, limited research exists on the impact of AV on road pavement structures. The research includes issues such as the effect of more channelized traffic loading, shorter inter-vehicle following distances and potential higher traffic volumes of more uniform vehicle types and loads. This paper discusses the application of existing and generation of new, relevant accelerated pavement testing (APT) data in understanding the effects of AV on pavement infrastructure. The paper presents development of provisional guidelines for the use and application of APT data to ensure that road pavement structures cope with anticipated increase in AV use. It is concludes that the use of AV fleets on existing road pavement infrastructure may lead to different behaviors and responses than what became the norm under non-autonomous vehicle fleets; appropriate analysis of existing APT data will contribute to the improved understanding of these expected changes in behaviors and responses; appropriate planning of AV operations-focused APT is possible with existing technology to contribute to the provision of economic and durable road pavement infrastructure in future.

Iterative Framework for Performance and Environmental Impacts of Airfields

The main goal of a durable and sustainable airfield is to withstand repeated aircraft traffic loading while minimizing the environmental impact. The objective of this study is to develop a design-life cycle assessment (LCA) framework considering a balanced evaluation of structural adequacy, minimizing emission, and optimizing total energy demand. To achieve this objective, three steps are introduced: an evaluation of the structural adequacy of the design using the Federal Aviation Administration (FAA) pavement design software FAA rigid and flexible iterative elastic layered design; a preliminary performance check using field instrumentation responses; and a LCA of airfield sections using both deterministic and probabilistic approaches. In addition to presenting the design-LCA methodology, this paper offers a comparative evaluation that covers two perpetual designs (LFP1-N and LFP4-N) and one conventional section (LFC5-N). These pavement sections were built and tested at the National Airport Pavement Test Facility as part of construction cycle 7, funded by the FAA. Responses collected from instrumentation were used to compute field-based coverages to failure. Moreover, life cycle inventories from secondary sources were used to quantify the greenhouse gas emissions and energy demand associated with the construction of these sections. Results show inconsistencies between the field-predicted and theoretically predicted performance. This suggests the need for the additional calibration of the currently used performance models. Moreover, this study shows that under a specific asphalt concrete (AC) thickness limit, conventional AC may be more eco-friendly than a perpetual design.

Large-Scale and Bench-Scale Test Systems for Assessing Impact of Geogrids on Pavements Founded on Problematic Soils

Abstract Geogrid reinforcement is an economically viable alternative to achieve improved performance in highway pavement construction in regions with soft problematic subgrade soils. To examine the potential benefits of using geogrids in pavement foundations, measurement of permanent deformation using laboratory triaxial tests is typical practice. However, since the performance improvement of pavement foundation systems is achieved by distribution of vertical stresses at the reinforcing layer through the tensile properties of the geogrid material, it is desirable to conduct large-scale testing to more accurately monitor the behavior of the geogrid-reinforced aggregate and soil system. This article describes the development of laboratory large-scale and bench-scale pavement testing systems to evaluate the behavior of geogrid-reinforced pavement systems through wheel tests performed with problematic subgrade soils found in North Georgia. The large-scale test specimens are prepared in a 1.8 (6 ft) by 1.8 (6 ft) by 0.6 m (2 ft) metal box and consist of 305 mm (12 in.) of unbound aggregate base (UAB) overlying 305 mm (12 in.) of subgrade soil. Geogrid is placed at the interface between the subgrade soil and UAB layer. Pressure sensors are installed near the bottom of the UAB layer and near the top and bottom of the subgrade layer to monitor stress distributions within the pavement foundation system. The bench-scale system, which measures 914 (36 in.) by 203 (8 in.) by 152 mm (6 in.) is also described. This system is advantageous because not only does it expedite rapid testing but also allows for relative micro- and macroscale comparisons of aggregate-geogrid behavior. This article presents test results showing vertical stress variations obtained experimentally in the UAB and subgrade soils under simulated traffic tire loading. The two systems are shown to be effective in establishing the influence of geogrid reinforcement in pavement systems.

Full-scale validation of bio-recycled asphalt mixtures for road pavements

Recycling of asphalt has become a well-established practice in many countries, however the road pavement industry remains a bulk consumer of extracted raw materials. Novel solutions that find root in circular economy concepts and life-cycle approaches are needed in order to enable optimisation of infrastructure resource efficiency, starting from the design stage and spanning the whole value chain in the construction sector. Itis within this framework that the present study presents a full-scale validation of asphalt mixtures specifically designed to ensure durability of flexible road pavements and at the same time enabling the reuse of reclaimed asphalt pavement (RAP) through the incorporation of bio-materials as recycling agent. These bio-recycled asphalt mixtures have been first designed in laboratory and subsequently validated in a real scale experiment conducted at the accelerated pavement testing facilities at IFSTTAR. Four pavement sections were evaluated: three test sections with innovative bio-materials, and a reference section with a conventional, high modulus asphalt mix (EME2). Two tests were realized: a rutting test and a fatigue test and for each of them the evolution of bio-recycled asphalt mixtures properties as well as the pavement deteriorations were recorded and studied. Evolution of the bio-asphalt mixtures was monitored for a 5 months period after paving by a bespoke nondestructive micro-coring, extracting and recovering methodology developed at the Western Research Institute (WRI). The structural health of the pavement sections was monitored through periodic falling weight deflectometer (FWD) as well as with strain gages and temperature sensors. As a result the three tailored bio-asphalt mixtures performed similarly or better than the control mixture, both in terms of property evolutions and durability.

Analysis of airfield composite pavement responses using full-scale accelerated pavement testing and finite element method

Abstract This study focuses on the critical responses of airfield composite pavements that are composed of hot-mix asphalt (HMA) overlay and Portland cement concrete (PCC) pavement. Accelerated pavement testing (APT) and a finite element (FE) method were employed to investigate the effects of three influential factors: temperature, interface bonding, and load level. A full-scale test field was constructed for this study and instrumented with 20 strain gauges and 32 temperature sensors. A finite element model was developed based on the parameters derived from laboratory and field tests and the model was then validated through measurements. The results indicate that longitudinal strain is more critical than transverse strain in an HMA overlay when subjected to moving loads. Moreover, the results underscore that temperature significantly affects the responses of HMA overlays and that the relationship between temperature and pavement responses is sigmoidal. Furthermore, a good interface bonding is able to significantly reduce the critical strain in an HMA overlay and the interface bonding strength is very sensitive to the amount of tack coat. The positive strain near to the surface of HMA overlay is due to high compressive stress, which is different from the tensile strain used in fatigue testing.

Georadar vibration-acoustic technology for express-control of road pavement strength and results of its application

The technique of determining the pavement layers strength are given. The results of a field (on the road) testing of asphalt concrete Highway pavement using georadar vibration-acoustic set of equipment are presented. The hardware complex is proved and developed for the automobile roads express-control. Functioning of hardware complex and technique for pavement layer durability definition are described. The ways of the further perfection for the georadar vibrating-acoustic technology are considered.

Laboratory characterization of temperature induced reflection cracks

Abstract A hot-mix asphalt (HMA) overlay is one of the primary strategy for rehabilitating existing HMA pavements and Portland cement concrete (PCC) pavements. The current design program, FAARFIELD, does not address reflective cracking for asphalt-overlaid concrete pavements due to its mechanism complexity. The bending, shearing, and thermal are three crucial factors to successfully model reflective cracking. To implement this failure mode in flexible over rigid design procedure, a series of full-scale test pavements were constructed, instrumented, and tested in the condition of extreme cooling temperature at the FAA National Airport Pavement Test Facility. The purpose was to assess cooling effects on the propagation of reflection cracks for airport AC over PCC pavements. In preparation for reflective cracking phase VI test, the FAA is conducting laboratory experiment on field extracted hot mix asphalt (HMA) cores. In order to test these field HMA cores, the Texas Overlay Tester (OT) was customized to get data similar to the full-scale tests. This paper discusses finite element analysis on the full-scale testing, development of the customized Texas OT, and a laboratory testing suite using the customized Texas OT, including preliminary tests, instrumentation, experiment design, and test results. Data obtained from this research effort will be used to develop a rational testing procedure to simulate extreme cooling cycles through full-scale testing.

Development of full-scale laboratory accelerated pavement testing facility: a step toward performance assessment of geosynthetics reinforced pavement

The road network in India is growing at an exponential rate. The biggest challenge in this scenario is an availability of good-quality pavement materials at a reasonable rate. The demands of these pavement materials are increasing at an accelerated rate due to which good-quality material available in nature is getting depleted rapidly. This may create a threat to the environment in the near future. The rate of depletion may be reduced to a certain extent by adopting measures, viz. use of recycled pavement materials, stabilization of locally available poor-quality materials, and use of reinforced pavement. Assessment of such measures in a limited time is the biggest challenge. This challenge may be tackled by using full-scale accelerated pavement testing setup. However, the full-scale accelerated pavement test is not readily available. Over the globe, accelerated pavement testing setups are developed at only a few universities and research institutes. This paper presents the development details of a full-scale laboratory accelerated pavement testing setup. The calibration of the applied axle load is also presented. The developed full-scale laboratory accelerated pavement testing setup will prove opportunity to test new material/technique which will build up the confidence due to gain of knowledge. This paper also aims to investigate the variation of vertical stress and deformation at the base–subgrade interface of geotextile-reinforced and unreinforced pavement using the developed pavement testing facility.

Bio materials with reclaimed asphalt: from lab mixes properties to non-damaged full scale monitoring and mechanical simulation

Three innovative environmentally friendly pavement materials, designed with 50% of Reclaimed Asphalt and three different biomaterials (2 bio-additivated bitumens and 1 bio-binder), were produced in an industrial plant. These mixes were tested in lab and also at full scale using an Accelerated Pavement Test facility. The asphalt mix viscoelastic properties were measured in lab and their intrinsic viscoelastic response were simulated. These rheological models are used to simulate the pavement mechanical response using both elastic and viscoelastic multilayer codes. Hence, full scale measurement performed during the full scale test at an early stage (without damages) can be compared with these simulations. The overall prediction accuracy, when all the signals are considered, is between 4% and 8% for all materials. It can be concluded that material characterisation in lab as well as the selected models are well adapted to simulate actual loading state under a moving load, even for these non-conventional mixes. For temperatures lower than 25°C, elastic modelling appears to be sufficient for pavement structural design with the innovative materials tested here.

Structural Analysis for APT Sections Based on Deflection Parameters

This paper reviews the use of pavement structural condition indicators determined through deflection measurements as a means to monitor structural capacity. The deflection measurements were performed with a road surface deflectometer and a falling weight deflectometer on the various test tracks of an accelerated pavement test (APT) facility. The indicators estimation was based on the deflection data collected from different structures, and it was observed that it is feasible to improve the backcalculation analysis and help overcome some of the limitations associated with such a procedure. For this research, Radius of Curvature, AREA, Normalized AREA, BLI (Upper layers), MLI (Middle layers), and LLI (Lower layers) were the analyzed parameters. Each parameter is related to the structural condition of particular pavement layers. Therefore, the parameters allow general characterization of the pavement layers, and make it possible to detect deteriorated layers. The pavement structures were trafficked by means of an APT at the PaveLab facility at the University of Costa Rica. The deflection parameters were calculated through the APT data, showing the possible use of these indicators at the pavement management system level in Costa Rica, helping the categorization of the pavement structures in service, mainly because the parameters require few input data, and are useful where the available structural condition information is limited. The data presented in this paper show the variation of the different condition indicators throughout the service life of the analyzed pavement structures. The data are also used to compare different structures, their characteristics, and the change in their stiffness associated with damage.